Clinical evaluation of the efficacy and safety of nasturtium herb and horseradish root versus placebo in the continuous prophylaxis of recurrent uncomplicated cystitis: a double-blind randomised clinical trial

Abstract

Background and objectives

This study aimed to demonstrate the efficacy and safety of a herbal combination drug of nasturtium herb and horseradish root in the continuous prophylaxis of recurring uncomplicated cystitis.

Methods

The clinical trial was conducted as a phase III, two-armed, placebo-controlled, randomised, double-blind, prospective, and multi-center study, which followed a parallel-group design in Germany. Data were collected in a multicenter setup in Germany. Patients of either sex aged ≥ 18 years with recurring uncomplicated cystitis were considered for the study. Interventions were Nasturtium herb and horseradish root prophylaxis versus placebo. The primary outcome measure was the rate of first recurrent urinary tract infection (rUTI) observed during six months of recurrence prophylaxis in the herbal and the placebo group from day 0 to day 180. Additional efficacy outcome measures included: recurrence rates at scheduled visits during the course of recurrence prophylaxis; recurrence rates during three- and six-month follow-up and Investigator’s assessment of efficacy at completion of recurrence prophylaxis. Safety evaluation included type, frequency, and severity of reported adverse events.

Results

A total of 224 patients were enrolled, of which 217 women were included in the full analysis set. Patients were randomised to treatment with either nasturtium herb and horseradish root (N = 110) or placebo (N = 107). The cumulative recurrence rate increased for the placebo group to approximately 40% by day 90 and 48% by day 180, while the nasturtium herb and horseradish root group had lower rates of 26% and 36%, respectively. The overall risk of rUTI was reduced by 36% (hazard ratio [HR] 0.64, 95% confidence interval [CI] 0.42–0.97, p = 0.0327) in the treatment group. This effect remained consistent (although statistically insignificant) during the follow-up period up to 360 days. There were no significant differences between groups, for any of the reported adverse effects.

Conclusion

The results of this study indicate that nasturtium herb and horseradish root may be an effective, safe prophylactic treatment for female patients suffering from rUTIs.

Trial registration

This trial was registered with EudraCT under the number: EudraCT 2013-004653-25. The study was approved on 2nd of May 2014 and the first participant was enrolled on 9th of May 2014.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-026-05328-z.

Background

Urinary tract infections (UTIs) are among the most common bacterial infections, affecting approximately half of all women at some point in their lives, with high recurrence rates of 36% in women under 55 and 53% in older women within a year [1, 2]. Although more prevalent in women, UTIs also affect men, children, and commonly occur in individuals with conditions like multiple sclerosis or those using urinary catheters [3]. Uncomplicated UTIs, such as cystitis and pyelonephritis, often recur, posing significant clinical challenges.

Recurrent UTIs (rUTIs) are typically defined as having more than two episodes in six months or more than three in a year. Diagnosis is based on patient-reported symptoms such as dysuria, pollakiuria, and urinary urgency, confirmed by urine culture [2]. The predominant causative agent is uropathogenic Escherichia coli (UPEC), with other common pathogens including e.g. Klebsiella pneumoniae and Staphylococcus saprophyticus [4].

The formation of bacterial biofilms and bacterial internalisation into bladder cells are key factors in the persistence and recurrence of UTIs. These biofilms allow bacteria to evade host defenses and antibiotic treatments, leading to recurring infections and increased antibiotic resistance [4, 5].

The growing problem of antibiotic resistance necessitates alternative prophylactic treatments. Frequent and prolonged antibiotic use for rUTIs not only disrupts the human microbiota but also accelerates the development of resistant bacterial strains [6]. Current guidelines, such as those from the European Association of Urology (EAU), recommend various strategies to mitigate rUTI recurrence, including behavioral modifications, the use of vaginal estrogen, and considering alternative treatments like D-mannose and herbal remedies [2]. However, there is no single standard treatment recommended for all patients, making it challenging to compare the test treatment directly with another standard treatment.

A herbal combination of nasturtium herb and horseradish root has shown promise as a prophylactic treatment for rUTIs due to its high levels of antimicrobial isothiocyanates (ITCs). ITCs have demonstrated broad-spectrum antimicrobial activity against many clinically relevant and antibiotic-resistant pathogens in vitro [7, 8]. Furthermore, the ITCs are able to reduce bacterial motility and bacterial adhesion [9] and intraepithelial internalization processes [10] as well as bacterial biofilm formation by inhibition of quorum sensing [11]. Antimicrobial activity proven for combination of both components (nasturtium herb and horseradish root) is attributed to high levels of isothiocyanates (ITCs, mustard oils) present in the mixture [7, 8, 12]. This has been confirmed by numerous in vitro studies, which demonstrated that the combination of allyl isothiocyanate and phenylethyl isothiocyanate from horseradish root and benzyl isothiocyanate from nasturtium herb have a broad spectrum of antimicrobial activity against current clinically relevant pathogens as well as multidrug-resistant strains [7, 10]. ITCs are absorbed in the upper intestinal tract, then converted to mercapturic acids and mainly excreted renally. Mercapturic acids however, are unstable in aqueous solution due to thioester bonding and cleave in the bladder to ITCs again under pH-dependent equilibrium conditions [13]. The combination of pharmacological action of ITCs and the availability at the site of UTI indicate that the mixture of nasturtium herb and horseradish root may be an effective prophylactic treatment for patients suffering from rUTIs. The efficacy and safety of this mixture against (r)UTIs has been demonstrated through several clinical trials and other prospective cohort studies performed in adult patients and children [14–17]. The anti-inflammatory effects of the single ingredients [18–20] may also calm the excessive inflammatory host reaction via interaction with lipoxygenase and cyclooxygenase signaling pathways. Given the lack of an universally accepted standard treatment for rUTIs and the interest in evaluating new potential prophylactic options, this study aimed to compare the nasturtium herb and horseradish root mixture with a placebo to establish its efficacy and safety in preventing rUTIs in patients with recurring uncomplicated cystitis.

Methods

Study design

The study was a phase III, placebo-controlled, randomised, double-blind, prospective and multi-center clinical trial in Germany, which followed a two-arm parallel-group design. Patient recruitment was performed by doctors and took place in 57 different registered doctor practices. The aim was to evaluate the safety and efficacy of a herbal drug in the continuous prophylaxis of recurring uncomplicated cystitis. Recruitment started on May 9, 2014, and the study was finalised on August 15, 2019. Due to difficulties with recruitment, the study was terminated before it’s originally planned conclusion.

Study medication

The study medication was the nasturtium herb and horseradish root medicinal product (ANGOCIN Anti-Infekt N, owned by Repha GmbH Biologische Arzneimittel (Repha GmbH)). Each tablet consists of 200 mg Tropaeolum majus (nasturtium) herb and 80 mg Armoracia rusticana (horseradish) root, and is ingested by the patient. The placebos had same sizes and coatings, as well as identical blisters, packaging, and labeling exterior. Each box was assigned a unique number in order to be appointed to randomised patients. Both the medicine studied and the placebos were provided by the marketing authorization holder.

Patients

Patients of either sex aged ≥ 18 years with a history of recurring uncomplicated cystitis were intended to be enrolled in the study. At the time of the screening visit, an acute episode was diagnosed on the basis of clinical symptoms and verified by a positive urine culture from 10³ CFU/mL urine. “Recurrent cystitis” is defined as a history of at least three cystitis episodes in the last 12 months or at least two episodes in the last 6 months, including those present at the time of the screening visit. Symptoms included dysuria, pollakiuria, nocturia, urinary urgency, suprapubic pain and urinary incontinence. Patients who met the exclusion criteria were not eligible to take part. The following criteria were examined for exclusion in addition to the standard exclusion criteria: patients receiving prophylactic medication for infection other than the study medication, potentially prophylactic products of herbal origin, such as cranberry, rosehip, or renal bladder tea; patients who had participated or were participating in other drug trials 30 days prior to initial inclusion or during the clinical trial; existing alcohol abuse or abuse of medications or drugs; serious mental illness; individuals who had been institutionalised by governmental or court order (full list in supplementary Table 1). Potential trial subjects were approached directly by the examiners at the test centers and asked about their willingness to participate (Fig. 1).

Fig. 1.

Flow diagram of patient numbers. Some patients were excluded from the PP set for more than one reason

Trial procedures

All patients who gave written informed consent to participate in the clinical trial, were enrolled at visit 1 (day − 11). For further participation in the trial, the investigator had to diagnose the healing of the acute episode based on symptoms as well as on central laboratory by the presence of a negative urine culture (visit 2). At visit 3 (day 0), randomisation was performed for all subjects who were eligible for further participation in the clinical trial according to the in- and exclusion criteria. The randomisation of the patients was done in a 1:1 ratio (verum: placebo). In this manner, both, patients and investigators were blind to the sort of medication given.

The study was divided into three phases with 15 visits, some of which were by telephone: Phase I: Screening phase − 25 days; Phase II: Recurrence prophylaxis − 6 months; Phase III: Follow-up − 6 months. In case of suspected recurrence, replacement visits were scheduled. There was a minimum of seven and a maximum of ten days between completion of therapy for the acute episode and monitoring of therapy (visit 2). Visit R-S (between visits 1 and 3) replaced visit 3 if the symptoms did not subside adequately within 10 days after visit 1. Visit R-P (between visit 3 and visit 9) replaced visit 9 if recurrence was suspected during recurrence prophylaxis. Visit R-F (between visit 9 and visit 15) replaced visit 15 if recurrence was suspected during follow-up (Fig. 2).

Fig. 2.

Schematic overview of the study procedure. Patient inclusion after signing the informed consent at visit 1

Patients were given a patient diary at visits 3, 6, and 9. During rounds 3 and 9, a member of the study team explained to the subjects how to complete the patient diaries. The participant was asked to return the completed diary to the investigator at the following visits in the study center (visits 6, 9, 15). When the diary was returned, the investigator checked the entries, discussed ambiguities, missing information and undesirable events with the subject and, if necessary, had the subject concerned make corrections and additions. Adverse events that were reported to the investigator through the diary were to be evaluated by the investigator and documented in the source data and in the electronic Case Report Form.

The full trial protocol can be accessed at https://www.clinicaltrialsregister.eu/ctr-search/search?query=repha_1362.

Changes made after trial commencement

Due to challenges in patient compliance and recruitment, a decision was made to reduce the follow-up duration for newly randomized patients. Specifically, follow-up for these patients was discontinued, and ongoing participants entered a shortened 3-month observation period instead of the originally planned 6 months. Adjustments were made to the study visit schedule in order to accommodate these changes. In addition, enrollment was halted before the planned number of participants was reached.

Due to various logistical issues, including improper sample collection and patients’ inability to provide samples (while for example on holiday), the urine sample to culture for confirmation of recurrence were only available for a limited number of patients. A decision was therefore made to amend the protocol, to include all patients who self-reported urinary tract infections (UTIs), even if these were not confirmed by laboratory tests as initially required by the protocol.

It should also be mentioned, that while the initial study included both male and female patients, only the female data is reported here. This is due to a very small number of male participants, which could make a generalization of the complete data set to all sexes misleading.

The modifications aimed to prioritize the evaluation of data already collected while ensuring compliance with Good Clinical Practice (GCP) standards.

Patient time schedule

Screening phase duration was 25 days. The medication intake lasted 180 days and the follow-up another 180 days. The duration for each patient was a maximum of 12 months and 3 weeks, with a total of 15 visits.

Randomisation

Random allocation was performed by the statistician in charge, documented in a randomisation list and in individually sealed emergency envelopes. The block size was 4. The study medication was packaged accordingly and labelled with the randomisation number. Statistician and manufacturer were obliged to maintain confidentiality. All other persons involved in the trial did not have access to the randomisation list and were therefore blinded to the group allocations. The original was kept sealed by Mediconomics GmbH and only released again for the evaluation of the clinical trial.

Treatment

At visit 3 (randomisation), patients received the study medication for the first 3 months of prophylaxis and at visit 6 for the last 3 months. Patients took 4 film-coated tablets 3 times daily for 6 months (180 days). For the test group, all blisters were filled with the drug containing nasturtium herb and horseradish root and for the comparison group with placebo (identical appearance).

Primary outcome measure

The primary outcome measure was the rate of first recurrent urinary tract infection (rUTI) observed during six months of recurrence prophylaxis in the herbal and the placebo group from day 0 to day 180. Recurrences were defined as symptomatic infections with a central laboratory-confirmed uropathogenic germ count of ≥ 10³ CFU/mL urine in pure culture.

Secondary outcome measure

Additional efficacy outcome measures are listed below:

• Recurrence rates at scheduled visits during the course of recurrence prophylaxis (visit 4–8).

• Recurrence rates during three- and six-month follow-up (days 180 to 270 and 360).

• Investigator’s assessment of efficacy at the completion of recurrence prophylaxis (visit 9 or Visit R-P).

• Investigator’s assessment of continued efficacy of the study medication beyond the completion of prophylaxis at the end of follow-up (visit 15 or visit R-F).

• Results of pathogen testing in case of recurrence with positive urine culture detected during the prophylaxis period.

Safety evaluation included type, frequency, and severity of reported adverse events. For the determination of safety parameters, subjects were given blood tests at visits 1, 3, 6 and at the end of the prophylaxis phase (visit 9 or visit R-P) using established and standardised techniques.

Observations of vital signs during the course of the prophylaxis phase included pulse, blood pressure and body temperature. Furthermore, tolerability of the study medication was assessed in the course of prophylaxis weekly by the patient in the diary and at the end of the prophylaxis phase by the investigator. Finally, the potential effect of menopausal status was analysed.

Statistical analysis

Statistical analysis was performed using SAS software, version 9, and the R system, version 4.1 (http://cran.r-project.org). SPSS version 22 was used to replicate the analyses. Means and standard deviation for continuous data, as well as frequencies and percentages (e.g., for incidence rates) were calculated for discontinuous data. Primary outcome measures were the rate of first recurrence R and V in the test group and in the comparison group, respectively, over the course of 180 days of relapse prophylaxis, determined as Kaplan-Meier estimators (product limit estimators). The recurrence rates were compared by log-rank test. Hazard ratios and 95% confidence intervals were calculated using univariate Cox proportional hazards models. In addition, Fisher’s exact test and Chi² tests were used to quantify group differences in categorical data. For continuous data, the Mann-Whitney test was used. The analysis for the main outcome parameter (recurrence rates in 2-group comparison by log-rank test) was performed at an unadjusted α = 0.05, and all other descriptive comparisons were performed at the threshold of p = 0.05.

The sample size estimate assumed a high recurrence probability of approx. 60% in 6 months. With nasturtium herb and horseradish root 3 × 4 film-coated tablets, a recurrence rate of approx. 40% and thus a reduction of 20% points was expected. To significantly separate the 6-month rates 40%, and 60%, in the log-rank test at a dropout rate of 10%, 112 patients per group were needed if a power of 1-β = 0.8 was to be achieved [16, 21]. The total number of cases was therefore 224 (an assumption), feasible e.g. in 20 centers with 12 patients each.

Results

Patient analysis sets

In total, 224 patients met the inclusion criteria and were randomised. Of these, one patient withdrew consent after visit 3 (patient did not attend). The samples of two other patients were lost and they were therefore excluded from the study. As over 98% of the included patients were women, the decision was made to exclude male subjects from analysis, and to present results for females only. This was because the inclusion of males did not change the outcomes of the study, but it would be unreasonable to apply conclusions based on these combined results to male patients.

A total of 217 female patients received the study medication and were evaluated as a full analysis set (FAS). Of these patients, 110 received the treatment and 107 received placebo. A further 66 patients were excluded from the per-protocol (PP) collective, due to protocol violations such as contaminated urine cultures. The remaining 151 patients formed the PP collective (82 and 69 patients in the treatment and placebo groups respectively).

Patient demographics

The ages of female patients included in the FAS did not differ between groups (p = 0.959). All subjects had experienced a total of at least 3 UTIs in the last 12 months, with at least two of these being in the last 6 months. The prevalence of previous interventions and comorbidities were recorded and are listed in the table below (Table 1). The most common comorbidities reported were reproductive system and breast disorders (12.4% and 22.4% of patients in the treatment and placebo group respectively), and infections and infestations (20.2% and 16.4% for treatment and placebo respectively). No differences were found between groups.

Table 1.

Female Patient Demographics and comorbidities

Demographic Charactristic	Treatment Group (N = 110)	Placebo Group (N = 107)	Total (N = 217)
Age (years)	50.40 ± 20.00	50.26 ± 19.34	50.33 ± 19.63
Ethnicity
White	109	106	215
Other	1	1	2
Hormonal factors
Hormonal Contraceptives	29 (26.4%)	29 (27.1%)	58 (26.7%)
Hormonal coil (IUS)	1 (0.9%)	2 (1.9%)	3 (1.4%)
Hormonal and mechanical contraception	6 (5.5%)	7 (6.5%)	13 (6.0%)
Post-Menopausal	29 (26.4%)	31 (29.0%)	60 (27.6%)
Comorbidities (based on system organ class)
General disorders and administration site conditions	1 (1.1%)	0 (0.0%)	1 (0.6%)
Eye disorders	2 (2.2%)	0 (0.0%)	2 (1.3%)
Surgical and medical procedures	6 (6.7%)	9 (13.4%)	15 (9.6%)
Endocrine disorders	6 (6.7%)	1 (1.5%)	7 (4.5%)
Respiratory, thoracic and mediastinal disorders	2 (2.2%)	0 (0.0%)	2 (1.3%)
Reproductive system and breast disorders	11 (12.4%)	15 (22.4%)	26 (16.7%)
Renal and urinary disorders	4 (4.5%)	2 (3.0%)	6 (3.8%)
Gastrointestinal disorders	4 (4.5%)	2 (3.0%)	6 (3.8%)
Nervous system disorders	5 (5.6%)	6 (9.0%)	11 (7.1%)
Vascular disorders	1 (1.1%)	0 (0.0%)	1 (0.6%)
Neoplasms benign, malignant and unspecified (including cysts and polyps)	14 (15.7%)	9 (13.4%)	23 (14.7%)
Cardiac disorders	2 (2.2%)	1 (1.5%)	3 (1.9%)
Infections and infestations	18 (20.2%)	11 (16.4%)	29 (18.6%)
Congenital, familial and genetic disorders	1 (1.1%)	2 (3.0%)	3 (1.9%)
Hepatobiliary disorders	2 (2.2%)	1 (1.5%)	3 (1.9%)
Psychiatric disorders	1 (1.1%)	0 (0.0%)	1 (0.6%)
Musculoskeletal and connective tissue disorders	5 (5.6%)	3 (4.5%)	8 (5.1%)
Metabolism and nutrition disorders	1 (1.1%)	1 (1.5%)	2 (1.3%)
Investigations	0 (0.0%)	1 (1.5%)	1 (0.6%)
Injury, poisoning and procedural complications	3 (3.4%)	3 (4.5%)	6 (3.8%)

Treatment compliance

To quantify intake compliance, the difference between the tablets taken and the tablets handed out was calculated. A compliance rate less than 85% was observed in 15 patients and assessed as major protocol violation that resulted in exclusion from the PP collective. Statistical differences were not found between the two treatment groups. In addition, due to various logistical issues, including improper sample collection and patients’ inability to provide samples (while for example on holiday), only 162 out of 217 patients (75%) were able to supply a urine sample to culture for confirmation of recurrence.

Treatment efficacy

The primary target parameter (the cumulative rate of first UTI recurrences) was calculated for the females of the FAS using Kaplan-Meier analysis. Here, the treatment showed a clear and significantly flatter course of the cumulative risk of recurrence compared to placebo, with general risk of a rUTI decreased under treatment by a factor of 0.64, i.e. by 36% (OR of Cox regression, 95% CI 0.42–0.97, p = 0.0327) (Fig. 3). This effect is similar when the PP collective is analysed with the general risk of a UTI recurrence being reduced by a factor of 0.59, i.e. by 41% (95% CI 0.37–0.94, p = 0.024) in the treatment group (supplementary Fig. 2).

Fig. 3.

Cumulative recurrence rate of urinary tract infections (± 95%CI) in FAS of female patients receiving nasturtium herb and horseradish root (red; N = 110) and placebo (blue; N = 107) treatments over the 180 days treatment period. Analysis was performed by log-rank test at an unadjusted α = 0.05. All statistics are descriptive

In terms of secondary parameters, the difference between the number of patients experiencing rUTIs in the treatment and placebo groups was assessed for each 30-day time frame individually. In this analysis, the nasturtium herb and horseradish root FAS group showed a significantly reduced risk of absolute recurrence from day 90 in the FAS (p = 0.030, OR = 1.892 [1.061; 3.375]), with a tangential decrease at day 120 (p = 0.119, OR = 1.550 [0.892; 2.693]), day 150 (p = 0.091, OR = 1.597 [0.926; 2.754]) and day 180 (p = 0.068, OR = 1.658 [0.962; 2.754]) (Table 2). Similar results were found when analysing the PP group, which showed a significant difference between treatment and placebo from day 90 onwards (data not shown).

Table 2.

rUTI at fixed points for the whole length (days 0–360, women only, FAS, statistical test: Chi²-test, all tests are descriptive)

First rUTI	rUTI	Total N = 217		Treatment N = 110		Placebo N = 107		Chi²-test	Odds-Ratio
		n	%	n	%	n	%
within 30 d	-	193	88.9	96	87.3	97	90.7	p = 0.427	OR = 0.707 [0.299; 1.669]
	+	24	11.1	14	12.7	10	9.3
within 60 d	-	159	73.3	84	76.4	75	70.1	p = 0.297	OR = 1.378 [0.754; 2.522]
	+	58	26.7	26	23.6	32	29.9
within 90 d	-	147	67.7	82	74.5	65	60.7	p = 0.030	OR = 1.892 [1.061; 3.375]
	+	70	32.3	28	25.5	42	39.3
within 120 d	-	135	62.2	74	67.3	61	57.0	p = 0.119	OR = 1.550 [0.892; 2.693]
	+	82	37.8	36	32.7	46	43.0
within 150 d	-	128	59.0	71	64.5	57	53.3	p = 0.091	OR = 1.597 [0.926; 2.754]
	+	89	41.0	39	35.5	50	46.7
within 180 d	-	127	58.5	71	64.5	56	52.3	p = 0.068	OR = 1.658 [0.962; 2.754]
	+	90	41.5	39	35.5	51	47.7
within 210 d	-	123	56.7	68	61.8	55	51.4	p = 0.122	OR = 1.531 [0.892; 2.627]
	+	94	43.3	42	38.2	52	48.6
within 240 d	-	119	54.8	65	59.1	54	50.5	p = 0.202	OR = 1.418 [0.829; 2.425]
	+	98	45.2	45	40.9	53	49.5
within 270 d	-	113	52.1	61	55.5	52	48.6	p = 0.312	OR = 1.317 [0.772; 2.246]
	+	104	47.9	49	44.5	55	51.4
within 300 d	-	113	52.1	61	55.5	52	48.6	p = 0.312	OR = 1.594 [0.772; 2.246]
	+	104	47.9	49	44.5	55	51.4
within 330 d	-	110	50.7	59	53.6	51	47.7	p = 0.379	OR = 1.270 [0.745; 2.165]
	+	107	49.3	51	46.4	56	52.3
within 360 d	-	107	49.3	56	50.9	51	47.7	p = 0.633	OR = 1.139 [0.669; 1.940]
	+	110	50.7	54	49.1	56	52.3

“+” = rUTI; “-“ = no rUTI, including censored patient

This effect was diminished in the follow-up period (days 210–360), with 58% and 65% of FAS treatment and placebo group patients experiencing recurrence at the end of the study respectively (p = 0.633, OR = 1.139 [0.669; 1.940]) (Table 2). It should be noted that since the primary endpoint assessed only time to the initial recurrence, patients were no longer followed up with after this had occurred, and were therefore included in the ‘censored’ group.

At the end of the treatment period (day 180), 64.5% of female patients in the FAS treatment group remained rUTI free, compared to 52.3% in the placebo group. This difference was present until the end of the follow up periods, with 42% and 35% of patients remaining recurrence free in the treatment and placebo groups respectively (Table 2).

The mean time to first recurrence was calculated as being 246.8 days in the treatment group (SE = 17.0 days), while the placebo group patients experienced a recurrence after an average of 199.9 days (SE = 18.4 days) (supplementary Fig. 1).

Urine samples from patients with rUTIs were collected and analysed. The determined spectrum of bacteria was comparable to data described in the literature [4]. UPEC dominated in 70% of the collected samples, followed by Klebsiella pneumoniae (6,7%), Enterococcus faecalis (5,6%), Proteus mirabilis (3,3%), Enterococcus spec. (3,3%) Pseudomonas aeruginosa (2,2%) Streptococcus agalactiae (2,2%) and other bacteria (6,7%).

Effect of menopausal status

Due to the known link between estrogen and UTI susceptibility, the authors assessed the potential effect of patient menopausal status on the primary outcome. Similar numbers of pre- and post-menopausal women were included in the treatment (81 (73.6%) and 29 (26.4%) respectively) and placebo (76 (71.0%) and 31 (29.0%) respectively) groups (p = 0.668, OR = 1.139 [0.628; 2.066], Table 1). In order to assess the potential effect on the rate of first recurrence, menopausal and non-menopausal patients from the treatment and placebo groups were plotted and compared in a log-rank test, followed by a cox proportional hazard model, including treatment, menopausal status and an interaction term between treatment and menopausal status. The model included all 217 female patients, and had a coefficient of determination (R²) of 0.0226. Results showed the model to be non-statistically significant overall (p = 0.1739) with an accuracy of 0.46, true positive rate of 0.05 and true negative rate of 0.75. The positive and negative predictive values are 0.14 and 0.52 respectively (Table 3).

Table 3.

Effects of menopausal status on predictors (Cox-Regression) All statistics are descriptive

	p-Value	Hazard-Ratio	lower 95%-CI	upper 95%-CI	Estimate	SE	z-Value	n
treatment	0.054	1.626	0.991	2.668	0.486	0.253	1.925	217
in menopause	0.645	1.417	0.322	6.227	0.348	0.756	0.461	217
Treat_x_menopause	0.770	0.873	0.353	2.161	-0.135	0.462	-0.293	217

Safety and tolerability

In 11 patients, the adverse events were assessed as being serious; this included 5 patients in the nasturtium herb and horseradish root group and 6 in the placebo group (see Table 4 below). These cases were assessed individually, with none of them showing a causal relationship with the study medication. No serious adverse events occurred in the male patients.

Table 4.

Table of serious adverse events during study

Patient Number	Serious Adverse Events (Verbatim)	Onset	Resolution	Group	Causal Relationship
09–013	Benzodiazepine intoxication for suicidal attempt	2016-01-03	2016-01-12	Treatment	Not related
07–008	Left lumboischialgia with spinal stenosis L4/5	2016-04-07	2016-08-12	Placebo	Not related
08−001	Descensus uteri POPQII with mixed cystocele with severe pulsation anil POPQ II-III	2015-08-12	2015-09-04	Placebo	Not related
16−001	Anaemia	2014-11-27		Treatment	Not related
	Stenosing colon carcinoma in the area of the right flexure	2014-11-27	2015-01-07	Treatment	Not related
15–024	Renal cell carcinoma	2017-01-03	2017-01-16	Placebo	Not related
22−002	Urosepsis	2015-05-07	2015-05-20	Placebo	Not related
23−012	Depression	2016-03-07	2016-03-11	Treatment	Not related
16−013	Cholangitis	2016-01-02	2016-01-30	Treatment	Not related
37−004	Metal removal from the left wrist	2016-12-01	2016-12-02	Placebo	Not related
07–011	Left heart catheterisation for angina pectoris	2017-09-29	2017-09-30	Treatment	Not related
46−002	Torn ligament	2017-01-05	2017-08-01	Placebo	Not related

The patients in the treatment group had an average of 3.7 ± 4.5 adverse events during the study, while patients in the placebo group had an average of 3.0 ± 3.2. This difference is not statistically significant (p = 0.651). The adverse effects which occurred most commonly in both were gastrointestinal disorders and infections and infestations.

Overall, around 60% of adverse events were evaluated as being unrelated to the treatment. In the treatment and placebo groups, 14% and 15.7% of events were assessed as being unlikely to be causally related to the treatment respectively, with a further 9.8% and 15.4% categorised as being possibly causally related, 1.5% and 4.3% as probably causally related and 1.2% and 0% with confirmed causality.

In total, 25 patients in the treatment group (22.7%) and 22 patients in the placebo group (20.6%) had no adverse events (AEs) in the course of the study (p = 0.651). It should be noted that while the overall rate of adverse events is relatively high, this can be reasonably attributed to the long investigation period, which increased probability of illnesses, accidents and side effects (Table 5).

Table 5.

Table of adverse events reported by female patients during study, statistics are descriptive

Adverse Event SOC	Treatment Group n (%) (N = 110)	Placebo Group n (%) (N = 107)	Total n (%) (N = 217)	Chi² test
Blood and lymphatic system disorders	1 (0.9%)	2 (1.9%)	3 (1.4%)	p = 0.545, OR = 2.076 [0.185; 23.241]
Cardiac disorders	2 (1.8%)	4 (3.7%)	6 (2.8%)	p = 0.388, OR = 2.097 [0.376; 11.696]
Ear and labyrinth disorders	4 (3.6%)	1 (0.9%)	5 (2.3%)	p = 0.185, OR = 0.250 [0.027; 2.274]
Endocrine disorders	1 (0.9%)	0 (0%)	1 (0.5%)	p = 0.323
Eye disorders	2 (1.8%)	0 (0%)	2 (0.9%)	p = 0.161
Gastrointestinal disorders	40 (36.4%)	41 (38.3%)	81 (37.3%)	p = 0.766, OR = 1.087 [0.627; 1.885]
General disorders and administration site conditions	13 (11.8%)	9 (8.4%)	22 (10.2%)	p = 0.406, OR = 0.685 [0.280; 1.677]
Hepatobiliary disorders	1 (0.9%)	0 (0%)	1 (0.5%)	p = 0.323
Immune system disorders	5 (4.5%)	1 (0.9%)	6 (2.8%)	p = 0.105, OR = 0.198 [0.023; 1.725]
Infections and infestations	63 (57.3%)	52 (48.6%)	115 (53.0%)	p = 0.201, OR = 0.705 [0.413; 1.205]
Injury, poisoning and procedural complications	6 (5.5%)	11 (10.3%)	17 (7.8%)	p = 0.186, OR = 1.986 [0.707; 5.578]
Investigations	10 (9.1%)	10 (9.3%)	20 (9.2%)	p = 0.948, OR = 1.031 [0.411; 2.587]
Metabolism and nutrition disorders	3 (2.7%)	5 (4.7%)	8 (3.7%)	p = 0.447, OR = 1.748 [0.407; 7.505]
Musculoskeletal and connective tissue disorders	20 (18.2%)	18 (16.8%)	38 (17.5%)	p = 0.792, OR = 0.910 [0.452; 1.834]
Neoplasms benign, malignant and unspecified (including cysts and polyps)	1 (0.9%)	1 (0.9%)	2 (0.9%)	p = 0.984, OR = 1.028 [0.063; 16.653]
Nervous system disorders	22 (20.0%)	15 (14.0%)	37 (17.1%)	p = 241, OR = 0.652 [0.318; 1338]
Pregnancy, puerperium and perinatal conditions	1 (0.9%)	1 (0.9%)	2 (0.9%)	p = 0.984, OR = 1.028 [0.063; 16.653]
Psychiatric disorders	7 (6.4%)	6 (5.6%)	13 (6.0%)	p = 0.814, OR = 0.874 [0.284; 2.691]
Renal and urinary disorders	14 (12.7%)	15 (14.0%)	29 (13.4%)	p = 0.780, OR = 1.118 [0.511; 2.445]
Reproductive system and breast disorders	5 (4.5%)	4 (3.7%)	9 (4.1%)	p = 0.766, OR = 0.816 [0.213; 3.123]
Respiratory, thoracic and mediastinal disorders	12 (10.9%)	6 (5.6%)	18 (8.3%)	p = 0.157, OR = 0.485 [0.175; 1.344]
Skin and subcutaneous tissue disorders	4 (3.6%)	8 (7.5%)	12 (5.5%)	p = 0.216, OR = 2.141 [0.625; 7.334]
Surgical and medical procedures	3 (2.7%)	3 (2.8%)	6 (2.8%)	p = 0.973, OR = 1.029 [0.203; 5.214]
Vascular disorders	4 (3.6%)	3 (2.8%)	7 (3.2%)	p = 0.729, OR = 0.764 [0.167; 3.499]

Clinical findings, laboratory values and vital signs showed no relevant differences between the treatment groups. AEs over the six-month study period were essentially not causally related to treatment with nasturtium herb and horseradish root. Therefore, it can be concluded that the tolerability of nasturtium herb and horseradish root is very good. The entries in the patient diaries also indicate a good overall tolerability.

Discussion

Nasturtium herb and horseradish root has been approved for use in acute respiratory and urinary tract infections in Germany since 2005. It is also mentioned in the German S3-guideline for the use in uncomplicated rUTIs [22]. Antimicrobial properties of the combination are mainly attributed to the presence of the ITCs [8]. This has been confirmed by in vitro studies, which show efficacy against a broad spectrum of clinically relevant disease-causing bacteria, including antibiotic-resistant strains [7, 12]. Furthermore, the ITCs reduce bacterial motility and bacterial adhesion in vitro [9], inhibit intraepithelial internalisation processes [10], and bacterial biofilm formation by inhibiting quorum sensing as well as mature biofilms [11]. The anti-inflammatory effects of the single ingredients [18–20] may also calm the excessive inflammatory host reaction via interaction with lipoxygenase and cyclooxygenase signaling pathways. Finally, the metabolic breakdown of ITCs results in a high bioavailability in the bladder, at the site of UTIs [13]. Taken together, these properties indicate that nasturtium herb and horseradish root may be effective in the prophylactic treatment of rUTIs.

This two-arm placebo-controlled, double-blind, multi-center superiority trial was conducted to determine whether nasturtium herb and horseradish root can reduce the relative risk of UTI recurrences. It could be clearly demonstrated that intake of the drug significantly reduced the time to first recurrence (p = 0.0327, OR = 0.64 [0.42 to 0.97]). The incidence of an initial recurrence of urinary tract infections during the prophylaxis phase was reduced to 35.5% with nasturtium herb and horseradish root compared to 47.7% with placebo (day 180). The difference between the groups became significant on day 90 and remained consistent until the end of the study period (although not statistically significant). In addition, the difference remained during the entire follow-up period (day 180 to 360), but was no longer as strong as in the prophylaxis phase (supplementary Fig. 1). The mean time to first recurrence was calculated as being 131.7 days and 112.6 days in the treatment and placebo groups respectively during the prophylactic period (day 0 to 180) and 246.8 days and 199.9 days in treatment and placebo groups respectively during the overall study (day 0 to 360). Furthermore, a possible influence of the menopausal status could be excluded.

However, there are several methodological limitations to consider. First, the study relied on patient self-diagnosis of UTI recurrence based on symptoms, which were intended to be confirmed by urine culture analysis. Due to various logistical issues, including improper sample collection and patients’ inability to provide samples while on holiday, only 162 out of 217 female patients (75%) had laboratory urine cultures. The lack of urine culture confirmation in many cases might have introduced some diagnostic inaccuracies. The statistician had specifically addressed this issue and found that there was a balance. The European Association of Urology guidelines state that the diagnosis of uncomplicated cystitis can be made with a high probability based on a focused history of lower urinary tract symptoms [2]. Furthermore, regarding symptoms and signs, new-onset dysuria, urinary urgency, urinary frequency as well as symptom recognition (i.e., patient recognises symptoms as UTI) were voted most indicative for UTI by several experts [23]. Based on these recommendations, the authors carried out statistical testing on reported symptoms supported by confirmatory medical diagnosis. The patients included in the study were all known to present with typical symptoms and had responded to appropriate antibiotic therapy before starting prophylaxis, suggesting that the lack of urine cultures may not significantly affect the results. The results obtained from analysis of the FAS were also confirmed for all outcomes by evaluation of the PP collective, which excluded all patients whose diagnosis was not confirmed by a positive urine culture due to contamination or unavailability. It is important to note that patients were included in the study based on inclusion and exclusion criteria and a confirmed diagnosis of chronic urinary tract infection, and that every participating physician is aware of lower urinary tract infections. However, specifically, the investigation did not encompass other types of disease, such as lower urinary tract dysfunction (LUTD), which should be considered in subsequent research. It is also important to note that analysis of vaginal microbiology status was not carried out due to the setting of the study. This could be a suitable co-factor for future studies.

Although the study was initially intended to include both sexes, the low number of male participants means that the outcomes of the analysis cannot reasonably be assumed to apply to men. Therefore, the male participants were excluded from analysis and the results are shown for female subjects only.

In addition, the study’s reliance on patient diaries and self-reporting could introduce bias, particularly in adherence to the treatment regimen and reporting of symptoms. This was mitigated as far as possible by the inclusion of confirmatory medical diagnosis using test strips.

Finally, the relatively short follow-up period of six months limited the ability to assess the long-term efficacy and safety of the treatment. Additional studies should include longer follow-up periods with larger and more diverse sample sizes, to provide more robust data on recurrence rates and long-term side effects.

The analysis of clinical findings, laboratory values, AEs and vital signs also showed that nasturtium herb and horseradish root is safe for long-term use. While some AEs were reported, these were mostly not causally related to the treatment and can be assumed to be due to the long investigational period. Furthermore, analysis showed no significant differences to the placebo group. A good tolerability was suggested in the patient diaries. In conclusion, a very good overall tolerability of nasturtium herb and horseradish root can therefore be confirmed.

This is important as many patients have regular recurrences, which causes a psychosocial burden and can have a serious impact on quality of life. There are currently very few other alternatives to long-term low-dose antibiotic treatment for these patients. While effective, antibiotics can have serious side effects and damage the human microbiota. A further factor to consider is antibiotic resistance, which is accelerated by frequent or long-term prescription of antibiotics [4, 24]. Therefore, alternative treatments are widely sought after and of high interest to both patients and healthcare professionals.

While other natural treatments such as cranberry, probiotics, and mannose have been suggested to have beneficial effects [22], study results remain mixed and they are currently not strongly recommended by guidelines such as the European guideline on urological infections [2]. In addition, there are other non-antibiotic options for prophylaxis mentioned in the guidelines that can serve as standardised prophylaxis, such as OM-89 as an immunoprophylaxis [22, 25] or MV140 a sublingual bacterial preparation of whole-cell inactivated bacteria [22]. The latter in particular showed very promising results in a clinical study. Compared to women who were treated with a placebo and remained free of recurrent urinary tract infections in 25% of cases, 58% of women treated with MV140 remained free of rUTIs [26]. Furthermore, a randomised controlled trial demonstrated that methenamine hippurate administered twice daily is non-inferior to daily antibiotic prophylaxis. Methenamine hippurate is a urinary antiseptic that is used as a non-antibiotic prophylactic measure for people with rUTIs [27]. For post-menopausal women, vaginal estrogen therapy has been shown to have positive effects and is recommended by European Association of Urology. The results of this study indicate that nasturtium herb and horseradish root could offer a natural treatment for rUTIs, which is highly tolerable and provides effective relief from recurrent episodes of uncomplicated rUTI. Further studies with larger sample sizes and longer follow-up periods are warranted to confirm these results and to explore the long-term benefits and safety of this treatment.

Conclusion

This phase III, randomised, double-blind, placebo-controlled study demonstrates that the herbal combination of nasturtium herb and horseradish root is an effective and safe prophylactic treatment for female patients with recurring uncomplicated cystitis. The significant reduction in the recurrence rates of UTIs in the treatment group compared to the placebo group highlights the potential of this herbal intervention as an alternative to traditional antibiotic prophylaxis. Additionally, the comparable safety profiles between the treatment and placebo groups suggest that nasturtium herb and horseradish root are well-tolerated.

The findings are particularly relevant in the context of growing antibiotic resistance and the need for alternative treatments for rUTIs. In addition, these results may be beneficial for many patients who experience regular recurrences, which can cause psychosocial burden and have a serious impact on quality of life. Despite the encouraging results, further studies with larger sample sizes and longer follow-up periods are warranted to confirm these results and to explore the long-term benefits and safety of this treatment. The potential for nasturtium herb and horseradish root to become a widely recommended prophylactic treatment in clinical guidelines should be investigated further.

Abbreviations

AE

Adverse event

CI

Confidence Interval

CFU

Colony-forming unit

EAU

European Association of Urology

FAS

Full Analysis Set

HR

Hazard Ratio

ITC

Isothiocyanate

OR

Odds Ratio

PP

Per-Protocol

SOC

System Organ Class

UPEC

Uropathogenic Escherichia coli

UTI

Urinary tract infection

rUTI

Recurrent urinary tract infection

Authors’ contributions

The guarantor of the study is (Uwe Albrecht / UA); accepts full responsibility for the finished work and/or the conduct of the study, had access to the data, and controlled the decision to publish. Uwe Albrecht is the project manager of the CRO responsible for the clinical trial, and designed the study. The principle investigator of the study was Gregor Schmitz, and clinical advice and additional supervision was supplied by Ruth Kirschner-Hermanns. Ulrich Stefenelli was the statistician for the study, and provided the data set and all analysis. Data management was performed by Lukas Schablauer. The publication was written and revised by Niklas Lonnemann and Lisa Felix, and was reviewed by all authors excluding Ulrich Stefenelli. In addition, Niklas Lonnemann acted as the regulatory coordinator and Meinolf Wonnemann and Nina Kassner participated in review and revision.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Repha GmbH acted as the financial sponsor for this clinical trial. The trial was designed, developed and prepared for publication by Mediconomics GmbH on behalf of Repha GmbH.

Data availability

All relevant anonymised patient level data will be made available upon reasonable request in accordance with the ICMJE guidelines for data sharing. This includes ensuring that data is shared in a manner that is transparent, ethical, and respects patient confidentiality. Data can be accessed by contacting the corresponding author. The full trial protocol and statistical analysis plan are also available at the clinical trial registry [https://www.clinicaltrialsregister.eu/ctr-search/search?query=repha_1362].

Declarations

Ethics approval and consent to participate

This trial was registered with EudraCT under the number: EudraCT 2013-004653-25. The EudraCT number 2013-004653-25 has been issued for your Sponsor’s Protocol Code Number Repha_1362 on 28th of October 2013. Ethical approval was granted by the Ethics Committee of the Medical Association of Westphalia-Lippe and the Medical Faculty of the Westphalian Wilhelms University Münster, ID: 2014-088-f-A. The study was approved on 2nd of May 2014. The study protocol, patient information, and informed consent form were all authorised by the German Federal Institute for Drugs and Medical Devices and registered with the competent authority (EudraCT 2013-004653-25). Prior to the investigation, written informed consent was obtained from all patients. This clinical trial was conducted in accordance with the ethical principles of Good Clinical Practice (GCP), which has its origins in the Declaration of Helsinki, and in strict compliance with the German Medicines Act (AMG), the GCP Regulation (GCP V) and the German Federal Data Protection Act (BDSG). This ensures that the rights, safety and well-being of patients are protected and that the results of the clinical trial are credible.

Consent for publication

Not applicable.

Competing interests

Repha GmbH commissioned Mediconomics GmbH as a full service CRO with planning, conduct, analysis and reporting of this clinical trial regarding an authorised medicinal product. This manuscript reports the results of the clinical trial and is intended to publish up to date medical evidence.This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Repha GmbH acted as the financial sponsor for this clinical trial. The trial was designed, developed and prepared for publication by Mediconomics GmbH on behalf of Repha GmbH.