Unexplored Factors in Medication Wastage: Investigating Economic Impact in a Brazilian Teaching Hospital

ABSTRACT

Rationale

Medication wastage is a persistent challenge in healthcare systems, yet the economic impact of syringe dead space (DS) and residual volume during routine medication administration remains underexplored outside the vaccine context.

Aims and Objectives

To investigate the economic impact of syringe dead space and residual volume on medication administration in a Brazilian teaching hospital.

Method

A retrospective observational study was conducted using medication prescription data from 2022 at the Hospital de Clínicas da Universidade Federal do Triângulo Mineiro, Brazil. All injectable medications were included. Medication cost per millilitre was calculated using hospital procurement records. Syringe sizes were defined according to prescribed volumes. Syringe dead space was measured using an analytical balance (ATY224, Shimadzu, Japan), and wasted volumes and financial losses were estimated. The medication wastage rate was calculated as the ratio between wasted value and total medication expenditure.

Results

A total of 120 medications met the inclusion criteria, accounting for 693,933 prescriptions. The estimated wasted volume due to residual volume was 41,394.47 mL. The top ten medications accounted for 51.72% of prescriptions and 48.18% of the wasted financial value. The overall hospital wastage rate was approximately 1.16%. Syringe dead space, frequency of medication administration, and cost per millilitre were identified as the main contributors to medication wastage.

Conclusion

Syringe dead space and residual volume constitute a measurable and avoidable source of medication loss, with relevant economic implications. These findings can inform procurement strategies, waste reduction interventions, and public health policies aimed at optimising healthcare resource use.

1. Introduction

Medication wastage is a frequent topic discussed in healthcare literature [1, 2, 3, 4]. Reflecting its persistent relevance, recent studies continue to quantify the clinical and economic burden of medication wastage across diverse health systems [5, 6]. Many factors can contribute to this problem, including issues related to medication preparation and administration, such as prescription change or interruption after the medication preparation, and mistakes in preparation rendering them unusable [7, 8, 9]. Other factors are related to improper handling of medication vials, such as contamination and breakage [7, 10]. Additionally, issues in the distribution chain and inadequate inventory control can result in the presence of expired medication, playing a significant role in this context [11].

The dead space (DS) in a syringe is a common topic in vaccine administration [12, 13, 14, 15]. This presents a technical limitation that prevents the complete expulsion of the agent from the syringe during administration (Figure 1), resulting in a residual volume $\left(R_{VOL}\right)$ [16, 17]. A study conducted in Brazil estimated that 67 million doses of vaccine were wasted during the COVID‐19 vaccination campaign, despite using high‐quality syringe supplies with the lowest available DS in the country, resulting in a wastage rate of approximately 11.5% [18]. Another study conducted at Uji‐Tokushukai Medical Centre, Japan, pointed out that due to the DS, the 195 vials of the Pfizer COVID‐19 vaccine, intended to vaccinate 1242 employees according to the manufacturer's information, yielded only 975 doses (78.50% of the planned doses), highlighting that syringes with high dead space can influence vaccine dose wastage [19].

Figure 1.

Illustrative scheme of a syringe. The retention plugin is represented in black. The cannon barrel and the needle are represented in grey. After administering the medication, as there is no mechanism that promotes the complete expulsion of the agent, a liquid represented in grey remains inside. This is known as dead space (DS), and the liquid remaining inside is called residual volume ($R_{\mathit{VOL}})$.

Despite the high rate of waste, the DS volume is rigorously regulated and controlled. The International Organisation for Standardisation 7886‐1 (ISO 7886‐1), adopted by the Brazilian Association of Technical Standards (ABNT), specifies the requirements to verify the sterile hypodermic syringe made with plastic or other materials intended for aspiration and injection of fluids [20]. According to ISO 7886‐1, a syringe with a volume equal to or lower than 5 mL can have a maximum DS of 0.07 mL [21].

In this context, this study aims to investigate the economic impact of DS in the administration of medication in a Brazilian Teaching Hospital, focusing on unexplored factors in medication wastage. In addition to quantifying the $R_{\mathit{VOL}}$ of the syringes available in the Hospital, identify the medications with the highest wastage, as well as to estimate a wastage rate.

2. Methods

2.1. Study Location

The study was conducted in the Hospital de Clínicas da Universidade Federal do Triângulo Mineiro, located in the municipality of Uberaba, Minas Gerais, Brazil. HC‐UFTM is a Teaching Hospital and the main healthcare centre in the Health Macroregion of Triângulo Sul (HMTS), which comprises 27 municipalities divided into three Health Microregions: Araxá, Frutal and Uberaba (Figure 2) [22]. The data of the Brazilian Institute of Geographic and Statistics (IBGE) for the Federal Court of Auditors (TCU) indicate a resident population of 806,172 in the HMTS in 2021, which corresponds to 0.38% of the Brazilian population [23].

Figure 2.

Location map of the study area. (A) represents the map of Brazil with emphasis on the state of Minas Gerais. (B) represents the map of Minas Gerais with emphasis on the three Health Microregions: Frutal, Uberaba, and Araxá (from left to right), which compose the Health Macroregion of Triângulo Sul (HMTS). (C) shows the geographic boundaries of the 27 municipalities within HMTS, with emphasis on Uberaba, the municipality where the Hospital de Clínicas da Universidade Federal do Triângulo Mineiro (HC‐UFTM), the main hospital of the HMTS, is located.

2.2. Selection of Studied Medications

To select the medication under study, prescription data for medications at HC‐UFTM in 2022 were collected. This data was obtained from the Information Systems and Data Intelligence Unit at HC‐UFTM. Only medications administered by injection (subcutaneous, intramuscular, or intravenous) that required a syringe for administration were included in this study. Medications that did not meet these criteria were excluded. Prescription details (medication name, route of administration, number of prescriptions, and particular details) were tabulated in Microsoft Excel version 2402.

2.3. Price and Volume of Studied Medications

Data from the Pharmaceutical Supply and Logistics Sector of HC‐UFTM was obtained in order to calculate the cost per millilitre of each medication ($C_m$) studied. First, the total volume of each individual medication requested by HC‐UFTM and their corresponding purchase value were obtained. Then, the corresponding purchase value of each medication was divided by its total requested volume to calculate the $C_m$, as illustrated in Equation 1.

$$C_{\mathit{m}}=\frac{\mathrm{Total}\mathrm{purchase}\mathrm{value}}{\mathrm{Total}\mathrm{medication}\mathrm{volume}\mathrm{requested}}$$ (1)

2.4. Syringe Selection Basead on Prescription

Calculating medication wastage required determining the appropriate syringe size for each application, considering that the syringe size can vary depending on the prescribed volume. Based on the prescription list, two authors (J.C.C and D.R.T) with extensive knowledge in medication preparation independently analysed the data and determined the appropriate syringe size based on the HC‐UFTM prescription preparation guideline. Subsequently, two authors (C.S.D and C.J.F.O) analysed the selected sizes. In case of disagreement, the hospital's technical guidelines are consulted again, and the calculation is performed to determine the optimal syringe option.

2.5. Calculation of Residual Volume of Syringes

The syringes available at HC‐UFTM were obtained from the Pharmaceutical Supply and Logistics Sector. $R_{\mathit{VOL}}$ was calculated in the Immunology Laboratory and Bioinformatics of UFTM, utilising an analytical balance ATY224 (Shimadzu, Japan) and distilled water, following the steps:

• 1.The syringes were removed from the packaging and weighed empty, obtaining the initial weight ($I_W$);
• 2.They were then filled with distilled water up to their maximum graduation;
• 3.A medication administration was simulated by moving the syringe plunger to its limit; due to DS, a quantity of liquid remains inside the syringe, referred to as $R_{\mathit{VOL}}$;
• 4.After the simulation, the syringe was weighed again, obtaining the final weight ($F_W$);
• 5.The difference between the $F_W$ and the $I_W$ was calculated, and considering that the density of distilled water is close to one gram per cubic centimetre, the equivalence between mass and volume was adopted, thus obtaining $R_{\mathit{VOL}}$.
• 6.The measurement process was repeated five times for each syringe, and the mean and standard deviation were calculated. This approach was adopted to ensure a more robust and reliable analysis, enabling the obtainment of representative average results and the evaluation of consistency or variation in the data collected during the repetitions of the process for each syringe in question.

2.6. Calculation of Wasted Volume Per Medication

Having the $R_{\mathit{VOL}}$ of the syringe commonly used in the medication administration, as well as the number of times the medication was prescribed, the total volume of waste for each medication was calculated using Equation 2.

$$W_{\mathit{VOL}}=R_{\mathit{VOL}}·n_m$$ (2)

Where,

$W_{\mathit{VOL}}$ = Total volume of wasted per medication;

$R_{\mathit{VOL}}$ = Residual volume of the syringe indicated for medication administration;

$n_m$ = Number of times the medication was prescribed.

2.7. Calculation of the Wasted Value Per Medication

Considering the $C_m$ and $W_{\mathit{VOL}}$, it was possible to calculate the wasted value for each medication individually through Equation 3.

$$W_m=C_m·W_{\mathit{VOL}}$$ (3)

Where,

$W_m$ = Wasted value for each medication individually;

$C_m$ = Average cost per millilitre of the medication;

$W_{\mathit{VOL}}$ = Total volume of wasted per medication.

2.8. Calculation of Hospital Wastage

From the sum of all $W_m$, the total waste in HC‐UFTM was obtained, as demonstrated in Equation 4.

$$H_{\mathit{wm}}=\sum _1^n{W}_{m_n}$$ (4)

Where,

$W_m$ = Wasted value for each medication individually;

$H_{\mathit{wm}}$ = Wasted value of the hospital, considering all wasted medications.

2.9. Calculation of the Wastage Rate

The wastage rate ($W_{\mathrm{rate}}$) was calculated considering $H_{\mathit{wm}}$ in relation to the total cost ($T_{\mathrm{cost}})$ spent on obtaining the medications. This rate directly reflects the operational loss due to medication administration, as demonstrated in Equation 5.

$$W_{\mathrm{rate}}=\frac{H_{\mathit{wm}}}{T_{\mathrm{cost}}}$$ (5)

Where,

$W_{\mathrm{rate}}$ = Wastage rate reflecting the wasted value due to $R_{\mathit{VOL}}$in relation to the value spent on purchasing the studied medications;

$H_{\mathit{wm}}$ = Wasted value of the hospital, considering all wasted medications;

$T_{\mathit{cost}}$ = Total cost spent on purchasing the studied medications.

3. Results

3.1. Residual Volume of the Syringes

A total of seven syringes were subjected to the calculation of the $R_{\mathit{VOL}}$. Of these, only one specimen was available for the 1 millilitre (mL), 3 mL, 10 mL, and 20 mL syringes, while there were three specimens of the 5 mL syringe. The examined syringes, along with the mean residual volume and their respective standard deviations in millilitres, are presented in Table 1.

Table 1.

Mean residual volume and standard deviation in syringes available at HC‐UFTM.

Syringe	Size	Manufacturer	Mean ± SD (mL)
Medix Bico Luer Slip	1 mL	Taihu County, China	0.0319 ± 0.0018
Injex Bico Luer Lock	3 mL	Ourinhos, São Paulo, Brazil	0.0447 ± 0.0013
Descarpack Bico Luer Slip	5 mL	Gurgaon, India	0.0550 ± 0.0021
Saldanha Rodrigues Bico Luer Slip	5 mL	Manaus, Amazonas, Brazil	0.0523 ± 0.0017
Descarpack Bico Luer Lock	5 mL	Gurgaon, India	0.0566 ± 0.0004
ABL Bico Luer Lock	10 mL	Itajaí, Santa Catarina, Brazil	0.0629 ± 0.0013
Saldanha Rodrigues Bico Luer Lock	20 mL	Manaus, Amazonas, Brazil	0.0622 ± 0.0003

Abbreviations: mL, millilitre; SD, Standard deviation.

3.2. Wasted Volume of Medications

The total of 120 medications met the inclusion criteria in the study and were subjected to investigation. During the year 2022, these medications were requested by HC‐UFTM on 693,933 occasions, and the total estimated wasted volume due to the $R_{\mathit{VOL}}$ was 41,394.47 mL. The top ten most requested medications accounted for 51.72% of the total requests, demonstrating a wide variability in the number of requests, with a maximum of 52,105, a minimum of 11, a mean of 5782.78, a standard deviation of 10,288.14, and a coefficient of variation of 177.91%. Additionally, the top ten medications with the highest wasted volume are those that had the highest number of requests, as illustrated in Table 2.

Table 2.

Most prescribed medications with the highest volume wasted in 2022 at HC‐UFTM.

Medication	Number of prescriptions	${\mathit{W}}_{\mathit{VOL}}$ (mL)a	Class
Norepinephrine	52,105	3282.61	Adrenergic agent
Oxacillin	38,790	2412.73	Antibiotic
Fentanyl	36,824	2283.08	Opioid analgesic
Ondansetron	36,265	2284.69	Antiemetic
Omeprazole	35,920	2262.96	Proton pump inhibitor
Metoclopramide	34,594	1971.85	Antiemetic and prokinetic
Furosemide	34,429	1962.45	Loop diuretic
Midazolam	31,025	1954.57	Benzodiazepine
Ceftriaxone	30,508	1922.00	Antibiotic
Tramadol	28,493	1624.10	Opioid analgesic

Abbreviations: mL, millilitre; ${\mathit{W}}_{\mathit{VOL}}$, total volume wasted per medication.

^a The table is sorted in descending order based on the volume wasted for each medication.

3.3. Hospital Wastage

In the year 2022, the total estimated wasted value was R$71,458.47. The top ten medications with the highest budgetary impact accounted for 48.18% of the total wasted value (Table 3). A wide variability in wasted value was also found, with a maximum of R$7625.03, a minimum of R$1.09, a mean of R$595.48, a standard deviation of R$1108.74, and a coefficient of variation of 186.19%.

Table 3.

Medications with the highest value wasted in 2022 at HC‐UFTM.

Medication	n	${\mathit{W}}_{\mathit{VOL}}$ (mL)	${\mathit{C}}_{\mathit{m}}$ (R$)	${\mathit{W}}_{\mathit{m}}$ (R$)a	Class
Octreotide	504	28.54	267.14	7625.03	Somatostatin analogue
Norepinephrine	52,105	3282.61	2.02	6625.47	Adrenergic agent
Omeprazole	35,920	2262.96	2.10	4747.38	Proton pump inhibitor
Midazolam	31,025	1954.57	1.57	3063.18	Benzodiazepine
Sodium Heparin	9028	514.59	4.98	2562.17	Anticoagulant
Cisatracurium besilate	6616	416.80	5.58	2324.39	Neuromuscular blocker
Ondansetron	36,265	2284.69	0.92	2102.56	Antiemetic
Rocuronium bromide	5668	357.08	5.75	2052.38	Neuromuscular blocker
Epinephrine	18,130	1033.41	1.63	1684.46	Adrenergic agent
Imipenem + Cilastatin	14,071	886.47	1.85	1643.50	Antibiotic

Abbreviations: ${\mathit{C}}_{\mathit{m}}$, cost per millilitre of each medication; n, number of prescriptions; ${\mathit{W}}_{\mathit{VOL}}$, total volume wasted per medication; ${\mathit{W}}_{\mathit{m}}$, wasted value for each medication.

^a The table is sorted in descending order based on the value wasted for each medication.

The total amount spent on purchasing the studied medications in 2022 was R$6,167,429.56. Based on the estimated wasted value of R$71,458.47, this implies that the wastage rate, or the operational loss rate, is approximately 1.16%.

4. Discussion

The results of this study highlight the issue of medication wastage due to residual volume present in syringes, a problem widely discussed in the field of vaccine administration and less explored in the context of medication administration. The data indicate that HC‐UFTM, the main tertiary hospital in the South Triangle Health Macroregion, had a wastage of R$71,458.47 in 2022. Considering that this macroregion accounts for approximately 0.38% of the Brazilian population, a simple proportional extrapolation would place the corresponding national wastage in the order of R$18.8 million per year. This estimate must, however, be interpreted with caution, as it assumes a comparable case‐mix, prescription volume, and syringe portfolio across institutions. The acquisition of medical supplies in bulk through centralised public bidding, which is structural to the Brazilian public health system [24, 25, 26], makes a low variability in syringe dead‐space plausibly widespread; nevertheless, single‐centre extrapolations of this kind, although previously reported in the Brazilian setting [27], require confirmation through multicentre data before the true national magnitude can be reliably established [5].

The shortage of different syringes with the same graduation, found in this study, occurs due to the hospital material acquisition process, which is carried out through bidding processes and involves bulk purchasing [26]. This results in a low variability of syringes and often hinders the development of strategies aimed at reducing medication wastage, such as prioritising the use of syringes with lower residual volume when administering high‐cost medications per millilitre [25].

Indeed, the results underscore the need to implement models that enhance the process of acquiring medical supplies, such as syringes, in the public sector. By employing cost‐effectiveness models, that is, evaluating the individual price of syringes in relation to their residual volume and predicting the impact of price variation and the quantity of wasted medications, it is possible to determine whether acquiring more expensive equipment with lower residual volume can reduce the total cost of operation in healthcare delivery [24].

Important factors identified in this study expose three elements that can influence the economic impact of medication wastage. The DS of the syringe used to administer the medication, as the higher the DS, the greater the wasted $R_{\mathit{VOL}}$. The frequency with which a medication is requested, as the more frequently it is administered, the greater the total $R_{\mathit{VOL}}$ generated. The $C_m$, as the higher this cost, the greater the value wasted per millilitre when compared to medications with low cost. Equation 6 illustrates this relationship.

$$E_{\mathit{mw}}\propto R_{\mathit{VOL}},n_m,C_m$$ (6)

Where,

$E_{\mathit{mw}}$ = Economic impact of medication wastage;

$R_{\mathit{VOL}}$ = Residual volume;

$n_m$ = Number of times the medication is administered;

$C_m$ = Average cost per millilitre of the medication;

$\propto$ = Indicates that $E_{\mathit{mw}}$ has a strictly increasing value in relation to the factors presented.

These factors are easily visualised in the study. Octreotide, a somatostatin analogue used in the treatment of acromegaly and neuroendocrine tumours [28], presents itself as the medication with the highest $C_m$ (R$ 267,14) and the highest individual $W_m$ (R$ 7625.03 representing 10.67% of the wasted value), but with few requests (0.07% of requests). This highlights that medications with high cost should undergo greater intervention due to their high associated value and low quantity of existing requests, which makes intervention easier [29, 30, 31].

Regarding the number of times the medication is administered, two medications stand out: Norepinephrine, with 52,105 requests, $C_m$ of R$2,02 (58th position of $C_m$), anking second in individual $W_m$ (R$6625.47 representing 9.27% of the wasted value), and Ondansetron, with 36,265 requests, $C_m$ of R$0,92 (93rd position of $C_m$), ranking seventh in individual $W_m$ (R$2,102.56 representing 2.94% of the wasted value). They are among the medications with the highest$W_m$, even though they have a much lower $C_m$ than Octreotide, exposing that not only high‐cost medications can directly impact the budget, but also the frequency with which they are used [30].

Another important characteristic is the DS of the syringe commonly used in medication administration. Fentanyl was the fourth most requested medication, with 36,824 requests, while Ondansetron was the fifth, with 36,265. However, when analysing the wasted volume, the positions are reversed, with Ondansetron in fourth place, with 2284.69 mL, and Fentanyl in fifth, with 2283.08 mL. This occurs due to the nature of medication administration itself, in which Ondansetron is administered in syringes with higher graduation and higher DS, resulting in a higher $R_{\mathit{VOL}}$ when compared to Fentanyl. This factor reinforces the need to consider the $R_{\mathit{VOL}}$ factor for waste reduction.

These findings translate into a set of concrete and complementary measures. First, procurement decisions for injectable medications should move beyond unit price alone and incorporate residual volume as an explicit criterion, for instance, through cost‐effectiveness or multicriteria models that weigh the higher acquisition price of low‐dead‐space devices against the volume of drug they spare [25, 32]. This is particularly relevant for medications with a high cost per millilitre, such as octreotide, for which low‐dead‐space and ready‐to‐administer (prefilled) presentations have been shown to reduce wastage and to generate net savings for the institution [32, 33]. Second, for high‐cost, low‐frequency injectables, centralised preparation together with dose‐ or vial‐sharing within the pharmacy can pool residual volumes that would otherwise be discarded at the bedside [34, 35]. Third, standardised pharmacist verification of prescriptions immediately before preparation reduces the waste that arises when therapies are changed or discontinued after a dose has already been prepared [36]. Finally, the routine auditing of medication wastage as an institutional performance indicator — feasible within the clinical pharmacy services already present in most tertiary hospitals — would allow institutions to monitor losses over time and to direct their interventions to where the financial impact is greatest [5]. Beyond their economic rationale, these measures also align with medication safety, since prefilled and ready‐to‐administer presentations reduce preparation errors and the associated preventable adverse drug events, and with environmental sustainability, by curbing avoidable pharmaceutical waste [6, 33].

In conclusion, this study highlights the significant economic impact of DS in the administration of medication, with a wastage rate of 1.16% due to unexplored factors in medication wastage. In fact, three main aspects were demonstrated when considering medication wastage in relation to DS: the residual volume of the syringe, the frequency of medication administration within a certain period of time, and the average cost per millilitre of the medication administered. By making residual volume an explicit criterion in the procurement, preparation, and auditing of injectable medications, hospitals and health authorities can convert these currently underexplored losses into a tractable target for cost containment and for more sustainable use of healthcare resources.

Author Contributions

Yago Marcos Pessoa‐Gonçalves: conceptualisation, searches and screening, methodology, data extraction, formal analysis, writing – original draft. Victor Hugo Palhares Flávio‐Reis: conceptualisation, searches and screening, methodology, data extraction, formal analysis. Jacqueline Cristiane Costa and Daniela Ramos Tostes: methodology, data extraction. Chamberttan Souza Desidério: conceptualisation, methodology, writing – review and editing. Carlo José Freire de Oliveira: conceptualisation, methodology, writing – review and editing, supervision.

Ethics Statement

The data acquisition process followed the guidelines established by the Brazilian System of Ethical Evaluation in Research with Human Beings (CEP/CONEP) and received approval from the ethics committee of HC‐UFTM, under protocol CAAE 67898823.4.0000.8667.

Conflicts of Interest

The authors declare no conflicts of interest.

Pessoa‐Gonçalves Y. M., Flávio‐Reis V. H. P., Costa J. C., et al., “Unexplored factors in medication wastage: investigating economic impact in a Brazilian Teaching Hospital,” Journal of Evaluation in Clinical Practice 32 (2026): e70530. 10.1111/jep.70530.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.