The use of high dose topical capsaicin in the management of peripheral neuropathy: narrative review and local experience

Abstract

Capsaicin, derived from the chilli pepper plant, is available in high concentration (8%) patches to provide topical therapy for neuropathic pain. Its analgesic effects relate to defunctionalisation and nerve terminal retraction of predominantly C fibres in the dermis and epidermis. Systematic reviews and meta-analysis support its use for the management of post-herpetic neuralgia and HIV neuropathy with some evidence for use in painful peripheral diabetic neuropathy. The article concludes with advice on the practicalities of running a topical 8% capsaicin clinic for peripheral neuropathic pain.

Introduction

Capsaicin is a derivative of the genus plant Capsicum, being the primary pungent agent of Capsicum fruits from the chilli pepper plant that originate from the South America. The first recorded example of its use for the treatment of pain dates back to 4000 BC. Following introduction to Europe by Christopher Columbus in the 1400s, it was used for both its gastronomic and healing characteristics.¹ Capsaicin has been reported as a treatment for itching, headaches and skin conditions since the mid-19th century. In 1846, its pure form was isolated by Thresh, and Nelson determined its chemical structure in 1919.² Topical capsaicin leads to skin irritation and a burning sensation; therefore, its use in managing pain could be considered as counter-intuitive. However, it has been shown to lead to pain reduction in chronic pain conditions, including neuropathic pain. It is available in a number of formulations, including 0.025% to 0.075% creams, lotions and low and high concentration patches. Lower dose formulations have failed to demonstrate analgesic effect in clinical trials, and as this can lead to local skin irritation, poor compliance was common.³ To avoid repeated application of low dose formulations, a high dose (8%) topical capsaicin patch was developed (current trade name Qutenza^®; Grunenthal Ltd, Germany). This allows for rapid skin delivery with less frequent applications, thus improving tolerability. 8% capsaicin patches were approved in 2009 for the treatment of non-diabetic peripheral neuropathic pain in the European Union (EU), with extension of its licencing in 2015 to include patients with diabetes who had neuropathic pain.^4,5 Neuropathic pain is defined as the pain caused by a lesion or disease of the somatosensory nervous system,⁶ and common conditions associated with its development include diabetes, post-herpetic neuralgia, stroke, HIV and peripheral nerve injury.⁷ Patients can experience a range of symptoms, including significant pain – that is, characteristically described as burning, shooting, tingling and freezing sensations – of moderate to severe intensity and present for many years.⁷ Individuals who experience pain with neuropathic characteristics have associated impaired sleep and quality of life, increased anxiety and depression and increased utilisation of healthcare facilities.⁸ Inadequate response in patients with neuropathic pain to systemic drug treatments represents a clinical need,⁹ either from a lack of efficacy or intolerable side-effect profiles. Here, topical treatments such as 8% capsaicin patches offer potential therapeutic opportunity. In this narrative review, we aim to discuss the pharmacology of capsaicin, explore evidence of its efficacy in peripheral neuropathic pain and describe the practical application of this therapy in a clinical setting.

Pharmacology

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is a naturally occurring alkaloid that is a highly selective agonist for the trans-membrane receptor–ion channel complex TRPV1 (transient receptor potential vanilloid 1).¹⁰ TRPV1 receptors are expressed mainly on C and some Aδ nociceptive sensory nerves and are activated by a combination of heat (>43°C), protons, endogenous and exogenous agonists. They are non-selective cation channels, with a high permeability to calcium.¹¹ Brief exposure to these stimulants leads to transient opening of TRPV1 receptors and subsequent depolarisation through calcium and sodium ion influx (at a ratio of 8:1) into nerves. This can be experienced as a warming, burning, stinging or itching sensation⁵ which occurs alongside a neurogenic inflammatory picture due to localised release of neuropeptides from the peripheral nerve terminals, causing redness, swelling and further pain.^12,13 In contrast, high concentration or repeated capsaicin administration leads to pain relief through a process termed ‘defunctionalisation’¹⁴ – a consequence of more persistent biochemical effects. The calcium:sodium ion influx ratio alters to 25:1, leading to a large flow of calcium into nerve fibres. Voltage-gated ion channels then become inactivated, with reduced ability to form action potentials. TRPV1 receptors are also located on intracellular organelles that are stimulated by capsaicin and lead to mobilisation of calcium from internal cellular stores. These sustained levels of intracellular calcium then activate calcium dependent enzymes which induce cytoskeletal changes and drive accompanying chloride shifts that promote osmotic swelling of nerves. Microtubule depolymerisation can interrupt fast axonal transport. Independent of TRPV1 binding, capsaicin can also lead to mitochondrial respiration disruption. These mechanisms impair nociceptor function and contribute to nerve terminal retraction, with loss of terminals in the epidermis and dermis.⁵ Together these processes lead to decreased C fibre input to the central nervous system and a reduction in pain.

Capsaicin is a lipophilic, non-water soluble compound that resists absorption into blood and systemic uptake. However, as only small amounts of capsaicin are metabolised in the skin, its removal from the dermis is by slow diffusion into blood vessels and transportation to the liver to undergo hepatic metabolism.¹⁵ Topical capsaicin will therefore exert its effects close to its site of application, as it remains unchanged in the dermis until slow systemic uptake and hepatic metabolism. The 280-cm² capsaicin 8% patch contains 179 mg of capsaicin (640 µg/cm²).¹⁶ Capsaicin is released in a linear fashion from its patch during application, with approximately 1% being absorbed into epidermal and dermal layers of skin from an 8% patch over 60 minutes.¹⁶ Unlike transdermal drug delivery systems, the ambient temperature and application time do not influence bioavailability.¹⁷ Initial efficacy and safety studies recommend 30 minutes application for thick, hairless skin (such as palm/soles of feet) and 60 minutes for thin or hairy skin,¹⁶ and this is supported by data showing sufficient bioavailability of capsaicin in both skin types at 30 minutes after application.¹⁷ Side-effect profiles tend to be localised pain, erythema, oedema and pruritus that are transient and resolve with patch removal. Rarely, a transient increase in blood pressure (<8 mm Hg) has been observed in clinical trials as a systemic effect, and therefore, blood pressure monitoring during application is recommended.¹⁶

Evidence regarding the use of high concentration topical capsaicin in chronic neuropathic pain

The best evidence to date regarding the use of high dose topical capsaicin in chronic neuropathic pain comes from the Derry et al.⁴ Cochrane Review published in 2017. This evaluated all randomised, double blind trials in adults published between January 2012 and June 2016 that compared high concentration topical capsaicin with placebo or other active treatment for neuropathic pain, where there was a minimum of 10 participants per treatment arm. Eight studies were considered that included a total of 2488 participants. Two studies compared 8% capsaicin patches with placebo and the remaining six studies used 0.04% topical capsaicin as an ‘active’ placebo to help blinding of participants. Four studies (1272 participants) considered individuals with post-herpetic neuralgia, two with HIV neuropathy (801 participants), one with peripheral diabetic neuropathy (369 participants) and one with persistent pain after inguinal herniorrhaphy (45 participants). The authors concluded that a single application of 8% capsaicin for between 30 and 90 minutes gave some people with chronic pain arising from post-herpetic neuralgia or HIV neuropathy, up to 12 weeks significant pain relief. They calculated a number needed to treat between 6 and 9 over this timeframe. The authors’ evaluated measures of pain intensity reduction as less reliable in the studies compared to patient responses of perceived pain improvement. However, results for average pain intensity reduction of ‘at least 50%’ or ‘at least 30%’ over the 12-week study period supported pain improvement data. Patients with peripheral diabetic neuropathy showed similar responses to post-herpetic neuralgia and HIV neuropathy for the outcomes of ‘at least 30%’ pain intensity reduction and reporting outcomes of ‘much improved’ or ‘very much improved’ pain. However, there was little difference between capsaicin and placebo groups for ‘at least 50%’ pain reduction in those with peripheral diabetic neuropathy. The authors concluded there were insufficient data to draw conclusions about the use of 8% capsaicin in diabetic neuropathy. This was also true for persistent pain after inguinal herniorrhaphy. Adverse event recording highlighted an increase in localised skin reactions such as erythema and burning in the 8% capsaicin groups, but these resolved quickly and there were no differences in serious adverse events between placebo and 8% capsaicin groups. The authors noted that it was not clear how repeated applications of capsaicin 8% affected outcomes and adverse events.

This is in agreement with evidence regarding topical 8% capsaicin efficacy in a more generalised systematic review and meta-analysis by Finnerup et al.,⁹ of randomised double blind studies of pharmacotherapy for neuropathic pain considering publications between January 1966 and April 2013. This considered a total of seven papers exploring 8% capsaicin use in post-herpetic neuralgia or HIV neuropathy. The Cochrane Review included six of these studies, alongside two that were published in 2014 after Finnerup et al. had completed their literature search. The additional paper included by Finnerup et al.⁴ was not included in the Cochrane Review due to only having a 4-week study period. Overall, the quality of evidence was evaluated to be high, with studies showing a sustained efficacy of 8% capsaicin therapy and calculated the number needed to treat as 10.6. To place this number needed to treat in context, first-line therapies such as tricyclic antidepressants, serotonin–noradrenaline reuptake inhibitors, pregabalin and gabapentin were calculated to have values of 3.6, 6.4, 7.7 and 7.2, respectively. The authors felt the results for 8% capsaicin were susceptible to publication bias and gave a weak recommendation for capsaicin to be used as a second-line therapy for neuropathic pain.

The Derry et al. work is the most up to date systematic review; however, it only collected publications up until June 2016. We performed a literature search to review more recent evidence, replicating the Derry et al.⁴ MEDLINE search strategy for clinical trials of topical 8% capsaicin published between June 2016 and November 2019. The search listed 97 articles that underwent title and abstract reviews, leading to eight publications identified as clinical trials for topical 8% capsaicin in neuropathic pain conditions. Of these, one publication was a randomised, double blind, placebo-controlled trial by Simpson et al.¹⁸ Details regarding seven of the publications are summarised in Table 1.^18–24 One paper by Filipczak-Bryniarska et al.²⁵ has not been included, as it reports a single-centre experience of 8% capsaicin therapy in 18 patients with oxaliplatin-induced neuropathy. The Simpson et al.¹⁸ publication gives further evidence to the efficacy of 8% capsaicin in the management of painful diabetic peripheral neuropathy and would be a useful addition to further systematic review and meta-analysis. Four of the publications address one of the questions raised by Derry et al.⁴ regarding safety of repeated applications. They mimic, or in two instances collect data from, clinical practice where repeated applications are potentially necessary.^21–24 These publications highlight important data about the relative tolerability of repeated therapy and the lack of neuronal damage from repeated applications that could cause neurological deficits that impact on an individuals’ function. In addition, a national, longitudinal, post-marketing surveillance study of 684 non-diabetic patients with peripheral neuropathy demonstrated treatment success in 21.8% of participants in the 6 months following the individuals last application (of which they could have had between 1 and 5 topical 8% capsaicin treatments) based on a >30% numerical pain rating scale reduction and improvements in patients global impression of change scores which support the studies examining repeated use.²⁶

Table 1.

Studies identified in updated literature search for clinical studies on the use of topical 8% capsaicin in neuropathic pain.

Study year and first author	Trial type	Total participant numbers (allocated to 8% capsaicin arm)	Primary outcome and results	Secondary outcomes and results	Other points of interest	References
2016 Haanpää	Randomised, open label, multicentre, non-inferiority study over 8 weeks Topical 8% capsaicin (once) versus optimal pregabalin dose	559 (282)	>30% mean pain relief measured by NPRS between baseline and week 8 55.7% capsaicin group versus 54.5% pregabalin group	No difference between groups for optimal therapeutic effect. Time to onset of pain relief was shorter for capsaicin group (7.5 days versus 36 days for pregabalin)	Significant difference in treatment satisfaction favouring capsaicin (fewer withdrawals, more willing to continue treatment, mean treatment satisfaction scores)	19
2018 Cruccu	Randomised, open label, multicentre, study over 8 weeks Topical 8% capsaicin (once) versus optimal pregabalin dose	488 (253)	None (population were from Haanpää study)	Area DMA: −39.5 cm2 DLSM favouring capsaicin Change in intensity DMA: −0.67 DLSM favouring capsaicin Complete resolution DMA: 24.1% capsaicin versus 12.3% pregabalin		20
2017 Galvez	Open label single-arm safety study of repeat treatment non-diabetic peripheral neuropathy over 52 weeks Topical 8% capsaicin	306	Adverse events: 82.4% reported treatment-related adverse events, the most common with application site pain or erythema Sensory function measured with bedside tests: variable sensory changes with four patients experiencing complete loss of function Average pain reduction on NPRS at 12 months from baseline: 4.7 from 6.6			21
2017 Mankowski	Open label non-interventional study non-diabetic peripheral neuropathy over 52 weeks Topical 8% capsaicin part of clinical practice	412	Average daily NPRS score 2 and 8 weeks: 26.6% reduction from baseline Median time between first and second treatments: 191 days	EQ5D: increase of 0.199 utilisation at week 2 and maintained to week 52 PGIC: majority experienced improvement in health status	Well tolerated: 11.2% reported adverse events most frequently pain, erythema and pruritus at application site	22
2017 Simpson	Randomised, double blinded, placebo-controlled trial in painful peripheral diabetic neuropathy Topical 8% capsaicin versus placebo	369 (186)	Change in NPRS from baseline to average of 2–8 weeks: −27.4% capsaicin versus −20.9% placebo	Time to treatment response: 19 days capsaicin versus 72 days placebo Sleep interference scores: greater mean reduction with capsaicin compared with placebo	Similar adverse events except application site reactions were higher with capsaicin	18
2016 Vinik	Randomised 52-week open label safety study of repeat application Topical 8% capsaicin for 30-or 60-minute application and SOC versus SOC	468 (30 minutes: 156) and (60 minutes: 157)	Potential deleterious functional effects of capsaicin treatment on peripheral nerves measured by Norfolk QOL-DN scale changes between baseline and 52 weeks: no difference in total scores between groups	No worsening of sensory perception between groups for neurological examination or reflexes		23
2018 Hansson	Three non-interventional observational studies in clinical practice Topical 8% capsaicin first and repeat treatment	382 first treatment and 181 repeat treatment	Mean change in pain intensity on NPRS from baseline to mean between 2 and 8 weeks: −1.05 at first treatment and −0.75 at repeat treatment	>30% reduction in NPRS from baseline to mean between 2 and 8 weeks: 28% at first treatment and 31% at repeat treatment	Overall improvement in quality of life measures 57% after first treatment and 71% after second treatment were willing to undergo further applications	24

NPRS: numerical pain rating scale, DMA: dynamic mechanical allodynia, DLSM: difference in least square means, EQ5D: EuroQual 5-dimension 3-level questionnaire, PGIC: patient global impression of change, SOC: standard of care; QOL-DN: quality of life questionnaire–diabetic neuropathy.

Finally, the two publications from the ELEVATE study compare 8% capsaicin with pregabalin, a first-line neuropathic pain treatment. They demonstrate non-inferiority between treatments and notably improved satisfaction of treatment with capsaicin.^19,20 While the Cochrane Review by Derry et al. is the best summary of evidence to date, new studies further support the use of 8% capsaicin patches in peripheral neuropathic pain management through its ability to reduce pain and being well tolerated with rare adverse events except for application associated transient pain, erythema and pruritus. The evidence base would, however, benefit from further robust randomised controlled trials using active placebos, with endpoints evaluating not only average pain scores but also pain reduction and quality of life measures. These should encompass neuropathic pain conditions outlined above and also consideration should be given to target other modalities of pain, including post-surgical pain.

Delivering a capsaicin service

Identifying patients who may benefit from high dose capsaicin therapy

The Finnerup et al.⁹ guidelines recommend topical capsaicin as a second-line therapy for neuropathic pain and the Derry et al.⁴ Cochrane Review concluded that it may benefit patients with post-herpetic neuralgia, HIV neuropathy and painful diabetic peripheral neuropathy. In addition, it is a useful treatment for individuals where systemic therapies for neuropathic pain can be problematic, such as the elderly where side effects are poorly tolerated or individuals with polypharmacy at risk of drug interactions. However, one needs to determine which patients are potentially suitable for capsaicin therapy, as only four 280 cm² patches can be used at any each session.¹⁶ Therefore, individuals where pain is isolated to a specific anatomical area or two to three small areas should be considered, with care taken to consider areas of the body that have a large surface area. For example, from our experience, the application of capsaicin 8% patches to dorsal and plantar aspects of both feet can often require up to four patches. The summary of product characteristics does not recommend the use of capsaicin for facial pain. We are aware of published case series regarding its use for facial pain, especially from post-herpetic neuralgia. Facial application would need to ensure that aerosol particles of capsaicin do not enter patients’ eyes; therefore eye shields or goggles would be required. However, its use in these circumstances is outside our clinical expertise.

Pre-treatment discussions

It is important to ensure pre-treatment counselling regarding potential benefits – what to expect during therapy and its potential outcome. This may require reassurance about the treatment, particularly as it can cause an increase in pain intensity during patch application and it is not guaranteed to lead to a significant reduction in pain. Patients can be reassured that 8% capsaicin therapy has a low risk of drug–drug interactions and as it has transient, low levels of systemic absorption, and dose adjustment is not required in renal or hepatic impairment.²⁷ We have found that patient information leaflets can be extremely helpful in reinforcing clinic discussions.

The treatment setting

This can vary between different hospital settings; however; any treatment room needs to be well ventilated, as capsaicin particles can disperse in the air leading to inhalation for patients and staff if poorly ventilated rooms. In addition, running water needs to be available in the room, alongside equipment to enable full monitoring of blood pressure, heart rate and oxygen saturations, and resuscitation equipment easily accessible.

Essential equipment for application include the 8% capsaicin patches, a skin-marking pen, transparency pages, nitrile gloves, scissors, cleansing gel (which comes with the manufactured patches), soap and water, washcloths and towels, topical anaesthetic if requested by patient, occlusive dressings, dry gauze pads, 1-inch paper surgical tape, 4-inch gauze wrap, cooling measures, simple oral analgesia, polyethylene medical waste bag for patch and equipment disposal. It is helpful to prepare and have available all of the equipment before beginning the application procedure, as removing gloves during application can lead to capsaicin particles coming in contact with one’s own skin.

If there are several patients receiving 8% capsaicin on a list, it is possible to overlap patient slots to ensure list efficiency if there are available nursing staff and a bay for patient trolleys with monitoring. During the 30- to 60-minute time of the patches application, additional patients can be in the treatment room having their treatment applied. Using a table to chart patch application and the time it should be removed can ensure that the patches are not applied for longer than needed as this can cause discomfort to the patient. This is especially helpful when alternating between individuals with different application times, for example, in feet where the application time is only 30 minutes compared to 60 minutes for thinner skin.

Preprocedure

Patients do not need to be starved before treatment. They require written consent, and this should include a discussion of risks such as increased pain, no effect, erythema, pruritus, rash, burning sensation, allergy and hypertension. Setting expectations early about what they may experience during the application can help individuals tolerate the procedure. It is important to inform the patient that treatment site reactions such as redness or a burning sensation frequently occur and does not correlate with the effectiveness of the treatment. However, it can be helpful to include that some individuals do not feel anything from the treatment, which again does not correlate with treatment effect.

Applying capsaicin patches

The treatment area should be determined by examination, identifying areas of allodynia (pain from a stimulus that does not normally provoke pain) or hyperalgesia (increased pain from a stimulus that normally provokes pain) and any painful regions that extend beyond this.²⁸ Once identified, removing hair from the treatment area is necessary, and it should be cut rather than shaved to prevent accidentally cutting the skin; hence, patients can be advised to do this a couple of days before treatment. The painful area should be marked on the skin using a marker that will not rub off during the procedure. The treatment area can be traced onto a stencil/transparency or directly onto the capsaicin patch, and anatomical markings can be used to ensure that the patch is applied in the correct position. While initial guidance recommended pre-treatment of skin with topical local anaesthetics, published evidence and our local audit data suggest that skin cooling following capsaicin removal is as effective as topical anaesthetics to reduce burning.²⁹

Hands and feet can be particularly difficult to apply patches. In this situation, the capsaicin patch is ideally cut into strips and then applied to the skin. Good adherence to the skin is vital, and it is important to ensure that there are no air bubbles between the patch and the skin, otherwise the capsaicin will not transfer into the skin. This can be aided by making a diagonal cut in the patch release liner to aid in its removal that occurs just before application. Then holding the patch in place, slowly and carefully peel away the release liner with one hand, while simultaneously smoothing the patch onto the skin with the other hand. Other techniques to improve adhesion include cutting the patch into smaller pieces and pulling the skin taut before application. Tips to aid adhesion include applying pressure to the patch during application, using gauze or bandages to wrap the treatment area and asking the patient to lie on the treatment area. Allow the patch to remain in place for 30 minutes for the feet or 60 minutes for any other area.

If the patient develops a burning sensation in the eyes, skin or airway, then remove the patient in the vicinity of the treatment area. Flush eyes or mucous membranes with water. Provide appropriate medical care if shortness of breath develops. Should the patient experience pain from the patch site often distraction can help treatment tolerability. We recommend individuals bring something to occupy themselves during the treatment, such as reading materials. A minimum of blood pressure, heart rate and oxygen saturation observations taken before, during and after treatment are required. In addition, a baseline blood sugar level in diabetics should be performed. Any abnormalities noted on the first set of observations need to be addressed before starting treatment.

Managing treatment associated discomfort

Simple oral analgesia such as paracetamol and ibuprofen provide an effective way of managing any treatment-related discomfort and should be used along with local cooling, if necessary, to treat acute pain during and following the procedure. In our experience, it is best to avoid the use of wet compresses during the capsaicin therapy as moisture can impact on patch adhesion. In general, pain reduces once the 8% capsaicin patch has been removed and the cleansing gel is applied. However, on rare occasions, when the pain does not settle, the use of chilled (not frozen) cool packs wrapped in material to avoid direct contact with the skin can be helpful if applied to the treated area. Although not entirely understood, it is thought that cooling reduces capsaicin-related pain either by possibly antagonising capsaicin activation of TRPV1 receptors or by activating transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8) receptors (another temperature channel on primary sensory neurons), sensitised at 15°C to 30°C.²⁹

Removal and aftercare

Slowly and gently remove the capsaicin patch by rolling it inwards to minimise the risk of aerosolisation of capsaicin. Both used and unused patches, along with all other materials that have been in contact with the treated area, should be disposed of by sealing in a polyethylene medical waste bag and placing in an appropriate medical waste container. The cleansing gel is then liberally applied to the treatment area and left in contact for at least 1 minute. This is then removed with dry gauze, and the area is gently washed with soap and water. It is important to ensure the capsaicin-contaminated water or gel does not contact the surrounding skin.

Patients may experience adverse effects related to local application site reactions, the most common of which include: erythema, pain, pruritus, oedema, swelling and whiteness or patchy areas. Symptoms are generally mild to moderate in severity and resolve spontaneously within 7 days. We find patients benefit from being given an information leaflet regarding their treatment. Our hospital leaflet includes details about the treatment, its side effects, how the treatment is performed, what to expect during the treatment, advice on what to expect following treatment and follow-up plans. Patients can develop a rebound pain, most commonly within the first 24 hours following treatment. We advise that if patients develop redness or burning at home, they can apply covered ice packs to the area only for 20 minutes at a time or apply aloe gel to the area for up to 20 minutes and then wipe off. A rare complication of capsaicin is blistering at the application site. This requires medical attention and patients are given the contact details of where to gain advice and further care especially out of normal working hours. When caring for the treated area, patients are informed that they can shower and wash the area as usual but need to avoid very hot water as this can exacerbate the pain. In addition, we give advice on washing clothes and bed linen soon after treatment as they may contain capsaicin residue. They are also advised that the area treated might be more sensitive in the next few days, so they should continue taking analgesia and this can start to be reduced if and when pain improves. Finally are informed that they may experience pain relief from day 1, but it can take up to 14 days to feel any benefit, and have clear information about their further care and clinic appointments.

Evaluating service outcomes

The efficacy of an 8% capsaicin service can be evaluated through collecting simple data about the treatment and telephone follow-up responses. Our service has administered over 800 treatments of 8% capsaicin since 2011, including repeated applications. We collect data during the treatment, including pain aetiology, pain location and pre-application pain intensity scores. Every patient gets a telephone follow-up at 8 weeks to evaluate whether pain has decreased, stayed the same or increased and whether patients have reduced their analgesic medications. In addition, we collect data about length of treatment effect so as to plan further treatments.

Our most recent analysis was of 395 patients contacted following initial capsaicin 8% treatment, of which 315 responded (80% response rate). 158 (50%) of respondents were female. The three commonest pain aetiologies were a generalised diagnosis of peripheral neuropathy (34%), scar or post-surgical pain (27%) and post-herpetic neuralgia (15%). 204 (65%) reported pain reduction at 8 weeks, with 101 (32%) reporting no change and 10 (3%) reporting an increase in pain. Over 60% of patients in the three commonest pain aetiology groups reported improved pain following capsaicin therapy (64% peripheral neuropathy, 67% scar pain or post-surgical pain and 63% post-herpetic neuralgia patients). Around a quarter of those diagnosed with scar or post-surgical pain and post-herpetic neuralgia reported that they had reduced analgesic medications following 8% capsaicin therapy (24% and 27%, respectively); however, this was only 13% in patients with the aetiology recorded as peripheral neuropathy.³⁰ Currently, our 8% capsaicin service leads to improved pain at 8 weeks in around two-thirds of the patients treated, and this is consistent across aetiologies. This does not, however, translate to a consistent reduction of analgesic medication, which may be aetiology dependent. However, we have identified a more detailed coding of peripheral neuropathy as an aetiology would help our centre explore these findings further.

Conclusion

High dose of 8% capsaicin patches offers potential benefits over first-line systemic anti-neuropathic therapies due to their lack of systemic effects and minimal side-effect profiles once patches are removed and up to 12 weeks reduction in pain intensity and improved quality of life for a range of neuropathic pain conditions. Delivering a topical capsaicin service is achievable with careful patient selection, preprocedural discussions and planning, specific room set-up and attention to aftercare instructions.