Liposomal topical capsaicin in post-herpetic neuralgia: a safety pilot study

Abstract

Topical treatments have gained popularity for general use as an adjunct to systemic drugs in neuropathic pain, but their use produces variable clinical results and local adverse events. Objective: To evaluate the safety and analgesic effect of a formulation of liposomal capsaicin (LC) (0.025%) in patients with post herpetic neuralgia (PHN). Method: Patients who remained symptomatic after first-and second-line treatment were randomized to receive LC for six weeks in a placebo-controlled, crossover design study. Clinical assessment was performed at baseline, in the second, fourth and sixth week of treatment. Results: Thirteen patients completed both treatment periods. Visual Analog Scale (VAS) was significantly decreased after the end of the study (p = 0.008), however the effect of treatment was not significant (p = 0.076). There was no difference on global impression of change and other pain characteristics. LC was safe and well tolerated. However, at the concentration used, its analgesic effects were marginal and not significant.Keywords: capsaicin, pain, neuralgia, analgesia, rash, adverse events. RESUMOOs tratamentos tópicos ganharam popularidade para uso geral como um adjuvante de medicamentos sistêmicos na dor neuropática, mas seu uso produz resultados clínicos variáveis e eventos adversos locais. Objetivo: Avaliar o efeito de segurança e analgesia de uma formulação de capsaicina lipossomal (LC) (0,025%) em pacientes com neuralgia pós-herpética. Método: Os pacientes que permaneceram sintomáticos após tratamento de primeira e de segunda linha foram randomizados para receber LC durante seis semanas em um estudo cruzado controlado por placebo. A avaliação clínica foi realizada no início do estudo, na segunda, quarta e sexta semana de tratamento. Resultados: Treze pacientes completaram dois períodos de tratamento. Escala Visual Analógica diminuiu significativamente após o final do estudo (p = 0,008), no entanto, o efeito do tratamento não era significativo (p = 0,076). Não houve diferença na impressão global de mudança e de outras características da dor. LC foi segura e bem tolerada. No entanto, para a concentração utilizada, os seus efeitos analgésicos foram marginais e não significativos.Palavras-chave: capsaicina, dor, neuralgia, analgesia, efeitos adversos.Neuropathic pain is present in 7% of the general population 1,2 , and despite the multiple treatment approaches, its current management only provides modest pain relief 3,4 . There has been renewed interest in the development of topical treatments that can decrease pain with lower side effects 4 . However, the use of topical treatments has provided variable analgesic results 5,6 and is associated with side effects mainly related to skin reactions and pain in the application site 7,8 . One approach to increase the therapeutic index (i.e., the measurement of efficacy over toxicity) is to employ delivery systems that can release the medication to its target with fewer side effects related to local inflammation 9 . Topical capsaicin has been used in th...

Capsaicin, Nociception and Pain

“…These patches contain 640 mcg/cm 2 synthetic capsaicin with a total dose of 179 mg in one patch [228]. Lower doses showed no clinical benefits [229,230,231] or only short-term efficacy [232,233]. In general, it seems that the vanilloid is effective in the treatment of neuropathic but not inflammatory pain.…”

The Safety of Medications used to Treat Peripheral Neuropathic Pain, Part 2 (Opioids, Cannabinoids and Other Drugs): review of Double-Blind, Placebo-Controlled, Randomized Clinical Trials

“…Another trial assessed a 0.025 liposomal capsaicin lotion in 14 post herpetic neuropathic patients for 6 weeks [60]. Yet another trial assessed a 0.1 mg dose capsaicin injection in 30 Morton's neuroma patients versus placebo (28 patients) [61].…”

“…Hence, local skin irritation, often mild and transient but possibly leading to withdrawal, was common, while systemic adverse effects were rare when low concentration capsaicin lotions were tested. Interestingly, liposomal topical capsaicin was tested in a small number of postherpetic patients [60] to increase the therapeutic index. This delivery system was designed to deliver the medication to its target with fewer adverse effects.…”

Harnessing the Therapeutic Potential of Capsaicin and Its Analogues in Pain and Other Diseases

“…Moreover, several capsaicin analogues obtained naturally or synthetically guided in the identification of novel drugs with less or no lethal effects. In an attempt to minimize local side effects and increase the drug tolerability, several novel technologies have been introduced to improve capsaicin delivery [222,223,224,225]. The future challenges that remain to be addressed include determining the effective dose levels of capsaicin, and efficient mode of administration.…”