Topical amitriptyline and ketamine for post-herpetic neuralgia and other forms of neuropathic pain

ABSTRACT

Introduction: Neuropathic pain (NP) has several therapeutic options but efficacy is limited and adverse effects occur, such that additional treatment options are needed. A topical formulation containing amitriptyline 4% and ketamine 2% (AmiKet) may provide such an option.

Areas covered: This report summarizes both published and unpublished results of clinical trials with AmiKet. In post-herpetic neuralgia (PHN), AmiKet produces a significant analgesia which is comparable to that produced by oral gabapentin. In diabetic painful neuropathy, AmiKet showed a strong trend towards pain reduction. In mixed neuropathic pain, case series reports suggest a favourable response rate, but are limited by trial characteristics. AmiKet is absorbed minimally following topical administration. Over 700 patients have now received topical AmiKet in clinical regimens, and it is well-tolerated with the adverse effects mainly being application site reactions. Both agents are polymodal, and several mechanisms may contribute to the peripheral efficacy of AmiKet.

Expert opinion: Topical AmiKet has the potential to be a first-line treatment option for PHN, and to be useful in other NP conditions. Furthermore, AmiKet has the potential to be an adjunct to systemic therapies, with the targeting of a peripheral compartment in addition to central sites of action representing a rational drug combination.

KEYWORDS:

• amitriptyline
• ketamine
• neuropathic pain
• topical analgesics

Acknowledgement

The authors thank Jennifer S. Gewandter for helpful comments on the manuscript.

Declaration of interest

Immune Pharmaceuticals supported the writing of this article. J Sawynok has received licence fees from EpiCept and Immune Pharmaceuticals. C Zinger has been a consultant for Immune Pharmaceuticals. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.