The following study found topical lidocaine to provide sustained relief in patients suffering from neuropathic pain -“Long-term treatment of neuropathic pain with a 5% lidocaine medicated plaster” (Eur J Anaesthesiol. 2010 Feb;27(2):169-73).

BACKGROUND AND OBJECTIVE: The 5% lidocaine medicated plaster is a topical treatment for peripheral neuropathic pain symptoms (e.g. burning, shooting and stabbing pain) and is registered for the treatment of postherpetic neuralgia. This study examined the efficacy and tolerability of long-term treatment with the 5% lidocaine medicated plaster in patients with localized neuropathic pain conditions.

METHODS: Twenty patients with localized neuropathic pain [postoperative neuropathic pain (n = 14); complex regional pain syndrome (n = 2); and postherpetic neuralgia (n = 4)], who had been successfully treated with 5% lidocaine medicated plaster, were followed up by telephone interview after 3 and 5 years. Questions were related to the efficacy, development of tolerance, tolerability, wear time and comfort of the plaster.

RESULTS: At 3 years, 10 out of 20 (50%) initial responders were still using the plasters with no decline in analgesic efficacy. After 5 years, eight of the original 20 responders (40%) maintained treatment and continued to experience effective pain relief. The 12 responders who discontinued treatment did so because they no longer required analgesic therapy (n = 4); their health insurer refused to fund treatment (n = 2); they were lost to follow-up (n = 1); or had died from an illness unrelated to plaster treatment (n = 5). No patient discontinued because of inadequate analgesia or intolerable side effects. Reversible erythema occurred in two patients wearing the plaster for more than 16 h. There were no systemic side effects.

CONCLUSION: The 5% lidocaine medicated plaster provides sustained pain relief over long-term treatment in patients with neuropathic pain of various causes and is well tolerated. PMID: 20010108

The following case report suggests an analgesic dose-response effect for topical amitriptyline in painful neuropathy – “High Doses of Topical Amitriptyline in Neuropathic Pain: Two Cases and Literature Review” (Pain Pract. 2011 Jun 16).

“Severe chronic neuropathic pain is a challenge to treat, and due to adverse effects of classical oral medication, optimal and effective dose levels are difficult to reach. Therefore, administration of topical analgesics might be an option, due to reduced adverse effects, and increased patient compliance.

The aim of this article is to describe two cases treated effectively with topical amitriptyline 5% and 10%, the highest dosage described to date. The first patient was a 39-year-old man, suffering from severe intractable neuropathic pain in feet and hands, due to diabetes mellitus type II (DM-II). After application of amitriptyline 5% the patient experienced a complete relieve only in the hands, whereas after application of amitriptyline 10%, a total reduction of pain occurred within 20 minutes, lasting the whole day. The second patient was a 57-year-old man, suffering for 10 years from progressive sensory disturbances in both feet and increasing pain due to chronic idiopathic axonal polyneuropathy (CIAP). Amitriptyline 5% cream reduced pain in the toes nearly completely, but this was not the case in the heels. Amitriptyline 10% reduced pain in the feet, however, systemic adverse effects occurred, mainly drowsiness. The patient decided to stop topical treatment because of these adverse effects.

These two cases suggest an analgesic dose-response effect of topical amitriptyline in painful neuropathy. Systemic adverse effects should be taken into account.” PMID: 21676162

We can compound lidocaine and amitriptyline together into one transdermal cream.