Is Phenytoin A Safe Option For Neuropathic Pain?

Today's post from onlinelibrary.wiley.com (see link below)  follows up yesterday's post, in that it comes from the Wiley online library and looks at another anti-epilepsy drug that is being prescribed for neuropathic pain. Yesterday's post concerned Carbamazepine; today's concerns Phenytoin. It has to be said that the assessment stems from 2012 and doctors' opinions about Phenytoin may have changed since then. However, this blog has heard of patients being currently prescribed Phenytoin, possibly because their doctors are trying out alternatives within the same family as carbamazepine, or Lyrica (pregabalin). However, is this safe? This article found no studies to back up opinions one way or the other (in itself a bad sign) but does note that the side effects of Phenytoin shouldn't be underestimated. If you have been prescribed Phenytoin, it may be worth having another discussion with your doctor or specialist to discover whether it really is the best option for you.
 

Phenytoin for neuropathic pain and fibromyalgia in adults
Fraser Birse, Sheena Derry*, R Andrew Moore
Editorial Group: Cochrane Pain, Palliative and Supportive Care Group
Published Online: 16 MAY 2012
Assessed as up-to-date: 4 APR 2012
DOI: 10.1002/14651858.CD009485.pub2

Copyright © 2014 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

Abstract

Background

Antiepileptic drugs have been used in pain management since the 1960s; some have shown efficacy in treating different neuropathic pain conditions. Phenytoin is an established antiepileptic drug that has been used occasionally to treat intractable trigeminal neuralgia.

Objectives

To assess the analgesic efficacy and adverse effects of the antiepileptic drug phenytoin in neuropathic pain and fibromyalgia.

Search methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 2), MEDLINE, and EMBASE to 28 February 2012, together with reference lists of retrieved papers and reviews, and ClinicalTrials.gov.

Selection criteria

We planned to include randomised, double-blind studies of eight weeks duration or longer, comparing phenytoin with placebo or another active treatment in chronic neuropathic pain or fibromyalgia.

Data collection and analysis

Two review authors would independently extract data for efficacy and adverse events, and examine issues of study quality.

Main results

We did not identify any studies that satisfied the inclusion criteria.

Authors' conclusions

This review uncovered no evidence of sufficient quality to support the use of phenytoin in chronic neuropathic pain or fibromyalgia.

Plain language summary

Phenytoin for neuropathic pain and fibromyalgia in adults

Nerves which have been damaged by injury or disease can continue to produce pain. This type of pain is called neuropathic pain. Some antiepileptic medications can help neuropathic pain. Phenytoin is an antiepileptic medication, and the aim of this review was to assess how effective phenytoin is for neuropathic pain and fibromyalgia. We identified no good quality studies of phenytoin used in this situation. When used to treat epilepsy, phenytoin can cause potentially troublesome adverse events, affecting nervous tissue, the blood, and unborn children. Based on current evidence, phenytoin cannot be recommended for treating neuropathic pain. Other antiepileptic drugs such as pregabalin, gabapentin, and carbamazepine have been shown to be of value in neuropathic pain.

http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD009485.pub2/abstract;jsessionid=4448E010B2DE6127557095C833E897CC.f01t04