Gabapentin for the Treatment of PHN
Among pain syndromes, postherpetic neuralgia (PHN) and diabetic neuropathy (DMN) are often among the most challenging for clinicians and patients alike. Two recent reports evaluate the role of gabapentin in these clinical circumstances. In the trial of gabapentin for painful DMN (n = 165), subjects underwent four weeks titration of active drug from 900 mg to 3600 mg/d, administered tid in 300 mg capsules, followed by four weeks of full-dose treatment. Study subjects, 75% of whom had Type II Diabetes, had been symptomatic for a minimum of one year. Lower extremity pain was the most common DMN manifestation.
In the PHN trial, zoster patients (n = 229) suffering at least three months pain received a similar titration phase followed by four weeks active treatment at 3600 mg/d. Both trials were randomized, double-blind, and placebo controlled.
Gabapentin treatment was found to be effective in both studies, with modest incidence of side effects, primarily dizziness and somnolence, though rarely did an adverse side effect lead to withdrawal from the study. In addition to pain alleviation, sleep interference was substantially improved. The efficacy of pain relief was of equal magnitude to that demonstrated for tricyclic therapy, with more rapid onset.
The authors suggest that gabapentin may be considered both as a first-line single entity for management of PHN or DMN, and as additive therapy with other traditional modalities such as tricyclics, since the pharmacodynamic profile of gabapentin is free of drug interactions.
Rowbotham M, et al. JAMA 1998;280: 1827-1842; Backonja M, et al. JAMA 1998;280:1831-1836.