Pregabalin: in the treatment of postherpetic neuralgia

Pregabalin is the pharmacologically active S-enantiomer of 3-aminomethyl-5-methyl-hexanoic acid. It has a similar pharmacological profile to that of its developmental predecessor gabapentin, but had greater analgesic activity in rodent models of neuropathic pain. Pregabalin is thought to act by reducing the excessive release of several excitatory neurotransmitters by binding to the alpha(2)-delta protein subunit of voltage-gated calcium channels. Oral pregabalin 150-600 mg/day, administered in two or three divided doses, was significantly more effective than placebo in relieving pain and improving pain-related sleep interference in four randomized, double-blind, multicentre studies of 4-13 weeks' duration in patients with postherpetic neuralgia (PHN). Pregabalin achieved a faster onset of pain relief than placebo. The median times to the onset of pain relief with fixed and flexible doses of pregabalin were 1.5 and 3.5 days compared with >4 weeks with placebo. Pregabalin was generally well tolerated when titrated over 1 week to fixed dosages (maximum 600 mg/day) in clinical trials in mostly elderly PHN patients. Adverse events were usually mild to moderate in severity.