Pregabalin, the pharmacologically active S-enantiomer of 3-aminomethyl-5-methyl-hexanoic acid, has a similar pharmacological profile to that of its developmental predecessor gabapentin, but showed greater analgesic activity in rodent models of neuropathic pain. The exact mechanism of action of pregabalin is unclear, although it may reduce excitatory neurotransmitter release by binding to the alpha2-delta protein subunit of voltage-gated calcium channels. Oral pregabalin at fixed dosages of 300 and 600 mg/day, administered three times daily, was superior to placebo in relieving pain and improving pain-related sleep interference in three randomised, double-blind, multicentre studies of 5-8 weeks' duration in a total of 724 evaluable patients with painful diabetic peripheral neuropathy (DPN). Significant reductions in weekly mean pain scores (primary endpoint) and sleep interference scores were observed at 1 week and sustained thereafter. A significant reduction in pain was apparent on the first day of treatment with pregabalin 300 mg/day. Twice daily fixed (600 mg/day) or flexible (150-600 mg/day) pregabalin was also effective in reducing pain and sleep interference in two 12-week placebo-controlled trials in a total of 733 randomised DPN patients. Pregabalin was well tolerated in DPN patients; mild-to-moderate dizziness, somnolence and peripheral oedema were the most common adverse events.