Pregabalin: its efficacy, safety and tolerability profile in generalized anxiety

Pregabalin is a structural analogue of gamma-aminobutyric acid (GABA), one of the key inhibitory neurotransmitters in the brain. Its mode of action is believed to be mediated by the alpha-2-delta-1 subunit protein of voltage-gated calcium channels to bring about its anxiolytic, anticonvulsant and antinociceptive effects. Pregabalin has linear pharmacokinetics, undergoes minimal metabolism and is excreted largely unchanged. It has a mean elimination half-life of 6.3 hours. Pregabalin's anxiolytic activity in generalized anxiety disorder has been demonstrated in seven acute randomized, double-blind, placebo-controlled trials of four to eight weeks duration, and in one six-month relapse-prevention study at doses of 150-600 mg/day using twice-daily or three-times-daily regimes. The magnitude of pregabalin's anxiolytic effects was similar to that of alprazolam, lorazepam or venlafaxine. However, pregabalin had a more consistent effect on psychic and somatic anxiety factors than the active comparators. Its speed of onset was apparent within one week - similar to the benzodiazepines, but faster than that of venlafaxine. Moreover, pregabalin's anxiolytic effect was apparent in patients with moderate or severe baseline anxiety and high or low baseline severity of sub-syndromic depression. A long-term, 26-week, open-label study showed that pregabalin's anxiolytic effects were maintained, although the fixed-dose design may have contributed to a high attrition rate. Pregabalin showed less cognitive and psychomotor impairment than alprazolam, and it showed different effects on sleep architecture to the latter in terms of REM sleep latency and slow wave stage 3/4 sleep. The most frequently reported adverse events were dizziness and somnolence, although tolerance to these developed within a few weeks. Withdrawal symptoms during a one-week taper phase were mild and were similar after both acute and chronic administration.