Panic disorder is a
chronic condition for many patients and can be socially, emotionally and occupationally disabling. Until recently,
clomipramine and
alprazolam were the only drugs approved for its treatment. While widely used in the US and Europe, both belong to
drug classes (tricyclics and
benzodiazepines) with well-recognised side effects that can be problematic and thus limit their use. Recently,
paroxetine became the first
selective serotonin reuptake inhibitor to receive approval and licensing for
panic disorder. The short- and long-term efficacy and tolerability of
paroxetine in
panic disorder has been established in clinical trials of almost 1,000 patients meeting Diagnostic and Statistical Manual (DSM)-IIIR criteria for
panic disorder, with or without
agoraphobia. In a 12-week double-blind study of 120 panic patients receiving standardised cognitive therapy,
paroxetine was significantly more effective than placebo in reducing
panic attack frequency. In a 12-week placebo-controlled comparison in 367 panic patients,
paroxetine was at least as effective as
clomipramine and better tolerated. There was also some evidence that
paroxetine had an earlier onset of action than
clomipramine. A 9-month extension of the placebo-controlled comparison with
clomipramine showed that the efficacy of
paroxetine and
clomipramine is maintained when treatment is continued into the longer term. In a
relapse prevention study, 105 responders to 3 months' treatment with
paroxetine or placebo were re-randomised, either to continue existing treatment or to receive placebo for 3 months. Only 5% of patients who continued to take
paroxetine experienced a relapse compared with 30% of those who switched to placebo (P = 0.002).
Paroxetine was generally well tolerated. In the short-term trials, the frequency of withdrawals due to adverse events (7.3%) was lower than that for placebo (11.4%) or
clomipramine (14.9%). In the longer term, the dropout rate due to adverse events increased in the
clomipramine group (19.0%) but was unchanged in the
paroxetine group (7.4%). Since most patients with
panic disorder will require prolonged treatment, the long-term tolerability of
paroxetine and its lack of potential for dependence are important advantages that will encourage good compliance with treatment and improve the quality of life of patients.