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  • Most guidelines now recommend an SSRI as the first choice antidepressant if a patient does not respond to non-pharmacological interventions or has a history of moderate or severe depression.
  • SSRIs are usually the first choice antidepressant in older people but specific adverse effects and drug interactions require monitoring.
  • The clinical effects of antidepressants may start after 2-3 weeks treatment but the response should be assessed by an adequate trial, i.e appropriate dose for at least 4-6 weeks. At this stage if there is a partial response a dose increase may be appropriate. If there is no response an alternative may be considered.
  • Citalopram is a good first choice SSRI as it has a lower potential for drug interactions than fluoxetine or paroxetine.
  • Paroxetine requires a shorter washout period when switching SSRIs. However, discontinuation syndrome is common. For information on washout periods and switching see BPJ Issue 1, our 2004 Depression POEM or
  • It is often possible to manage adverse effects before switching treatment, e.g dose reduction in anxiety.
  • Fluoxetine has a longer half life so there are fewer concerns when doses are missed, and discontinuation syndrome is not usually a problem. However, longer washout periods may be required.
  • All SSRIs are likely to be beneficial in treatment of anxiety disorders, despite some having more indications listed on their data sheet than others.
  • SSRIs may be associated with an initial increase in anxiety that peaks over the first week of treatment and then subsides as the treatment effect emerges. Counselling patients about this possibility is important to prevent withdrawal from treatment.
  • SSRIs have a number of significant drug interactions and adverse effects. Some of current interest include; increased risk of bleeding - the risk is higher when SSRIs are used concomitantly with NSAIDs, aspirin, warfarin or low molecular weight heparins; serotonin syndrome especially if taken with other serotonergic agents and hyponatraemia especially in the elderly also taking diuretics.

SSRIs have other indications

All SSRIs are licensed to treat depression. Some have additional indications, reflecting manufacturer's additional applications based on demonstrated efficacy. Fluoxetine is also licensed for bulimia nervosa, obsessive-compulsive disorder (OCD) and premenstrual dysphoric disorder (severe pre-menstrual syndrome); and sertraline for OCD, panic, post-traumatic stress disorder (PTSD) and social phobia. Paroxetine has the broadest range of additional licensed indications: OCD, panic, Social Phobia, Generalised Anxiety Disorder and PTSD. The necessary period of treatment, and dose, may differ between indications. For example, OCD generally responds only to higher doses of SSRI maintained over at least 12 weeks.