Selective serotonin reuptake inhibitors (SSRIs) are a major class of antidepressant medication. In 2009 over 21 million prescriptions for SSRIs were dispensed in England in the primary-care setting; SSRIs accounted for about 55% of antidepressant prescriptions.
SSRIs inhibit presynaptic reuptake of the neurotransmitter serotonin (5-hydroxytryptamine, 5HT), increasing the availability of serotonin at synapses and enhancing stimulation of postsynaptic neurones. Changes in receptor sensitivity (eg downregulation) arising from increased synaptic serotonin are thought to contribute to the antidepressant activity of SSRIs.
The adverse effects of SSRIs are distinct from those of tricyclic antidepressants; SSRIs have less marked antimuscarinic (anticholinergic) activity and, in overdosage, the characteristic features of tricyclic antidepressant poisoning—respiratory failure, defective cardiac conduction and coma—are largely absent in overdose with SSRIs. Characteristic adverse effects—such as those affecting the gastrointestinal tract and sexual function—can be attributed to the stimulation of 5HT receptors.
This learning module is derived largely from summaries of product characteristics (which, in turn, are based on rigorous evaluation of submitted evidence). Supplementary sources such as guidelines from NICE are used to expand on advice on managing specific risks of SSRIs; however, general advice on the management of depression and other disorders is not covered.
You should consult other resources (including evidence-based national guidelines) for advice on selecting an intervention from the range of treatment options available, taking into account the severity of illness and other clinical circumstances.
This learning module will be updated from time to time. Do please contact webusability@mhra.gsi.gov.uk with feedback on any aspect of the module.
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