Serotonin syndrome

What is serotonin syndrome?

Serotonin syndrome is a drug induced syndrome characterised by a cluster of dose related adverse effects that are due to increased serotonin concentrations in the central nervous system. It is also known as serotonin toxicity as it covers a spectrum from mild through to severe adverse effects depending, presumably, on the extent of increased serotonin.1 2 Severe toxicity usually occurs only with a combination of two or more serotonergic drugs (even when each is at a therapeutic dose), one of which is generally a monoamine oxidase inhibitor.1 3 Moderate toxicity has been reported with an overdose of a single drug and occasionally from increasing therapeutic doses.1 3 4 Its incidence is difficult to assess, but in large case series of overdoses, moderate serotonin toxicity occurred in 15% of poisonings with selective serotonin reuptake inhibitors (SSRIs).5

In the central nervous system, serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter with many effects, including modification of mood, sleep, vomiting, and pain. Many drugs influence serotonergic neurotransmission, including some antidepressants, appetite suppressants, analgesics, sedatives, antipsychotics, anxiolytics, antimigraine drugs, and antiemetics.1 2

Severe or life threatening effects (rigidity and hyperthermia) seem to result only from stimulation of 5-HT₂ receptors, and only drugs that generally increase serotonergic effects are expected to cause serotonin toxicity. Thus antipsychotics, anxiolytics, antimigraine drugs, and antiemetics, which are serotonin antagonists or have effects on other specific receptors (5-HT_1A, 5-HT_1D, 5-HT₃), do not carry a significant risk of serotonin toxicity.1 …