Antidepressant Drugs

Key points

• • Most antidepressants increase serotonin and/or noradrenaline in the synaptic cleft, though this monoamine model does not fully explain their action, and the mood benefit takes a couple of weeks to appear.
• • Selective serotonin reuptake inhibitors block the serotonin transporter and are widely used because they are safer than older agents in overdose, though an overdose can still be harmful.
• • Tricyclic antidepressants block reuptake of both serotonin and noradrenaline but also block muscarinic, histamine and alpha receptors, causing anticholinergic effects and danger in overdose.
• • Monoamine oxidase inhibitors stop the breakdown of monoamines and can cause a hypertensive crisis with tyramine-rich foods, the so-called cheese reaction.
• • Combining serotonergic drugs can cause serotonin syndrome, with agitation, fever, tremor and overactive reflexes.