Mianserin: Pharmacological and clinical correlates

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Abstract
Antidepressants interact with a variety of neurotransmitter receptors to exert both their therapeutic and side effects. However, the problems of anticholinergic and cardiovascular side effects of the older antidepressants, irritating at therapeutic dose but potentially lethal in overdose, have been largely solved by introduction of newer atypical drugs which enhance patient compliance and are safer in overdose. Mianserin is an established atypical antidepressant which exerts its therapeutic action principally via antagonism at presynaptic α2 adrenoceptors controlling noradrenaline release rather than by inhibition of monoamine reuptake or oxidase. Serotonin (5-HT) antagonism may play a contributory role; mianserin is an antagonist at 5-HT1c, 5-HT2 and 5-HT3 receptors and enhances 5-HT neurotransmission upon chronic administration. Mianserin lacks anticholinergic activity and has no effects upon cardiac conduction, but it produces initial sedation via antagonism at histamine H1-receptors. This profile is reflected in its relative safety in overdose where excessive drowsiness is the commonest problem. In contrast cardiac arrhythmias are common in overdosage with tricyclic antidepressants, arising from their quinidine-like proarrhythmogenic effects upon cardiac conduction and aggravated by their anticholinergic-induced sinus tachycardia, and are the principal cause of death. The overall fatality risk of mianserin from overdosage and adverse drug reactions is lower than that of other established antidepressants. The diverse pharmacology of mianserin suggests that it may also have therapeutic utility in other psychiatric illnesses such as anxiety, schizophrenia and opiate withdrawal, as well as in sleep disorders and migraine, and emesis and peptic ulcer.