Mianserin

Mianserin is a tetracyclic antidepressant. It does not appear to have significant anti-cholinergic properties, but has a marked sedative action. Unlike amitriptyline, it does not prevent the peripheral re-uptake of noradrenaline; it blocks presynaptic alpha-adrenoceptors and increases the turnover of brain noradrenaline. It has little effect on central serotonin uptake but has been shown to increase peripheral serotonin uptake in depressed subjects. It has antihistamine properties. Although many of the effects of mianserin differ from those of amitriptyline, its activity in depression is similar. Like amitriptyline, its mode of action in depression is not fully understood.

Absorption

Mianserin is readily absorbed from the gastro-intestinal tract, but its bioavailability is reduced to about 70% by extensive first-pass metabolism in the liver.

Distribution

Mianserin is widely distributed throughout the body and is extensively bound to plasma proteins. It has been found to have a biphasic plasma half-life with the duration of the terminal phase ranging from 6 to 39 hours. Although plasma concentrations of mianserin vary widely between individuals there are some indications of a correlation with therapeutic response.

Mianserin crosses the blood-brain barrier. Studies in-vitro and in animals have suggested that only small amounts cross the placenta and are excreted in breast milk.

Biotransformation

Paths of metabolism of mianserin include aromatic hydroxylation, N-oxidation and N-demethylation.

Elimination

Mianserin is excreted in the urine, almost entirely as its metabolites, either free or in conjugated form; some is also found in the faeces.

No further data.