ATCvet code: QN06AA04.

Clomipramine has a broad-spectrum of action in blocking the neuronal reuptake of both serotonin (5-HT) and noradrenaline. It therefore possesses the properties of a serotonin re-uptake inhibitor and a tricyclic antidepressant.

The active components in vivo are clomipramine and its major metabolite, desmethylclomipramine. Both clomipramine and desmethylclomipramine contribute to the effects of Clomicalm: clomipramine is a potent and selective 5-HT reuptake inhibitor while desmethylclomipramine is a potent and selective noradrenaline reuptake inhibitor. The principle mechanism of action of clomipramine is potentiation of the effects of 5-HT and noradrenaline in the brain by inhibiting their neuronal reuptake. In addition, clomipramine has anticholinergic effects by antagonism of cholinergic muscarinic receptors.

Clomipramine is well absorbed (>80%) from the gastrointestinal tract in dogs when administered orally but the systemic bioavailability for clomipramine and desmethylclomipramine is 22-26% due to extensive first pass metabolism by the liver. Peak plasma levels of clomipramine and desmethylclomipramine are rapidly reached (approx. 1.5-2.5 hours). The maximal plasma concentrations (Cmax) after oral administration of single doses of 2 mg/kg clomipramine hydrochloride were: 240 nmol/l for clomipramine and 48 nmol/l for desmethylclomipramine. Repeated administration of Clomicalm causes moderate increases in plasma concentrations, accumulation ratios after oral administration twice daily were 1.2 for clomipramine and 1.6 for desmethylclomipramine, with steady state being reached within 3 days. At steady state, the ratio of plasma clomipramine to desmethylclomipramine concentrations is approximately 3:1. Administration of Clomicalm with food causes moderately higher plasma AUC values for clomipramine (25%) and desmethylclomipramine (8%) as compared with administration to fasted dogs. Clomipramine is extensively bound to plasma proteins (>97 %) in dogs. Clomipramine and its metabolites are rapidly distributed in the body in mice, rabbits, and rats with high concentrations being achieved in organs and tissues (including the lungs, heart and brain) and low concentrations remaining in the blood. In dogs, the volume of distribution (VDss) is 3.8 l/kg. The major route of biotransformation of clomipramine is demethylation to desmethylclomipramine. Additional polar metabolites also exist. The elimination t1/2 after intravenous administration of clomipramine hydrochloride in dogs was 6.4 hours for clomipramine and 3.6 hours for desmethylclomipramine. The principle route of excretion in dogs is via the bile (>80%) with the remainder via the urine.