Pharmacological Classification: Antiemetics and antivertigo preparations.
Pharmacology: Cinnarizine: Cinnarizine inhibits contractions of vascular smooth muscle cells by blocking calcium channels. Cinnarizine increases erythrocyte deformability and decreases blood viscosity in vitro. Cinnarizine inhibits stimulation of the vestibular system.
The peak plasma levels of cinnarizine are obtained 1-3 hrs after intake. Cinnarizine disappears from plasma with a t½ of 4 hrs. Cinnarizine is completely metabolised. About 1/3 of these metabolites are eliminated in the urine and 2/3 in the faeces. The plasma protein-binding of cinnarizine is 91%.
Domperidone: Domperidone is a dopamine-receptor blocking agent. Its action on the dopamine receptors in the chemo-emetic trigger zone produces an antiemetic effect.
Domperidone does not cross the blood-brain barrier to any appreciable degree and so exerts relatively little effect on cerebral dopaminergic receptors.
Domperidone has been shown to increase the duration of antral and duodenal contractions to increase gastric emptying.
Domperidone does not alter gastric secretions and has no effect on intracranial pressure or on the cardiovascular system.
Domperidone is rapidly absorbed with peak plasma concentrations approximately 1 hr after oral administration.
The absolute bioavailability of oral domperidone is low (approximately 15%) due to first-pass hepatic and intestinal metabolism.
Domperidone is 91-93% bound to plasma proteins. The plasma t½ after a single oral dose is 7-9 hrs in healthy subjects but is prolonged in patients with severe renal insufficiency.
Urinary and faecal excretion amount to 31% and 66% of the oral dose, respectively. The proportion of drug excreted unchanged is small (approximately 1% of urinary and 10% of faecal excretion).