Tetrandrine

Tetrandrine is the most well-characterized Ca2+ channel blocker of plant origin. It is an L-type Ca2+ channel blocker with a binding site at the benzothiazepine receptor of the channel. Tetrandrine also blocks T-type Ca2+ channels. Tetrandrine exerts negative inotropic and chronotropic as well as antiarrhythmic effects, without altering cardiac excitability. It also reduces myocardial oxygen consumption and increases coronary blood flow and myocardial perfusion. Tetrandrine relaxes both KCl- and norepinephrine-contracted vessels. It also inhibits platelet activation by various stimuli. Tetrandrine exerts systemic hypotensive and vasodilatory effects. Beneficial effects of tetrandrine have been reported in disease states such as hypertension, arrhythmias, angina, pulmonary and portal hypertension. Experimental studies also showed that tetrandrine can protect animals from ischemia-reperfusion injury; this effect is possibly related to inhibition of lipid peroxidation and/or scavenging of free radicals. Tetrandrine is not in clinical use in countries other than China, and its published clinical pharmacological and pharmacokinetic data are inadequate in terms of quantity and quality.