Lacidipine: a calcium antagonist with potent and long-lasting antihypertensive effects in animal studies.

Lacidipine, currently being evaluated as a once-daily antihypertensive agent, acted as a calcium entry blocker on rabbit ear artery (pA2 = 9.4) with a markedly slower onset of action than that of nitrendipine; this effect was not reversed after 9 h of drug washout. Calcium entry blocker activity was also evaluated on nonvascular smooth muscles: Lacidipine showed a more pronounced vascular selectivity than nitrendipine; for both drugs, concentrations required to induce negative inotropic effects in guinea pig ventricular strip were approximately 100 times higher than concentrations needed to antagonize calcium contraction in vascular smooth muscle. In spontaneously hypertensive rats (SHR), by the tail-cuff method, lacidipine (ED25 = 0.35 mg/kg orally, p.o.) proved approximately 30 times more potent, slower in onset, and longer-acting than nitrendipine in reducing blood pressure. These features were confirmed in chronically implanted SHR after oral and intravenous (i.v.) administration (ED25 = 0.19 mg/kg p.o. and 0.006 mg/kg i.v.). A short-lasting tachycardia was detected with both drugs. No evidence of acquired tolerance emerged after repeated oral administrations over a 3-week period. Lacidipine induced a natriuretic effect in saline-loaded SHR at antihypertensive doses. In renal hypertensive dogs, lacidipine proved more potent (three to seven times), slower in onset, and longer-lasting than nitrendipine after p.o. (ED25 = 0.22 mg/kg) and i.v. (ED25 = 0.004 mg/kg) administrations.