Combined inhibition of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) produces cardiovascular effects greater than those elicited by selective inhibition of either enzyme alone. Dual metalloprotease inhibitors are single molecules that inhibit both NEP and ACE and produce cardiovascular effects in animal models similar to those elicited by the combination of NEP and ACE inhibitors. The purpose of this study was to determined the duration of antihypertensive activity of the dual metalloprotease inhibitor omapatrilat in rodent models of hypertension. Omapatrilat inhibited NEP (Ki = 9 nmol/L) and ACE (Ki = 6 nmol/L) activities in vitro and inhibited the pressor response to angiotensin I in rats after intravenous administration with a potency and duration of action similar to those of the long acting ACE inhibitor fosinoprilat. After single dose administration, omapatrilat lowered mean arterial blood pressure (aortic catheter) in sodium depleted spontaneously hypertensive rats (high renin model) from 148+/-5 to 106+/-3 mm Hg (baseline to 24 h), in deoxycorticosterone acetate-salt hypertensive rats (low renin) from 167+/-4 to 141+/-5 mm Hg and in spontaneously hypertensive rats (normal renin) from 162+/-4 to 138+/-3 mm Hg (P < .05 at 24 h v vehicle in all models). After oral administration, omapatrilat (100 micromol/kg/day) persistently lowered systolic blood pressure (tail cuff) in spontaneously hypertensive rats during 11 days of treatment; at 24 h after dosing on day 12, mean arterial pressure (aortic catheter) was lower (P < .05) in the group receiving omapatrilat (133+/-5 mm Hg) than in the group receiving vehicle (149+/-2 mm Hg). The results indicate that omapatrilat is a potent dual metalloprotease inhibitor of NEP and ACE with long lasting, oral antihypertensive effects in low, normal, and high renin models of hypertension. Omapatrilat has the potential to be an effective, broad spectrum antihypertensive agent.