Absence of interaction between ramipril, a new ACE-inhibitor, and phenprocoumon, an anticoagulant agent

In a double-blind, placebo-controlled crossover trial, the effects of ramipril, a long-acting non-sulphydryl angiotensin I converting enzyme inhibitor, on phenprocoumon steady-state pharmacodynamics were investigated in 8 healthy male volunteers taking individually fixed doses of phenprocoumon. The results showed that 5 mg ramipril or placebo once daily for 7 days did not alter the anticoagulant response (Quick values) to phenprocoumon after a stabilization phase of 2 weeks. Mean Quick values during the steady-state phase with ramipril and placebo were 67.5% and 69.3%, respectively. The clotting factors II, VII, IX and X as well as protein C decreased in the run-in phase and remained stable both during ramipril and placebo treatment. There were no differences between ramipril or placebo treatments. As the phenprocoumon dosage was kept unchanged during the double-blind phase, the results indicate that ramipril does not interfere with the vitamin K-dependent cascade.