Peak Onset of Captopril
Peak blood levels of captopril occur approximately 60-90 minutes after oral administration, with maximal blood pressure reductions typically observed 60 to 90 minutes after an individual dose. 1, 2
Pharmacokinetic Profile
Peak plasma concentrations are reached 45-60 minutes after oral administration in healthy subjects, with rapid absorption occurring after oral dosing 2, 3
The FDA drug label specifies that peak blood levels occur at about one hour after oral administration 1
Maximal blood pressure reductions occur 60 to 90 minutes after oral administration of an individual dose, which represents the peak pharmacodynamic effect 1
Clinical Implications for Timing
For captopril renography (diagnostic testing for renovascular hypertension), the drug should be administered 50 mg orally taken 60 minutes before performance of renal scintigraphic imaging 4, 5
The relatively short time to peak effect makes captopril suitable for situations requiring relatively prompt blood pressure reduction, though it should not be used for hypertensive emergencies requiring rapid reduction 5
Duration of Effect Considerations
While peak levels occur at 1 hour, the antihypertensive effects persist for a longer period than demonstrable inhibition of circulating ACE, with duration of effect being dose-related 1
The elimination half-life of unchanged captopril is approximately 2 hours, though the clinical effect extends beyond this due to tissue ACE inhibition and formation of reversible disulfide metabolites that serve as a drug reservoir 2, 3
Food reduces absorption by 30-40%, so captopril should be given one hour before meals to ensure optimal and consistent peak levels 1, 2
Comparison with Other ACE Inhibitors
Lisinopril, in contrast, has a much later peak with serum concentrations occurring 6-8 hours after oral dosing, making it unsuitable for situations requiring earlier onset 6
The faster onset of captopril compared to longer-acting ACE inhibitors relates to its more rapid absorption and shorter half-life 2, 3