Elias: With captopril, you can have a reduction in BP as early as 60-90 minutes after one dose. But the duration of the effect is dose related and the reduction in your blood pressure is usually progressive.
SO, to achieve the maximum and best theraputic results, sometimes your doctor will want to monitor you one week later up to 4 weeks. (Usually though, within two weeks you know if it's doing the job)
Hope this helps.
zuzu xx