What is the recommended amount of captopril to be given orally an hour before renal imaging in a hypertension study?

In renal imaging, particularly for studies assessing renal blood flow or evaluating renovascular hypertension, captopril is used as an angiotensin-converting enzyme (ACE) inhibitor to provoke changes in renal function that can be detected on imaging. The purpose of administering captopril is to induce preferential dilation of the renal artery in patients with renal artery stenosis, revealing differences in kidney function through imaging.

The recommended dosage of captopril for this purpose is typically in the range of 25-50 mg, ideally taken one hour before the imaging procedure. This dosage is sufficient to achieve significant pharmacological effects, leading to changes in renal hemodynamics that can be effectively assessed during imaging.

The other dosages listed may either fall short of the effective threshold or exceed typical clinical use, which is why they are less appropriate for this context. The specific range provided ensures that the patient receives an effective dose while minimizing the risk of side effects or complications related to over-medication.