Do Captopril Renogram and Losartan Renogram Influence the Choice of Drug (Angiotensin Converting Enzyme Inhibitor/Angiotensin II Receptor Blocker) to be Initiated in Renal Patients?

Abstract

The objectives of this study were to investigate the effects of angiotensin converting enzyme (ACE) inhibitors and angiotensin (AT) II receptor blockers on glomerular filtration rate (GFR) as measured by radionuclide renogram study, and to assess the value of changes in GFR modification with AT-II receptor blocker/ACE inhibitor in determining the drug choice between ACE inhibitors and AT-II receptor blockers. Methods: A total of 14 patients with type 2 diabetes or hypertension were subjected to baseline diethylene triamine pentaacetic acid (DTPA) renogram followed by captopril and losartan renograms. The patients were followed in a prospective randomized controlled crossover trial. Patients were treated with either enalapril or losartan initially for 6 months, followed by the other drug in the later 6 months of the study period. Patients with renal arterial disease, obstructive uropathy, urinary tract infection, acute renal failure or serum creatinine more than 3 mg/dL were excluded from the study. Our data showed that irrespective of the initial choice of drug, either ACE inhibitor or AT-II receptor blocker, there was an initial fall in GFR (noticed at 3 and 6 months) followed by an increase in GFR at the end of 1 year. But neither the initial fall in GFR nor serum creatinine at the end of 6 months were different. This shows that initial fall in GFR might not be associated with a rise in serum creatinine. Patients may respond differently after intervention with captopril or losartan as evidenced by radionuclide renogram study. The acute decline in GFR after captopril and losartan may be a pointer to the utility of radionuclide DTPA renogram study in choosing which drug - ACE inhibitor or AT-II receptor blocker - to use in patients requiring them. An acute increase in GFR may not always suggest lack of benefit with that particular drug. This is especially true with AT-II receptor blockers, where the effects of AT2 receptors appear to have an influential role.