Captopril: Pharmacology, Metabolism, and Disposition

Abstract

By inhibiting ACE, captopril blocks the conversion of AI or AII and augments the effects of bradykinin both in vitro and in vivo. In rats, dogs, and monkeys with 2-kidney renal hypertension, orally administered captopril rapidly and markedly reduces blood pressure; this antihypertensive effect apparently occurs via a renin-dependent mechanism; that is, the inhibition of ACE. In 1-kidney renal hypertension studies in rats and dogs, it was determined that oral doses of captopril markedly lowered blood pressure, but only after several days of dosing; the mechanism is thought to be non-renin dependent. In SHR, daily oral doses of captopril progressively lowered blood pressure; normal levels were attained by the sixth month. In all species studied, the reduction in blood pressure resulted from a reduction in total peripheral resistance; cardiac output remained unchanged or increased. In humans, captopril reduces blood pressure in patients with essential hypertension with low, normal, and high renin levels, and in patients with renovascular hypertension and hypertension associated with chronic renal failure. In hypertensive patients with high plasma renin activity, captopril apparently exerts most of its pharmacologic effects through inhibition of ACE. The means by which captopril reduces high blood pressure associated with low or normal PRA is not known, but it is clear that captopril does not act on an overactive plasma renin-angiotensin system in these cases. The antihypertensive effect of captopril is enhanced when it is given in combination with a diuretic or after salt depletion. Captopril was rapidly and well absorbed in all species tested, including man. Studies in rodents indicated that ingestion of food caused a reduction in the extent of absorption and bioavailability of captopril. Captopril and/or its metabolites were distributed extensively and rapidly throughout most tissues of normal rats; no radioactivity was detected in the brain. In vitro and in vivo, captopril formed disulfide bonds with albumin and other proteins. This binding was reversible in nature. In vitro studies in blood indicates that the disulfide dimer of captopril and mixed disulfides of captopril with L-cysteine and glutathione were formed. In intact blood cells, captopril remained in the reduced form (sulfhydryl), whereas in whole blood or plasma, captopril was converted to its disulfide dimer and other oxidative products. Biotransformation of captopril may involve both enzymatic and nonenzymatic processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Captopril Prevents Experimental Autoimmune Myocarditis

“…These complications are typically treated with diuretics, digitalis, ␤ blockers, and vasodilators, such as angiotensin II receptor antagonists and angiotensin-converting enzyme (ACE) 4 inhibitors (9). One commonly prescribed ACE inhibitor is captopril, which binds to ACE via its peptide-binding pocket and inhibits the functions of ACE, particularly the formation of angiotensin II from angiotensin I and the breakdown of bradykinin (10). Among the many ACE inhibitors and angiotensin II receptor antagonists, captopril has been shown to modulate chemotaxis, motility, adhesion, differentiation, activation, and cytokine and chemokine production of immune cells (reviewed in Ref.…”

Comparison of angiotensin converting enzyme inhibition and angiotensin II receptor blockade for the prevention of experimental autoimmune myocarditis

“…*p < 0.05 compared to the group receiving water. (20) 109.7 ± 5.5 Ova/CFA Captopril (9) 272.9 ± 10.2 * Losartan (5) 108.4 ± 5.4 No drug (10) 106.0 ± 5.5 PBS/CFA Captopril (9) 265.3 ± 12.7 * Losartan (5) 141.0 ± 7.1 No drug (9) 133 …”

“…In particular, it inhibits the formation of Ang II from Ang I and prevents the degradation of bradykinin [9,10]. By interfering with the renin-angiotensin system and bradykinin pathways, captopril reduces sytemic arterial pressure, peripheral vascular resistance and cardiac filling pressure, and increases cardiac output.…”

Recent Advances in Pharmaceutical Chemistry—angiotensin-Converting Enzyme Inhibitors

“…3 ) between captopril, captopril disulphide and the mixed disulphides formed with endogenous thiolcontaining molescules have been established in vitro and in vivo in blood. This complex exchange will not only affect the distribution of the free drug in tissue, but, because the disulphides are relatively more stable than the free thiol, they act as a latent depot of drug and thus liberate captopril by either NADH-or NADPH-dependent reductions of the disulphide bond or through disulphide exchange (21).…”

“…As there are various reviews (21,4942) that cover the pharmacological aspects of the ACE-inhibitors, only selected aspects of their pharmacokinetics will be considered. After oral administration, all the ACE-inhibitors are rapidly absorbed, with the exception of lisinopril (Table 3).…”