Knowing of Drug: Captopril

Captopril

Definition

Captopril is an angiotensin-converting enzyme inhibitor (ACE inhibitor) used for the treatment of hypertension and some types of congestive heart failure. Captopril was the first ACE inhibitor developed and was considered a breakthrough both because of its novel mechanism of action and also because of the revolutionary development process. Captopril is commonly marketed by Bristol-Myers Squibb under the trade name Capoten

Clinical Use

Captopril's main uses are based on its vasodilatation and inhibition of some renal function activities. These benefits are most clearly seen in the following conditions:

1) Hypertension

2) Cardiac conditions such as post myocardial infarction and congestive heart failure

3) Preservation of kidney function in diabetic nephropathy

Additionally, it has shown mood-elevating properties in some patients. This is consistent with the observation that animal screening models indicate putative antidepressant activity for this compound, although there has been one negative study. Formal clinical trials in depressed patients have not been reported.

History

Captopril was developed in 1975 by three researchers at the U.S. drug company Squibb (now Bristol-Myers Squibb): Miguel Ondetti, Bernard Rubin and David Cushman. Squibb filed for U.S. patent protection on the drug in February 1976 and U.S. Patent 4,046,889 was granted in September 1977.

The development of captopril was amongst the earliest successes of the revolutionary concept of structure-based drug design. The renin-angiontensin-aldosterone system had been extensively studied in the mid-20th century and it had been decided that this system presented several opportune targets in the development of novel treatments for hypertension. The first two targets that were attempted were renin and ACE. Captopril was the culmination of efforts by Squibb's laboratories to develop an ACE inhibitor.

Ondetti, Cushman and colleagues built on work that had been done in the 1960s by a team of researchers led by John Vane at the Royal College of Surgeons of England. The first breakthrough was made by Kevin K.F.Ng in 1967 when he found that the conversion of angiotensin I to angiotensin II took place in the pulmonary circulation instead of in the plasma. In contrast, Sergio Ferreira found that bradykinin disappeared in its passage through the pulmonary circulation. The conversion of angiotensin I to angiotensin II and the inactivation of bradykinin was thought to be mediated by the same enzyme.

In 1970, using Bradykin Potentiatin Factor (BPF) provided by Sergio Ferreira, Ng and Vane found that the conversion of angiotensin I to angiotensin II was inhibited during its passage through the pulmonary circulation. BPF was later found to be a peptide in the pit viper (Bothrops jararaca) venom which was a “collected-product inhibitor” of the converting enzyme. Captopril was developed from this peptide after it was found via QSAR-based modification that the terminal sulfhydryl moiety of the peptide provided a high potency of ACE inhibition.

Captopril gained FDA approval in June 1981. The drug went generic in the U.S. in February 1996 as a result of the end of market exclusivity for Bristol-Myers Squibb.

Limitations of captopril

The adverse drug reaction (ADR) profile of captopril is similar to other ACE inhibitors, with cough being the most common ADR (Rossi, 2006). However, captopril is also commonly associated with rash and taste disturbances (metallic or loss of taste), which are attributed to the unique sulfhydryl moiety (Atkinson & Robertson, 1979).

Captopril also has a relatively poor pharmacokinetic profile. The short half-life necessitates 2–3 times daily dosing, which may reduce patient compliance.

Subsequent ACE inhibitors

The adverse effect and pharmacokinetic limitations of captopril stimulated the development enalapril and subsequent ACE inhibitors. These were specifically designed to lack the sulfhydryl moiety believed to be responsible for rash and taste disturbance (Patchett et al., 1980). Most subsequent ACE inhibitors are given as prodrugs, to improve oral bioavailability. All have a longer half-life and are given once or twice daily, which may improve patient compliance.

Cough is the most common long-term adverse drug reaction associated with captopril therapy, as it is with all the ACE inhibitors. Hypotension is also a possible adverse effect, if the dose is too high. Hyperkalemia is possible, due to ACE inhibition reducing aldosterone production. Captopril can also be the cause of glomerulonephritis.

References

1. Atkinson AB, Robertson JIS. Captopril in the treatment of hypertension and cardiac failure. Lancet 1979;2(8147):836–9. PMID 90928

2. Patchett AA, Harris E, Tristam EQ, et al. A new class of angiotensin-converting enzyme inhibitors. Nature 1980;288(5788):280–3. PMID 6253826

3. Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006.

4. Smith CG, Vane JR. The discovery of captopril. FASEB J 2003;17:788-9. Fulltext. PMID 12724335.

5. Ferreira SH and Vane JR: The disappearance of bradykinin and eledoisin in the circulation and vascular beds of the cat. Br. J. Pharm. Chemother.,1967,30, 417-424.