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Disposition of captopril in normal subjects
Clinical Pharmacology and Therapeutics
|May 1, 1980
Summary
Captopril, an ACE inhibitor, is rapidly absorbed, with peak blood levels reached in about an hour. Most of the drug is eliminated via urine, primarily as captopril and its metabolites.
Area of Science:
- Pharmacology
- Drug Metabolism
- Clinical Pharmacy
Background:
- Captopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat hypertension.
- Understanding the pharmacokinetic profile of captopril is crucial for optimizing its therapeutic use.
Purpose of the Study:
- To investigate the absorption, distribution, metabolism, and excretion (ADME) of captopril in healthy male subjects.
- To characterize the disposition of a single oral dose of 35S-labeled captopril.
Main Methods:
- 10 healthy male subjects received a single 100-mg tablet of 35S-labeled captopril.
- Blood, urine, and fecal samples were collected over time to measure radioactivity and drug concentrations.
- Pharmacokinetic parameters including Tmax and Cmax were determined.
Main Results:
- Captopril was rapidly absorbed, with peak plasma concentrations of unchanged drug and total radioactivity observed around 1 hour post-dose.
- Elimination half-life of unchanged captopril could not be determined due to plot linearity.
- Approximately 68% of the radioactive dose was recovered in urine and 18% in feces within 5 days.
- In the first 24-hour urine, captopril accounted for 38% of the dose, with metabolites comprising the remainder.
Conclusions:
- Captopril undergoes rapid absorption and significant renal excretion.
- The primary circulating forms are unchanged captopril and its disulfide metabolite.
- Further characterization of unidentified polar metabolites is warranted.