Benazepril’s active form has an effective half-life of 10 to 11 hours, meaning it takes roughly 2 to 2.5 days (about 50 to 55 hours) for the drug to be essentially cleared from your body after your last dose. That timeline applies to most adults regardless of age, though kidney function can slow things down significantly.
How Benazepril Is Processed in Your Body
Benazepril itself is actually a prodrug. After you swallow it, your liver converts it into its active form, called benazeprilat, which is the compound that lowers blood pressure. This conversion happens quickly, and benazeprilat is what stays in your system doing the work.
The effective half-life of benazeprilat is 10 to 11 hours. A “half-life” is the time it takes for the amount of drug in your blood to drop by half. Pharmacologists generally consider a drug fully eliminated after about five half-lives, because by that point less than 3% of the original dose remains. For benazeprilat, five half-lives works out to roughly 50 to 55 hours, or just over two days.
When you take benazepril daily, it reaches a consistent level in your blood (called steady state) after just 2 or 3 doses. That also means if you stop taking it, the drug doesn’t linger for weeks. Within two to three days, the vast majority is gone.
How the Drug Leaves Your Body
Benazeprilat is eliminated predominantly through the kidneys. After a dose, about 20% is excreted in urine as benazeprilat, with additional smaller amounts leaving as related breakdown products (about 4% and 8% as two different metabolites). Only trace amounts of the original, unconverted benazepril show up in urine. A smaller portion is cleared through bile.
Because the kidneys handle most of the work, anything that affects kidney function can change how long the drug stays in your system. If your kidneys are impaired, clearance slows and the drug remains at higher levels for longer. Liver disease, on the other hand, does not meaningfully change how benazeprilat is processed. Age also has no significant effect on clearance.
How Long the Effects Last
Even though the drug takes about two days to fully leave your system, its blood pressure-lowering effect from a single dose persists for roughly 24 hours. Peak blood pressure reduction happens 2 to 4 hours after you take it, with the effect starting within the first hour. A single dose of 10 mg or more inhibits the enzyme that raises blood pressure (ACE) by at least 80% to 90% for a full 24 hours.
This is why benazepril is prescribed as a once-daily medication. The drug’s activity lines up well with a 24-hour dosing schedule, even though traces remain in your blood a bit longer than that.
Benazepril and Drug Testing
Benazepril is a blood pressure medication, not a controlled substance. It does not show up on standard drug screenings, which typically look for substances like opioids, amphetamines, and cannabinoids. There is no routine workplace or forensic test designed to detect ACE inhibitors like benazepril. If you need to disclose your medications for a medical procedure or specialized test, simply listing it on your medication history is sufficient.
Factors That Can Slow Clearance
For most people, the 50-to-55-hour clearance window is reliable. The two main variables worth knowing about:
- Kidney function: Since the kidneys are the primary route of elimination, reduced kidney function extends the time benazeprilat stays in your blood. People with significant kidney impairment may take noticeably longer to clear the drug.
- Dose: Higher doses mean more drug to eliminate, which can push the tail end of clearance slightly further out, though the half-life itself stays the same.
Notably, age and liver disease (including cirrhosis) do not meaningfully alter how quickly benazeprilat is cleared. This makes benazepril’s timeline fairly predictable for most adults.