Clinical pharmacokinetics of ramipril

Ramipril is a long-acting nonsulfhydryl angiotensin converting enzyme (ACE) inhibitor introduced for clinical use about a decade ago. Ramipril is a prodrug that undergoes de-esterification in the liver to form ramiprilat, its active metabolite. Ramipril rapidly distributes to all tissues, with the liver, kidneys and lungs showing markedly higher concentrations of the drug than the blood. After absorption from the gastrointestinal tract, rapid hydrolysis of ramipril occurs in the liver. In the therapeutic concentration range, protein binding of ramipril and ramiprilat is 73 and 56%, respectively. Ramiprilat binds to ACE with high affinity at concentrations similar to that of the enzyme and establishes equilibrium slowly. Although ramipril is metabolised by hepatic and renal mechanisms to both a glucuronate conjugate and a diketopiperazine derivative, most of the drug is excreted in the urine as ramiprilat and the glucuronate conjugate of ramiprilat. Elimination from the body is characterised by a relatively rapid initial phase with a half-life of 7 hours and a late phase with a half-life of about 120 hours. No clinically significant pharmacokinetic interactions between ramipril and other drugs have been reported. The drug has been generally well tolerated with the most prevalent adverse effects being dizziness (3.4%), headache (3.2%), weakness (1.9%) and nausea (1.7%). Ramipril is an effective and well tolerated drug for the treatment of hypertension and congestive heart failure in all patients, including those with renal or hepatic dysfunction, and the elderly.