Clinical Pharmacology of the Angiotensin Receptor Antagonists

Domenic A. Sica, MD, Division of Clinical Pharmacology and Hypertension, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA.

In This Article

Bioavailability

The bioavailability of the individual AT1-RAs is quite variable (Table I).[11,12,13,14,15,16,17,18,19,20,21,22,23,24] Two of the AT1-RAs -- losartan and candesartan cilexitil -- are administered in a prodrug form, although technically speaking, losartan is an active compound, albeit one ultimately converted to a more potent E-3174 metabolite. The bioavailability of eprosartan is low (~13%), a phenomenon that is not due to high first-pass elimination.[14] Irbesartan demonstrates a bioavailability profile with an absorption range between 60% and 80% and has no food effect.[17,18] Losartan has a moderate bioavailability (~33%), with 14% of an administered dose transformed to the E-3174 metabolite.[19,20] Telmisartan appears to have a saturable first-pass effect for its absorption; thus, the higher the dose the greater the absolute bioavailability. Unfortunately, the most pertinent absorption characteristic of individual AT1-RAs, which is day-to-day variability in bioavailability, is not routinely reported.

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