Biol. Pharm. Bull. 28(12) 2235—2239 (2005)

angiotensin II type 1 (AT1) receptor antagonist have been widely used by patients with high blood pressure, kidney disease and heart failure. Telmisartan (BIBR 277) is the most recently marketed AT1 receptor antagonist. 2) Telmisartan lowers blood pressure though blockade of the renin-angiotensin-aldosterone system. The efficacy of telmisartan has been shown to be at least equivalent to that of many other commonly prescribed antihypertensive agents, including enalapril, lisinopril, amlodipine, atenolol and losartan. Telmisartan has demonstrated a safety profile similar to that of placebo with respect to the incidence of adverse events and abnormalities in standard laboratory tests. Furthermore, unlike angiotensin-converting enzyme (ACE) inhibitors, telmisartan has not been associated with cough, a characteristic shared with other members of the class. Recent studies have shown that multiple transporters are expressed in the gastrointestinal tract and play an important role in the secretion and absorption of pharmacologically active compounds. It is possible that drug–drug interactions involving transporters directly affect the therapeutic safety and efficacy of many important drugs. In clinical practice, telmisartan is coadministered with many kinds of drugs. It has been reported that several cardiovascular drugs, including digoxin, ACE inhibitors and calcium antagonists, interact with intestinal transporters. However, little is known about the contribution of transporters to the intestinal transport of telmisartan. The human colon adenocarcinoma cell line Caco-2 has been used as a model in which to study intestinal absorption or secretion of various drugs. This cell line spontaneously differentiates in culture into polarized cell monolayers with many enterocyte-like properties of transporting epithelia. Caco-2 cells retain various transporters expressed in the intestine. Using this model, a number of studies have been performed to characterize the intestinal transport mechanism. The present study was carried out to elucidate the transport mechanism of telmisartan across intestinal epithelial cells using Caco-2 cells.