Telmisartan is a potent, long-lasting, nonpeptide antagonist of the angiotensin II type-1 (AT 1 ) receptor that is indicated for the treatment of essential hypertension. It selectively and insurmountably inhibits stimulation of the AT 1 receptor by angiotensin II without affecting other receptor systems involved in cardiovascular regulation. Very high lipophilicity, a unique feature of telmisartan, coupled with a high volume of distribution, indicate that the compound offers the clinically important advantage of good tissue penetration. Telmisartan is not a prodrug and has a longer terminal elimination half-life than other commercially available sartans (~24 h), making it suitable for once-daily dosing. The compound is not metabolized by cytochrome P450 isoenzymes and has a low risk for P450-based drug interactions. In animal models, telmisartan exhibits pronounced cardioand reno-protective effects in animals with severe, essential hypertension. In clinical studies, telmisartan shows comparable antihypertensive activity to members of other major antihypertensive classes, such as ACE inhibitors, beta blockers and calcium antagonists. These trials have confirmed the placebo-like safety and tolerability of telmisartan in hypertensive patients. Based on these data, telmisartan offers advantages over other sartans and represents an important new treatment option for hypertension.

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Preclinical toxicity studies in animals with species-specific recombinant DNA products have now been performed for several years. An interim statement on the significance of these animal tests and their ability to predict adverse effects in humans therefore appears indicated, with the aim of deducing future testing strategies. The experience accumulated so far shows that the animal models have failed to predict adverse effects subsequently observed in man. Immunogenicity of these proteins further restricted the usefulness of standard toxicity tests. There is also increasing evidence that animal tests on the toxic potential of impurities contained in the products are markedly inferior in sensitivity to analytical and quality control methods. Thus, modified testing programs are proposed to demonstrate safety rather than target organ toxicity using rodents and small non-rodent species and restricted dosing; furthermore the study duration should be limited by the detection of immunogenic responses.

A joint study was undertaken in three testing facilities to evaluate cumulative background data of Himalayan rabbits.All litters were derived from control does. The conception rate was high (84.0-95.1%) but the average numbers of corpora lutea (7.9-8.7), implantation sites (6.5-7.5) and viable fetuses (5.8-6.9) were somewhat lower than that of most other strains of rabbit.Altogether 90 malfomed fetuses (1.12 %) and 425 fetuses with variations (5.270) occurred among 8, 060 virable fetuses.

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