Telmisartan is a new angiotensin receptor antagonist possessing potent, selective, and insurmountable inhibitory activity specific to the angiotensin II type 1 (AT 1 ) receptor. The current study was performed to determine the inhibition of the angiotensin II pressor response by telmisartan in 48 healthy volunteers challenged with hypertension-inducing doses of i.v. angiotensin II. Subjects were challenged with this dose of angiotensin II at intervals between 0.25 and 48 h after double-blind single-dose oral administration of telmisartan 20 mg (n = 12), 40 mg (n = 12), or 80 mg (n = 12) or placebo (n = 12) in parallel groups. Diastolic and systolic blood pressure and pulse rate were recorded continuously using a servophotoplethysmograph. Urine samples were collected during the study for urinalysis. Tolerability of telmisartan, in comparison with placebo, was also monitored throughout the study. Telmisartan 20-80 mg dose dependently inhibited the increase in diastolic and systolic blood pressure induced by angiotensin II. Telmisartan 40 mg produced 80.1% maximum inhibition, and with 80 mg 89.6% maximum inhibition of diastolic blood pressure was achieved. Inhibition was apparent after 0.3-1.1 h and was still observed 48 h after administration for all telmisartan doses. The inhibitory effect of telmisartan 20, 40, and 80 mg, 48 h after dosing was significantly greater than that of placebo. A > 25% inhibition of the angiotensin II response on diastolic blood pressure was detected until 26.9, 35.4, and 40.5 h, respectively, after telmisartan 20 mg, 40 mg, and 80 mg. Anti-clockwise hysteresis was observed, indicating a delay and longer persistence of effect than to be expected from the plasma concentration-time course. The slow dissociation of telmisartan from the receptor probably contributed to this hysteresis. The incidence of adverse events was comparable in telmisartan-and placebo-treated subjects and was not dose dependent. In conclusion, telmisartan 40 mg provides rapid-onset, well-tolerated, and near-maximal inhibition of angiotensin II-induced hypertension, with maintenance of the inhibitory effect for 48 h.

The pharmacokinetics and safety of telmisartan were assessed in subjects with hepatic impairment in a single‐center, open‐label study. Single oral doses of telmisartan 20 mg and 120 mg, separated by a washout period of 14 days, were given to 12 hepatically impaired subjects and 12 healthy subjects. In 5 hepatically impaired subjects who received both oral doses, a single IV infusion of telmisartan 120 mg was later administered. After oral dosing, the pharmacokinetic profile of telmisartan was characterized by rapid absorption and disposition kinetics and a slow terminal elimination phase with mean half‐lives of 27 to 42 hours. The maximum plasma concentration and area under the telmisartan plasma concentration‐time curve (AUC0‐∞) increased in hepatically impaired subjects compared with healthy volunteers 6.4‐fold and 2.7‐fold, respectively, for telmisartan 20 mg and 3.2‐fold and 3.1‐fold, respectively, for telmisartan 120 mg. Maximum plasma concentrations and AUC0‐∞ after IV infusion were markedly elevated compared with values obtained from other studies conducted in healthy volunteers. Hepatic impairment resulted in an apparent increase in the absolute bioavailability of telmisartan, and total clearance following oral and IV administration was significantly reduced compared with healthy volunteers. Plasma protein binding of telmisartan was ≥ 99.5% in hepatically impaired and healthy subjects and was not changed when compared to healthy subjects. Oral and IV telmisartan were well tolerated in both the hepatically impaired and the healthy; headache was the most common potentially telmisartan‐related adverse event. Changes in vital signs and clinical laboratory parameters were transient and of no clinical relevance. The good tolerability of telmisartan in hepatically impaired patients demonstrated in this study, the proven sustained blood pressure control in hypertensive patients, and the increased exposure in patients with hepatic dysfunction suggest that effective treatment of hypertensive patients with impaired hepatic function would be achieved even with the lowest dose of telmisartan available. The increased bioavailability of telmisartan suggests that lower doses of telmisartan should be considered when the drug is administered to patients with hepatic impairment.

The effects of multiple‐dose telmisartan on the steady‐state pharmacodynamics and pharmacokinetics of warfarin were assessed in 12 healthy young males in an open‐label, single‐period study conducted over 30 days. Subjects received loading doses of oral once‐daily warfarin on days 1 to 5, which were individually adjusted at days 6 and/or 9 to attain stable predose prothrombin time values (INRpre) of between 1.2 and 1.8 by the end of medication phase 1 (day 14). From days 15 to 24 (medication phase 2), subjects received oral once‐daily telmisartan 120 mg in addition to individualized oral doses of once‐daily warfarin. On days 25 to 31 (medication phase 3), oral once‐daily warfarin was again administered alone at individualized doses. Under steady‐state conditions, INRpre remained unchanged during medication phases 1, 2, and 3. The difference between phases 1 and 3 was −0.04 (95% confidence interval [CI]: −0.7 to 0.10) and between phases 2 and 1 was 0.03 (95% CI: −0.11 to 0.10). Mean trough plasma warfarin concentrations (Cpre) were stable during medication with warfarin alone but showed a small, although statistically significant, decrease during the combined‐medication phase. The point estimate of the ratio of phase 2/phase 1 was 0.89 (95% CI: 0.84 to 0.95). The decrease in Cpre did not result in decreased anticoagulation. This suggests that the extent of pharmacokinetic interaction between telmisartan and warfarin is limited, and since telmisartan had no effect on INRpre and the concomitant medication was well tolerated, there is no evidence for a clinically relevant interaction between telmisartan and warfarin.

A multiple‐dose, open‐label, two‐period, crossover randomized study was conducted in 12 healthy male volunteers to investigate the effect of multiple‐dose telmisartan on the steady‐state pharmacokinetics of digoxin. On day 1 of a 7‐day medication period, subjects received a loading dose of digoxin 0.5 mg in the morning, followed by an evening dose of digoxin 0.25 mg, either alone or together with telmisartan 120 mg administered in the morning. On the subsequent 6 days, either digoxin 0.25 mg or digoxin 0.25 mg together with telmisartan 120 mg was administered once daily in the morning. Each 7‐day medication period was separated by a washout period of ≥ 14 days. A steady‐state plasma concentration‐time profile was assessed for digoxin during each period and for telmisartan during the period with the combined treatment. Multiple‐dose telmisartan administered with digoxin resulted in higher serum digoxin concentrations than those observed after digoxin given alone. Geometric mean AUC144–168, Cmax, and Cmin values for digoxin when given in combination with telmisartan were higher by 22%, 50%, and 13%, respectively, compared with values when given alone. However, the 90% confidence interval for the geometric mean of Cmin was within the predefined 80% to 125% range of no interaction. During combination medication, digoxin tmax was shorter and Cmax/AUC144–168 increased, suggesting that the rise in digoxin Cmax may be due to more rapid drug absorption. Study medications were well tolerated, with the incidence, nature, and intensity of adverse events being similar during both medication periods. Also, no changes in vital signs or clinical laboratory tests were observed during the study. Although there was some evidence for a pharmacokinetic interaction between digoxin and telmisartan found in this study, the safety and tolerability of digoxin were unaffected by concurrent administration of telmisartan in the study population. Since any symptoms of overdose are related only to steady state and not peak concentrations and due to the fact that there was a lack of effect on serum trough levels of digoxin in this study, it is unlikely that the findings have any clinical relevance. The magnitude of increase in digoxin concentrations is comparable with increases observed with administration of calcium antagonists, carvedilol, ACE inhibitors such as captopril, and antiarrhythmic drugs such as amiodarone, quinidine, and propafenone. Monitoring of serum digoxin concentrations should be considered when patients first receive telmisartan and in the event of any changes in telmisartan dose.

This open‐label, crossover study was performed to establish if there is evidence for interaction between telmisartan, an angiotensin II antagonist, and amlodipine, a class II (dihydropyridine) calcium channel antagonist, on the basis of pharmacokinetics and safety. In a two‐way crossover trial, 12 healthy Caucasian males were randomized to receive once daily for 9 days oral amlodipine 10 mg with or without oral telmisartan 120 mg. After a washout period of ≥ 13 days, the subjects were switched to the other medication regimen. The geometric means of the primary pharmacokinetic parameters at steady state (day 9) for amlodipine when given alone were the following: maximum plasma concentration (Cmax) 17.7 ng/mL, area under the plasma concentration‐time curve (AUC) 331 ng•h/mL, and renal clearance 39.5 mL/min, with 8% of the total amlodipine dose being excreted. When concomitant telmisartan was given, the respective values were 18.7 ng/mL, 352 ng•h/mL, and 43.0 mL/min, with 9.4% of the total amlodipine dose being excreted renally The limits of the 90% confidence intervals (CIs) for the ratios of these steady‐state parameters were 0.97 to 1.14 for Cmax and 0.98 to 1.16 for AUC; both were within the predefined reference range (0.8 to 1.25) for bioequivalence. The high intersubject variability in urinary amlodipine excretion resulted in bioequivalence not being demonstrated for renal clearance. Adverse effects were few, mild to moderate in intensity, and transient whether amlodipine was given alone or with telmisartan. Vital signs, except for blood pressure, and clinical laboratory values were unaffected by either medication. The findings of this study show that concomitant telmisartan and amlodipine may be administered as there is no clinically significant variation in primary pharmacokinetic parameters of amlodipine in the presence of telmisartan, and the safety of the combination is comparable to that of amlodipine alone.