Association of cigarette smoking with steady-state plasma concentration of irbesartan in male Chinese with hypertension.

Previous studies suggested that cigarette smoking, being highly prevalent in many countries, is an important environmental factor that contributes to interindividual variations in response to certain medications. To investigate the possible interactions between irbesartan (a commonly used angiotensin II type 1 receptor antagonist) and cigarette smoking, we recruited 491 male patients with essential hypertension from two rural districts of China. All subjects were treated with irbesartan (150 mg/day) for 28 days, and the steady-state plasma concentrations of irbesartan 24 h after the dose of day 27 (the trough level) and 6 h after the dose of day 28 were determined using prevalidated high-performance liquid chromatography (HPLC)-fluorescence method. Multiple linear regression was used to analyze the effect of smoking on the steady-state plasma concentrations of irbesartan, with potential confounding factors adjusted. The results showed that current smokers had significantly higher average steady-state trough plasma level of irbesartan than that of the nonsmokers and former smokers. The finding was still valid when subjects from the two different districts were separately analyzed. The stratified analysis according to age suggested that the effect of increasing irbesartan concentration by current cigarette smoking in the elderly patients was stronger than that in adults. The metabolism of irbesartan in current smokers was slower compared to that in nonsmokers and former smokers. In summary, the present study showed significant associations between current cigarette smoking and an increased steady-state trough plasma concentration of irbesartan in a male Chinese population with hypertension. The metabolic rate of irbesartan in current smokers was slower than those in nonsmokers and former smokers.