The pharmacokinetic-pharmacodynamic model of telmisartan and hydrochlorothiazide on blood pressure and plasma potassium after long-term administration in spontaneously hypertensive rats.

A pharmacokinetic-pharmacodynamic model was developed to describe the time course of blood pressure and plasma potassium after long-term telmisartan and/or hydrochlorothiazide administration in spontaneously hypertensive rats. The spontaneously hypertensive rats were administered once daily for 6 weeks. The drug concentration, blood pressure and plasma potassium were monitored for several points. The time courses of blood pressure and plasma potassium were described by indirect response pharmacokinetic-pharmacodynamic model. The synergistic antihypertensive pharmacodynamic interaction between telmisartan and hydrochlorothiazide was observed, which was simulated by the inhibitory function of telmisartan and stimulatory function of hydrochlorothiazide after co-administration of the two drugs. For plasma potassium, when hydrochlorothiazide administrated alone, the plasma potassium reached to a low steady-state level at 4.64 mmol/L for 6 weeks. The plasma potassium increased to a steady-state level at 4.84 mmol/L after co-administration of telmisartan. The time courses of plasma potassium were successfully characterized by indirect response pharmacokinetic-pharmacodynamic model after long-term administration of telmisartan and/or hydrochlorothiazide. The model captured turnovers of blood pressure and plasma potassium in the different time phases and dose conditions.