Mechanistic Model for Blood Pressure and Heart Rate Changes Produced by Telmisartan in Human Beings.

Telmisartan, an angiotensin receptor blocker (ARB), is indicated for the treatment of essential hypertension. This study aimed to develop a mechanistic model of telmisartan drug effect in human beings using non-invasive markers. Data were acquired from a previous study where telmisartan 80mg was given once daily for 6days. Systolic (SBP) and diastolic blood pressure (DBP) and heart rate (HR) were measured before dosing for days 1-5 and serially after the last dose. Mean arterial pressure (MAP) and pulse pressure (PP) were calculated from SBP and DBP. Relationships between MAP, PP, HR and total peripheral resistance (TPR) were developed. Circadian variation was incorporated into PP and HR, and TPR was assumed to adjust itself in response to changes in PP and HR based on baroreflex mechanism. Drug effects were then described as lowering the set point of MAP through TPR with a physiological feedback effect stimulating HR and PP. Drug concentrations were described by a two-compartment disposition model with first-order absorption and lag time, and first-order elimination. Circadian variation was described by cosine functions, having periods of 12 and 24hr. A log-linear model was used to describe drug effect, with estimated drug effect parameter of 0.051/hr. Estimated fractional turnover rate of PP, HR and TPR was 11.2hr. The model successfully described the time courses of these cardiovascular variables. This work demonstrated the feasibility of using non-invasive cardiovascular measurements to derive a mechanistic model for telmisartan in human beings. The model may be suitable for other ARBs.