A clinical pharmacological assessment of doxazosin and enalapril in combination.

This study in 12 normotensive males investigated potential pharmacokinetic and pharmacodynamic interaction mechanisms resulting from the combination of enalapril and doxazosin. Blood pressure reductions were consistently greater with the combination but there was no evidence of a significant pharmacodynamic interaction (as determined by heart rate changes, renal function tests or by pressor responsiveness indices) and there was no evidence of a pharmacokinetic interaction with either drug. Responsiveness to each drug i.e. blood pressure reduction per unit drug concentration was not significantly altered in the combination regimen. In conclusion, these results suggest that the combination of enalapril and doxazosin produces a usefully additive hypotensive effect but there was no evidence of synergism i.e an effect which was more than additive.

A comparative assessment of amlodipine and felodipine ER: pharmacokinetic and pharmacodynamic indices.

This study investigated potential therapeutic differences between Amlodipine 5 mg and Felodipine ER 10 mg in 12 normotensive/borderline hypertensive subjects by comparison of the plasma drug concentration-time profiles and the blood pressure and heart rate responses. There was significantly less trough-to-peak variability in plasma drug concentrations with amlodipine with a ratio of 67%, compared to 37% for felodipine. Correspondingly there was less variability with amlodipine in the blood pressure reductions across the dosage interval. Overall, amlodipine displayed a more consistent hypotensive effect across 24 hours and lower blood pressure values at trough, i.e. 24 hours post-dose.