Alun Bedding

Effect of Tadalafil on Cytochrome P450 3A4–mediated Clearance: Studies in Vitro and in Vivo

Tadalafil was examined in vitro and in vivo for its ability to affect human cytochrome P450 (CYP) 3A‐mediated metabolism.

Adaptive dose-response studies

Insufficient exploration of the dose-response is a shortcoming of clinical drug development, and failure to characterize dosing early is often cited as a key contributor to the high late-stage attrition rate currently faced by the industry. Adaptive methods, for example, make it feasible to design a proof-of-concept study as an adaptive dose-response trial. Efficient learning about the dose response earlier in development will ultimately reduce overall costs and provide better information on dose in the filing package. This article presents the Pharmaceutical Research and Manufacturers of America working groups main recommendations regarding adaptive dose-response studies. As background, traditional fixed and adaptive dose-response designs are briefly reviewed. Information on developing a Bayesian adaptive dose design and some monitoring and processing issues are also discussed.

Effects of tadalafil on myocardial blood flow in patients with coronary artery disease.

ObjectiveErectile dysfunction and coronary artery disease share similar risk factors. Although phosphodiesterase-5 inhibitors used to treat erectile dysfunction do not adversely affect hemodynamic parameters in patients with coronary artery disease, their effects on myocardial blood flow are unknown. MethodsIn a randomized, double-blind, crossover study we examined the effects of tadalafil, 20 mg, compared with placebo on myocardial blood flow in patients with stable coronary artery disease (n=7, 52–73 years old). After tadalafil or placebo, myocardial blood flow was measured with positron emission tomography (nine-segment model) at rest, during maximal coronary hyperemia with adenosine, and during increased myocardial work with dobutamine. Abnormal flow was defined as myocardial blood flow <75% of maximum perfusion during adenosine plus placebo (46 normal/17 abnormal segments dentified). ResultsCompared with placebo, tadalafil had no significant effect on global myocardial blood flow at rest, during adenosine infusion, or during dobutamine infusion. Similarly, in normal and abnormal segments, tadalafil versus placebo had no significant effect on resting myocardial blood flow or on adenosine-induced increases in myocardial blood flow. In normal segments, myocardial blood flow with dobutamine plus tadalafil was greater than that with dobutamine plus placebo (1.79±0.56 versus 1.56±0.37 ml/g per min, P<0.01), and in abnormal segments, there was a trend for tadalafil compared with placebo to increase myocardial blood flow during dobutamine infusion (1.46±0.44 versus 1.36±0.36 ml/g per min, P=0.7). ConclusionsTadalafil had no significant effect on global myocardial blood flow at rest, during adenosine infusion, or during dobutamine infusion. Compared with placebo, tadalafil significantly augmented myocardial blood flow during increased workload in normal regions, with a trend toward improving myocardial blood flow in poorly perfused regions.