R-VERAPAMIL - PHARMACOKINETICS AND EFFECTS ON PR INTERVAL, BLOOD-PRESSURE AND HEART-RATE

1 This study in healthy normotensive male volunteers investigated the pharmacokinetics and the effects on electrocardiographic PR interval, blood pressure and heart rate of single oral doses of the single isome r R-verapamil (250, 500 and 1000 mg) in comparison to placebo and 240 mg racemic verapamil. 2 After 500 and 1000 mg R-verapamil there were s ignificant prolongations in PR interval, maximal at 1-2 h after dosing and coincident with peak plasma drug concentrations, but these were n ot significantly different from the maximum prolongation obtained with 240 mg racemic verapamil. 3 After 1000 mg R-verapamil there was a sig nificant hypotensive effect, particularly on standing. 4 Single doses of 500 and 1000 mg R-verapamil produced peak plasma drug concentration s in the range 1000-3000 ng ml-1. If this concentration range is appro priate for adjuvant cancer chemotherapy it can be predicted that simil ar steady state concentrations will occur with a dosage regimen of 300 mg 3 times daily.