In a placebo controlled exercise protocol using healthy volunteers the effects of
nadolol 80 mg and 160 mg orally and of
nadolol 80 mg during treatment with
nifedipine 20 mg 8 hourly were compared. Resting systolic and diastolic blood pressures were reduced by both
nifedipine (p less than 0.05) and
nadolol (p less than 0.01) acting alone. An unexpected finding was that
nifedipine alone significantly inhibited exercise
tachycardia (p less than 0.01) (8 to 12 h post dose). Predictably both doses of
nadolol produced significant reduction in exercise
tachycardia which was still apparent at 24 h. There was a linear relationship between log10 plasma
nadolol concentration and reduction in exercise heart rate. The combined inhibitory effects of
nifedipine and
nadolol 80 mg on exercise heart rate showed partial additivity but did not summate. There was no pharmacokinetic interaction between the 2 drugs. The inhibition of exercise
tachycardia by
nifedipine, not previously documented, is consistent with an effect of the
drug on the sinus node, as has been reported in in-vitro studies, and may contribute to the drugs efficacy in angina.