Cardioselectivity and Partial Agonist Activity in the Antianginal Efficacy of the β-Adrenoceptor Antagonists

Summary

An open randomised crossover study (20 patients) was performed to compare the efficacy in stable effort angina of atenolol 100mg once a day, and pindolol 5mg thrice daily.

After a placebo run- in period the 2 treatments were given for 6 weeks each. The number of anginal attacks and consumption of glyceryl trinitrate tablets were noted and side effects recorded. During a multistage treadmill test, measurements were made of exercise tolerance, systolic blood pressure, heart rate, HR × systolic BP product and S- T segment displacement.

Both drugs substantially reduced the number of anginal attacks[from a mean of 7.6 ± 1.2 per week in the placebo period to 1.8 ± 0.6 (atenolol) and 2.9 ± 0.5 (pindolol) at the sixth week of treatment] and glyceryl trinitrate consumption. Atenolol was significantly more effective than pindolol in reducing the number of anginal attacks at 3 and 6 weeks and glyceryl trinitrate tablets taken at 3 weeks.

The mean walking time on atenolol (13.38) ± 0.98 min) was significantly (p < 0.01) longer than with pindolol (11.88 ± 0.91 min). Both drugs tended to lower the heart rate after 3 weeks of treatment; after 6 weeks atenolol further lowered heart rate, but with pindolol heart rate increased to almost run- in values. Treatment length also influenced the effect of the 2 drugs in a similar manner when other measurements were made and this could be due to the different properties [partial agonist activity (PAA) and cardioselectivity] of pindolol and atenolol. In terms of global clinical assessment, atenolol (100 mg/day) proved to be more effective.