The effect of nadolol on heart rate in hyperthyroidism. A controlled trial

Twenty hyperthyroid patients were randomly assigned in a double-blind fashion to receive either nadolol 80 mg/day or placebo for 2 weeks; all patients then took carbimazole as well from 2-6 weeks. Twenty-four hour Holter ECG recordings at 0, 2 and 6 weeks showed that nadolol reduced the mean maximum heart rate by 19.9% (P less than 0.0005) at 2 weeks and by 30.3% (P less than 0.0005) at 6 weeks compared to 5.2% (ns) and 18.3% (P less than 0.0005) in patients taking placebo. There was no alteration of the normal circadian variation of heart rate by nadolol. The minimum heart rate before therapy was significantly correlated with FT4 (r = 0.52) and with FT3 (r = 0.44). The percentage of time per hour during which the heart rate was greater than 100 was reduced by 79% at week 2 by nadolol compared to 22% in the placebo group. At the 6 week point the placebo group still had a tachycardia (mean maximum heart rate 101.6 beats/min +/- 15.2 SD) compared to the nadolol group (80.4 +/- 7.7). Nadolol did not cause excessive bradycardia. It is effective in the early management of hyperthyroidism and should be given for at least the first 4-6 weeks.