A study of long acting propranolol in the early management of hyperthyroidism.

1 The effects of propranolol in its long acting formulation, 160 mg long acting (LA) propranolol, were assessed in a double-blind, controlled study of 20 hyperthyroid patients. Further observations with the addition of carbimazole were also made. 2 LA propranolol effectively improved the clinical manifestations of hyperthyroidism. 3 Plasma concentrations of total T4 and rT3 were increased, but total T3 did not fall significantly during LA propranolol treatment. 4 LA propranolol with carbimazole produced a greater reduction in the clinical indices of hyperthyroidism than carbimazole alone. 5 Total serum T4 and rT3 concentrations remained elevated with LA propranolol and carbimazole compared to carbimazole alone. 6 Carbimazole therapy for 2 weeks did not alter the mean plasma propranolol concentration. 7 We concluded that LA propranolol is effective in hyperthyroidism and its effects are similar to those reported by other workers with conventional propranolol. The clinical and biochemical effects of LA propranolol continue during concomitant carbimazole therapy.