Variable Plasma Propranolol Levels in Thyrotoxicosis

PROPRANOLOL has been widely used in the preparation of thyrotoxic patients for operation,^{1 2 3} in the treatment of thyroid storm,^{4 5} and as adjunct⁶ or sole⁷ therapy in the symptomatic management of hyperthyroid subjects. Several observers, however, have noted that the degree of relief of hyperthyroid symptoms provided by propranolol alone is not sufficient in many patients.^{8 9 10} Furthermore, propranolol in conventional doses does not necessarily prevent thyroid storm.¹¹ Since plasma propranolol concentrations were not determined in any of these studies, the apparent therapeutic failures may have been the result of inadequate drug levels. We therefore investigated propranolol pharmacokinetics in thyrotoxic subjects. We.