Clinical pharmacokinetics of beta-adrenoceptor blocking drugs in thyroid disease.

Abstract

β-Adrenoceptor blocking drugs (β-blockers) have an established place in the management of patients with thyroid disease. Thyroid hormones, however, markedly alter hepatic, renal and cardiovascular function and thus may significantly influence drug disposition. In hyperthyroidism the clearance of propranolol following intravenous administration is increased by approximately 50%, an effect that may be attributed to the marked increase in liver blood flow that occurs in this condition. On the other hand, the increased clearance of propranolol during long term oral therapy is presumably due to increased hepatic drug metabolising enzyme activity. However, following single oral doses the clearance of propranolol has been reported both to be unchanged and increased in hyperthyroid patients. Both during single dose and long term therapy the elimination half-life of propranolol is unaltered, in part due to an increased apparent volume of distribution. The degree of plasma protein binding of propranolol appears to be slightly reduced in the hyperthyroid state.