No enhanced elimination of propranolol in patients with hyperthyroidism

Propranolol, a widely used beta-adrenergic receptor blocking drug extracted mostly by the liver, plays an important role in the various aspects of managment of hyperthyroidism. If the elimination of this drug is enhanced in thyrotoxic patients, one may consider necessary a modification of the dosage regimien when treating patients with this dysfunction. We examined the disposition profiles of propranolol in four patients with hyperthyroidism before and after their thyroid states became euthyroid and compared them to those of the seven control subjects. The data indicated that the values (mean +/- SEM) of half-life (3.34 +/- 0.81 hr) and systemic availability estimated (28.2 +/- 3.5%) in the hyperthyroid state were comparable to those in the euthyroid state (2.98 +/- 0.32 hr and 29.2 +/- 5.1%) and these in the control subjects (3.20 +/- 0.32 hr and 29.0 +/- 4.0%). Although our observations were obtained from a small number of subjects, there appears to be no considerable difference in propranolol elimination from the plasma of hyperthyroid and euthyroid states or healthy subjects, and therefore adjustment of the dosage regimen seems unwarranted. Adjustment of propranolol therapy based on individual plasma levels might be useful in thyrotoxic patients who respond inadequately until additional data relating more precisely to propranolol disposition becomes available.