Pharmacokinetics and clinical effects of atenolol in therapy of hyperthyroidism.

The pharmacokinetics of atenolol and the effect of the drug on the clinical and laboratory features of hyperthyroidism were studied in 23 patients with hyperthyroidism. In the hyperthyroid state, the time to peak plasma concentration (Tmax) occurred significantly earlier, the elimination half-life was significantly shorter, and the areas under the curve were also significantly less compared to the euthyroid state, but there was no significant difference in peak plasma concentrations (Cmax) between these states. Administration of atenolol once daily resulted in marked clinical improvement in 2 to 4 weeks. The clinical index of thyrotoxic symptoms and signs decreased from 23.2 +/- 10.8 to 8.4 +/- 5.3 (p less than 0.005). Pulse similarly decreased significantly from 93.9 +/- 15.7 to 77.8 +/- 10.5. In contrast to the marked clinical improvement, there was no change in any of the serum concentrations of thyroid hormones T4, free T4, T3 and free T3 at the time of maximal clinical effect compared to pretreatment values. These data show that the beneficial effect of atenolol in hyperthyroidism is not due to changes in thyroid hormone metabolism.