Propylthiouracil disposition in older hypothyroid patients.

The pharmacokinetic disposition of propylthiouracil (PTU) after a single oral dose was studied in 6 severely hypothyroid patients. Severity of disease, as indicated by thyroid-stimulating hormone concentration, was inversely related to plasma clearance of PTU. There were trends to increased apparent volume of distribution and plasma half-life for PTU as a function of age. The large apparent volume of distribution for PTU in these patients compared to euthyroid and hyperthyroid subjects, after a single drug dose, suggests that hypothyroidism as well as chronic drug ingestion must be considered as possible factors mediating this change.