Comparative Pharmacology
Head-to-head clinical analysis: PROPYLTHIOURACIL versus THYRO BLOCK.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PROPYLTHIOURACIL versus THYRO BLOCK.
PROPYLTHIOURACIL vs THYRO-BLOCK
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Propylthiouracil (PTU) inhibits thyroid peroxidase, thereby blocking the synthesis of thyroid hormones. It also inhibits the peripheral conversion of thyroxine (T4) to triiodothyronine (T3).
THYRO-BLOCK (potassium iodide) inhibits thyroid hormone synthesis and release by blocking the oxidation of iodide to iodine, thereby preventing the incorporation of iodine into thyroglobulin. It also reduces the vascularity of the thyroid gland.
Oral, 300-600 mg/day in 3 divided doses until euthyroid; then 50-150 mg/day as maintenance.
Oral, 120 mg every 12 hours (total daily dose 240 mg) starting 24 hours before exposure to radioactive iodine and continuing for 5–10 days as directed.
None Documented
None Documented
Clinical Note
moderatePropylthiouracil + Clozapine
"The risk or severity of adverse effects can be increased when Propylthiouracil is combined with Clozapine."
Clinical Note
moderateWarfarin + Propylthiouracil
"Warfarin may decrease the anticoagulant activities of Propylthiouracil."
Clinical Note
moderatePhenprocoumon + Propylthiouracil
"Phenprocoumon may decrease the anticoagulant activities of Propylthiouracil."
Clinical Note
moderatePhenindione + Propylthiouracil
Terminal elimination half-life is 1-2 hours in euthyroid patients, but may be prolonged to 2-5 hours in hyperthyroid patients due to altered metabolism and thyroid status. Clinical effect persists longer than half-life due to inhibition of thyroid peroxidase.
Terminal elimination half-life is approximately 36 hours (range 24-48 hours) in euthyroid patients; prolonged in hyperthyroid patients due to increased thyroid hormone binding and reduced clearance.
Primarily renal (approximately 35% as unchanged drug within 24 hours; remainder as inactive metabolites). Minor biliary/fecal elimination (<5%).
Primarily renal excretion of unchanged drug (80-90% of absorbed dose) via glomerular filtration; minimal biliary/fecal elimination (<5%).
Category D/X
Category C
Antithyroid Agent
Antithyroid Agent
"Phenindione may decrease the anticoagulant activities of Propylthiouracil."