Moderate
Levothyroxine sodium × Omeprazole
Thyroid hormones×Proton pump inhibitors
Mechanism
Proton pump inhibitors raise gastric pH, reducing levothyroxine absorption. TSH may rise 2–4 weeks after starting omeprazole.
Symptoms
Return of hypothyroidism: fatigue, weight gain, cold intolerance, dry skin, low mood. In thyroid cancer (TSH suppression needed), loss of control.
Management
Take levothyroxine 30–60 minutes before food and omeprazole. Check TSH 6–8 weeks after starting or stopping omeprazole. If TSH rises, increase levothyroxine by 12.5–25 mcg.
Sources
- ATA: Guidelines for the Treatment of Hypothyroidism (2014)– Thyroid 2014;24(12):1670–1751
- Lexicomp: Lexicomp Drug Interactions (2024)– Wolters Kluwer Clinical Drug Information, Inc. Lexi-Interact Online, 2024
- Pharmaceutical Press: Stockley's Drug Interactions, 12th edition (2024)– Preston CL (ed.). Stockley's Drug Interactions. 12th ed. London: Pharmaceutical Press; 2024