MajorThyroid hormones×Proton pump inhibitors
Updated · Methodology
Mechanism
Levothyroxine needs gastric acidity to dissolve before it can be absorbed. Omeprazole raises stomach pH and the dissolved fraction drops; the AEMPS label names proton pump inhibitors alongside calcium and iron. Unlike chelation, spacing the doses does not solve this one: pH stays high all day.
Symptoms
TSH rises after omeprazole is started and does not return to baseline even when the hormone timing changes. In atrophic gastritis or Helicobacter the drop is larger.
Management
If the inhibitor is staying, check TSH 6–8 weeks after starting it and adjust the levothyroxine dose on the result. When omeprazole stops, repeat the check: absorption recovers and the adjusted dose may now be too high. Also review whether the inhibitor is still needed, since many courses run on without a current indication.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
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
- AEMPS: Ficha técnica Levotiroxina Aristo 100 microgramos comprimidos EFG (2023)– AEMPS, CIMA, nº registro 84484, sección 4.5
- AEMPS: Ficha técnica Esomeprazol Cinfa 20 mg cápsulas gastrorresistentes EFG (2024)– AEMPS, CIMA, nº registro 82921, secciones 4.4 y 4.8