Drugs that interact with levothyroxine: an observational study from the Thyroid Epidemiology, Audit and Research Study (TEARS)
Savannah A Irving, Thenmalar Valdiveloo, Graham P Leese
The difficult patient: drug interaction and the influence of concomitant diseases on the treatment of hypothyroidism
Laura S. Ward
PatientsThe study population was Tayside residents prescribed levothyroxine on at least three occasions, within a six-month period, prior to the start of a study drug. Individuals acted as their own controls pre- and postinitiation of study drug. Overall, 10 999 patients (mean age 58 years, 82% female) being treated with thyroxine were included in the study.
MeasurementsChanges in TSH following initiation of study drug.
ResultsIron, calcium, proton pump inhibitors and oestrogen all increased serum TSH concentration: an increase of 0.22 mU/l, 0.27 mU/l, 0.12 mU/l, and 0.08 mU/l, respectively. For these four study drugs, there was a clinically significant increase of over 5 mU/l in serum TSH, in 7.5%, 4.4%, 5.6% and 4.3% patients, respectively. There was a decrease of 0.17 mU/l in the TSH concentration for those patients on statins. The TSH decreased by 5 mU/l in 3.7% of patients. There was no effect with H2 receptor antagonists or glucocorticoids.
ConclusionThis large population-based study demonstrates significant interaction between levothyroxine and iron, calcium, proton pump inhibitors, statins and oestrogens. These drugs may reduce the effectiveness of levothyroxine, and patients' TSH concentrations should be carefully monitored.
- TEARS - The Thyroid Epidemiology, Audit, and Research Study:
- Thyroid dysfunction in the general population
- Thyroid testing in pregnant women with thyroid dysfunction
- The natural history of endogenous subclinical hyperthyroidism
- Wisselwerkingen levothyroxine, andere medicijnen en voedingsmiddelen
- Chronische inflammatoire darmziekten
- Bijsluiters medicijnen
- Praktische tips voor het slikken van levothyroxine
- Effects of the environment, chemicals and drugs on thyroid function
- Levothyroxine innemen met koffie: geen goed idee
- Effects of grapefruit juice on the absorption of levothyroxine