Drug interactions between Gleevec and Synthroid
| Results for the following 2 drugs: |
|---|
| Gleevec (imatinib) |
| Synthroid (levothyroxine) |
Interactions between your selected drugs
levothyroxine ↔ imatinib
Applies to:Synthroid (levothyroxine) and Gleevec (imatinib)
ADJUST DOSE: Imatinib has been reported to induce clinical hypothyroidism in patients receiving levothyroxine. The exact mechanism is unknown but may involve stimulation of the non-deiodination clearance of T4 and T3 by imatinib. In 11 patients treated with imatinib for an average of six months, eight patients who had previously undergone total thyroidectomy and used levothyroxine developed symptoms of hypothyroidism, while the three patients with thyroid in situ remained clinically and biochemically euthyroid. On average, thyrotropin (TSH) levels in the eight patients increased to 384% of the upper limit, whereas free T4 and T3 values decreased but remained within the reference range. Levothyroxine dosage was incrementally increased up to an average of 206%, but hypothyroidism could only be reversed in three patients in whom the condition was recognized relatively early. TSH levels returned to normal in the other five patients following discontinuation of imatinib. Separating the times of administration of levothyroxine and imatinib did not appear to help. The interaction may also occur with other forms of thyroid replacement therapy, although clinical data are lacking.
MANAGEMENT: Monitoring of thyroid function including laboratory serum TSH concentrations should be performed before, during, and after any dosage change or discontinuation of imatinib therapy, and the levothyroxine dosage adjusted accordingly. The authors of the study cited above suggest a minimum 2-fold increase in levothyroxine therapy before initiation of imatinib treatment and close monitoring of thyroid function during treatment.
See also...
Drug Interaction Classification
The classifications below are a guideline only. The relevance of a particular drug interaction to a specific patient is difficult to determine using this tool alone given the large number of variables that may apply.
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
Do not stop taking any medications without consulting your healthcare provider.
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