Methimazole and Quetiapine interaction
Methimazole and Quetiapine: the Quetiapine prescribing label describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Quetiapine (SEROQUEL XR) label · effective 2026-04-10
Hypothyroidism Adults: Clinical trials with quetiapine demonstrated dose-related decreases in thyroid hormone levels.
In SEROQUEL XR clinical trials across all indications 1.8% (24/1336) of patients on SEROQUEL XR versus 0.6% (3/530) on placebo experienced decreased free thyroxine (<0.8 LLN) and 1.6% (21/1346) on SEROQUEL XR vs. 3.4% (18/534) on placebo experienced increased thyroid stimulating hormone (TSH).
Some patients with TSH increases needed replacement thyroid treatment.
The mechanism by which quetiapine effects the thyroid axis is unclear.
If there is an effect on the hypothalamic-pituitary axis, measurement of TSH alone may not accurately reflect a patient’s thyroid status.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.