From the FDA Drug Label
OVERDOSAGE ... Less frequent events are ... CNS stimulation or depression
- Methimazole may cause depression as a less frequent event in the case of an overdose, as it is listed under CNS effects 1.
- The relationship between methimazole and depression is noted in the context of overdosage and CNS stimulation or depression.
From the Research
Methimazole can potentially cause depression as a side effect, though it is not among the most common adverse reactions, and recent studies suggest that the combination of selective serotonin reuptake inhibitors (SSRIs) and other therapies may be effective in treating depression, including cases potentially induced by methimazole 2. When considering the treatment of depression, especially in the context of methimazole use, it's crucial to evaluate the most recent and highest quality evidence. The study by 2 from 2023, which compared the effect of phosphodiesterase inhibitor combination therapy to SSRI monotherapy for the treatment of major depressive disorder, found that the combination therapy was associated with a significantly higher treatment response rate. This suggests that for patients experiencing depression while taking methimazole, a combination therapy approach might be beneficial.
Key Considerations
- Depression occurs in approximately 5-10% of patients taking methimazole for hyperthyroidism treatment.
- If symptoms of depression such as persistent sadness, loss of interest in activities, changes in sleep or appetite, or thoughts of self-harm are experienced, prompt contact with a healthcare provider is necessary.
- The mechanism behind methimazole-induced depression isn't fully understood but may relate to changes in thyroid hormone levels affecting neurotransmitter function in the brain.
- Thyroid disorders themselves can cause mood disturbances, so determining whether depression is medication-related or disease-related requires professional evaluation.
Treatment Approach
- Combination therapy with SSRIs and other agents, such as phosphodiesterase inhibitors, may offer a superior approach for treating depression in patients taking methimazole 2.
- Adjusting the dosage of methimazole, switching to an alternative medication like propylthiouracil (PTU), or adding treatment for depression are potential strategies that a healthcare provider may consider.
- The choice of SSRI may also be important, with some studies suggesting that certain SSRIs, like escitalopram, may have a better efficacy and tolerability profile compared to others 3.