Mirtazapine Use During Breastfeeding
Mirtazapine is safe to use during breastfeeding, with minimal infant exposure and no reported adverse effects in most cases. 1, 2
Key Safety Data
Infant Drug Exposure
- The relative infant dose (RID) of mirtazapine through breast milk is very low, ranging from 0.6% to 2.8% of the maternal weight-adjusted dose, well below the 10% threshold generally considered safe for breastfeeding 1, 2
- The mean RID for mirtazapine is 1.5% and for its metabolite desmethylmirtazapine is 0.4% 1, 2
- Mirtazapine was detected in only 1 of 4 tested infants at a very low level (1.5 mcg/L) 2
Clinical Outcomes
- No adverse effects on breastfed infants have been reported in most published cases 1, 2
- A pooled analysis of 8 breastfeeding mother-infant pairs (maternal doses ranging from 30-120 mg daily) showed no adverse drug effects in any infants 1
- Limited data from 11 exposed neonates suggest safe use during breastfeeding 3
FDA Guidance
The FDA drug label explicitly states that mirtazapine is present in human milk at low levels, with no adverse effects reported in most cases of maternal use 1. The label recommends considering the developmental and health benefits of breastfeeding along with the mother's clinical need for mirtazapine 1.
Clinical Recommendations
When to Use
- Mirtazapine can be continued or initiated during breastfeeding when clinically indicated for maternal depression 1, 2
- The risk-benefit analysis should weigh maternal mental health needs against minimal infant exposure 2
Monitoring
While adverse effects are unlikely, monitor the breastfed infant for:
Important Caveats
- Premature infants or those with neonatal diseases may be more vulnerable to drug exposure, though this risk appears theoretical given the low RID 4
- Each decision should involve individual risk-benefit discussion, though the evidence strongly favors safety 2
- Long-term neurodevelopmental data beyond one year are not available 3
Comparison to Other Antidepressants
Mirtazapine's safety profile during breastfeeding is comparable to SSRIs and TCAs (except doxepin), which are considered compatible with breastfeeding 4. The very low RID of mirtazapine makes it a reasonable option when antidepressant therapy is needed during lactation 2, 3.