After last week’s post, we received several comments regarding the use of mood stabilizers in breastfeeding women, specifically asking which is safer: lithium or lamotrigine.

Based on the available data, it is difficult to say with certainty which is “safer”.  To date, there has been one report of an adverse event in a nursing infant exposed to lamotrigine.  This was a case of apnea in a 16-day old infant whose mother was taking lamotrigine at a dose of 850 mg/day.  (No other causes of apnea could be determined.)  In a case series of 30 infants exposed to lamotrigine, no adverse events were reported.  No cases of Stevens Johnson syndrome or other serious rash have been reported.

Although there have long been concerns about the use of lithium in nursing mothers, a literature review published in 2000 reported only 2 cases (out of 11) of lithium toxicity.  In a case series of 10 nursing mother-infant pairs, no cases of toxicity or adverse events were reported.

Based on the above numbers, one might argue that the incidence of adverse events is lower with lamotrigine and that this drug is the better choice.  (This assumption is a bit tenuous, given the small numbers involved.)  Nonetheless, we can definitively say that monitoring of the nursing infant is much more intensive when the mother is taking lithium, requiring periodic blood draws.  It is recommended that monitoring include measurement of lithium levels, TSH, BUN and creatinine every 6-8 weeks while the child is nursing.

Given this information, lamotrigine might seem like the better option for nursing women who need a mood stabilizer.  Does this mean we should use lamotrigine in all breastfeeding women who require a mood stabilizer?  Probably not.  Obviously lamotrigine would not be a good option for a woman who has failed to respond to this drug in the past or in a woman who has had an adverse reaction to lamotrigine.  There are at least several other clinical scenarios where lithium might be chosen over lamotrigine.

If a woman has remained stable on lithium throughout her pregnancy, switching to lamotrigine during the postpartum period may increase her risk of relapse.  The postpartum period is a time of high risk in women with bipolar disorder, and, in general, when a woman is stable on a particular regimen during pregnancy, we tend to continue that regimen throughout the postpartum period to minimize the risk of recurrent illness.

If a woman presents with severe depression, especially if accompanied by suicidality, lithium may be preferable.  In this situation, it might take at least 4 to 6 weeks to reach an effective dosage of lamotrigine, whereas the lithium dosage may be pushed to a therapeutic level much more quickly.

If a woman presents with symptoms of hypomania or mania, lithium is probably a better option.  While lamotrigine is FDA-approved for the prevention and treatment of bipolar depression, various studies indicate that lamotrigine alone is not as effective as lithium for managing manic symptoms.

If a woman has responded to lithium in the past but has never tried lamotrigine, it may be more prudent to stick with lithium.  Although we try to chose the safest medication, it is important to select one that we are fairly certain will be effective.  Given that the postpartum period is a time of significant risk, this may not be the ideal time to try a new medication.

The take home message is that mood stabilizers are not freely interchangeable; a woman may respond exquisitely to one mood stabilizer but not to another.  Lamotrigine is an excellent option for some breastfeeding women, but there are some things to keep in mind.  It is important to take into consideration the amount of time required to reach an appropriate dose.  If a woman plans to use lamotrigine during the postpartum period to reduce the risk of postpartum illness (and she has not been taking it during pregnancy), we recommend that she initiates treatment at least 4-6 weeks before the expected time of delivery, so that she has a chance to reach adequate levels of lamotrigine prior to delivery.

Furthermore, it is important to recognize that exclusive breastfeeding frequently leads to sleep deprivation, which can be a trigger for relapse in women with bipolar disorder.  In counseling women with bipolar disorder who plan to breastfeed, we recommend strategies to ensure adequate sleep, including taking naps during the day, intermittent bottle feeding in order to reduce sleep disruption, and relying on others to help with feedings.  While breastfeeding certainly carries many benefits for the baby, maintaining stable mood in the mother is especially important.

Ruta Nonacs, MD PhD

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