Is Fosphenytoin Safe in Breastfeeding

I am a breastfeeding mother and i want to know if it is safe to use Fosphenytoin? Is Fosphenytoin safe for nursing mother and child? Does Fosphenytoin extracts into breast milk? Does Fosphenytoin has any long term or short term side effects on infants? Can Fosphenytoin influence milk supply or can Fosphenytoin decrease milk supply in lactating mothers?

No information is available on the clinical use of fosphenytoin during breastfeeding. However, fosphenytoin is rapidly metabolized in the body to the active drug phenytoin. Breastfeeding during phenytoin monotherapy does not appear to adversely affect infant growth or development, and breastfed infants had higher IQs and enhanced verbal abilities than nonbreastfed infants at 6 years of age in one study.[1] If phenytoin is required by the mother, it is not necessarily a reason to discontinue breastfeeding. Because of the low levels of phenytoin in breastmilk, amounts ingested by the infant are small and usually cause no difficulties in breastfed infants when used alone except for rare idiosyncratic reactions. Combination therapy with sedating anticonvulsants or psychotropics may result in infant sedation or withdrawal reactions. In one case report, maternal phenytoin dosage requirements decreased as breastfeeding was discontinued.[2]

A mother was taking phenobarbital 390 mg daily and phenytoin 400 mg daily during pregnancy and postpartum. Her infant was drowsy at birth, refused to suck and was given partial formula feeding. At 5 days of age, her infant was admitted to the hospital pale and collapsed with bruising, bleeding, and a decreased hemoglobin, thought to be due to methemoglobinemia. Breastfeeding was discontinued and the infant was given a transfusion which rapidly improved her condition. On day 10, the mother resumed breastfeeding the infant. Within 24 hours the infant was extremely sedated and refused to suck and was fed breastmilk with a spoon. The sedation persisted for 2 days until breastmilk was discontinued permanently because of a return of methemoglobinemia. The extreme sedation was probably due to phenobarbital in the milk and the methemoglobinemia was probably caused by the phenytoin.[14] One clinician reported that the breastfed infants of 28 mothers who were taking phenytoin 100 to 200 mg 3 times daily had no adverse reactions including drowsiness or lethargy.[15] No adverse effects were noted in the breastfed neonates of 2 mothers who were taking phenytoin 300 mg daily.[3] A 10-week-old breastfed infant whose mother was taking clemastine, phenytoin and carbamazepine was drowsy, refused to feed, was irritable, and had high-pitched crying.[16] These side effects were possibly caused by clemastine in breastmilk, but the other drugs could also have contributed. A probable case of drug-induced drowsiness occurred in a newborn whose mother was taking primidone, carbamazepine and phenytoin (dosages not stated). At day 30, breastfeeding was discontinued because of the drowsiness that occurred after each feeding and poor weight gain. The same group of researchers found that 15 partially breastfed infants whose mothers were taking various anticonvulsants, including phenytoin, gained weight at a slower rate during the first 5 days postpartum than did 75 infants of epileptic mothers who bottle fed or control mothers taking no medications.[17] Drowsiness, pallor and feeding difficulties in a 2-week-old were possibly caused by primidone and phenytoin in breastmilk. Possible drug-related drowsiness, pallor and feeding difficulties were reported in a 4-day-old whose mother was taking primidone, phenobarbital, phenytoin and sulthiame.[18] Although phenytoin might have contributed to these outcomes, it is more likely that they were due primarily to the more sedating anticonvulsants, primidone and phenobarbital. Two breastfed infants (one full, one partial) whose mothers took phenytoin during pregnancy and postpartum became hyperexcitable when their serum phenytoin dropped to unmeasurable levels at 3 to 6 weeks of age.[19] In a long-term study on infants exposed to anticonvulsants during breastfeeding, no difference in average intelligence quotient at 3 years of age was found between infants who were breastfed (n = 17) a median of 6 months and those not breastfed (n = 23) when their mothers were taking phenytoin.[20] At 6 years of age, extensive psychological and intelligence testing found no difference between the breastfed and nonbreastfed infants.[1]