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Fosphenytoin Pregnancy and Breastfeeding Warnings

Fosphenytoin is also known as: Cerebyx, Sesquient

Medically reviewed by Last updated on Nov 25, 2019.

Fosphenytoin Pregnancy Warnings

This drug should not be used during pregnancy unless the benefit outweighs the risk to the fetus.

US FDA pregnancy category: D

-If this drug is used during pregnancy, or if the patient becomes pregnant while taking the drug, the patient should be informed of the potential harm to the fetus.
-An increase in seizure frequency may occur during pregnancy because of altered phenytoin pharmacokinetics.
-Periodic measurement of plasma phenytoin concentrations may be valuable in the management of pregnant women as a guide to appropriate adjustment of dosage.
-Postpartum restoration of the original dosage will probably be indicated.
-Neonatal coagulation defects (reversible with vitamin K administration) have been reported postpartum.

Administration of this drug to pregnant animals resulted in teratogenicity (increased incidences of fetal malformations) and other developmental toxicity (including embryofetal death, growth impairment, and behavioral abnormalities) in multiple animal species at clinically relevant doses. There are no controlled data in human pregnancy.

-An increased risk of congenital abnormalities ("fetal hydantoin syndrome") has been associated with the use of phenytoin (the active metabolite of this drug) in epileptic women during pregnancy.
-The overall incidence of neonate malformations for offspring of mothers treated with anti-seizure medications is approximately 10%, or 2 to 3 fold the incidence in the general population (although a definite causal relationship has not been established).
-Prenatal exposure to this drug may increase the risks for congenital malformations and other adverse developmental outcomes. Increased frequencies of major malformations (such as orofacial clefts and cardiac defects), minor anomalies (dysmorphic facial features, nail and digit hypoplasia), growth abnormalities (including microcephaly), and mental deficiency have been reported among children born to epileptic women who took this drug alone or in combination with other antiepileptic drugs during pregnancy.
-There have been several reported cases of malignancies, including neuroblastoma, in children whose mothers received phenytoin during pregnancy.

US FDA pregnancy category D: There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

See references

Fosphenytoin Breastfeeding Warnings

-This drug is rapidly metabolized in the body to the active drug phenytoin. Because of the low levels of phenytoin in breastmilk, amounts ingested by the infant are small and usually cause no difficulties when used alone except for rare idiosyncratic reactions. Breastfeeding during phenytoin monotherapy does not appear to adversely affect infant growth or development.
-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.

Use is not recommended.

Excreted into human milk: Unknown; however this drug is metabolized to phenytoin which is excreted in human milk in small amounts

See references

References for pregnancy information

  1. Knott C, Williams CP, Reynolds F "Phenytoin kinetics during pregnancy and the puerperium." Br J Obstet Gynaecol 93 (1986): 1030-7
  2. Paulson GW, Paulson RB "Teratogenic effects of anticonvulsants." Arch Neurol 38 (1981): 140-3
  3. Dam M, Christiansen J, Munck O, Mygind KI "Antiepileptic drugs: metabolism in pregnancy." Clin Pharmacokinet 4 (1979): 53-62
  4. Kochenour NK, Emery MG, Sawchuk RJ "Phenytoin metabolism in pregnancy." Obstet Gynecol 56 (1980): 577-82
  5. Lander CM, Smith MT, Chalk JB, et al "Bioavailability and pharmacokinetics of phenytoin during pregnancy." Eur J Clin Pharmacol 27 (1984): 105-10
  6. "Product Information. Cerebyx (fosphenytoin)." Parke-Davis, Morris Plains, NJ.
  7. Eadie MJ, McKinnon GE, Dickinson RG, et al "Phenytoin metabolism during pregnancy." Eur J Clin Pharmacol 43 (1992): 389-92
  8. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  9. "Teratogenic risks of antiepileptic drugs." Br Med J 283 (1981): 515-6
  10. Monson RR, Rosenberg L, Hartz SC, et al "Diphenylhydantoin and selected congenital malformations." N Engl J Med 289 (1973): 1049-52

References for breastfeeding information

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. United States National Library of Medicine "Toxnet. Toxicology Data Network. Available from: URL:" ([cited 2013 -]):
  3. "Product Information. Cerebyx (fosphenytoin)." Parke-Davis, Morris Plains, NJ.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.