DILANTIN (phenytoin)
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Tradename Dilantin
Manufacturer Parke-Davis
Treatment Class Psychopharmacologic and Neurologic (CNS)
Indication Refractory partial epilepsy

Patients should not rely solely on the validity of statements made here, but should seek sound medical advice from their physicians.

QUESTION 1: What are the guidelines for folic acid supplementation while on phenytoin during pregnancy?

Regarding folate supplementation for epileptic women on AEDs preparing for and during pregnancy, specifically phenytoin: what is recommended daily folic acid dose? Some litertature mentions .4-.8mg/day TID or BID, others recommend 4-5mg/day. What's correct?

ANSWER: In response to your question, there are no set guidelines for folic acid supplementation while on phenytoin during pregnancy. In review of the available literature, folic acid levels should be monitored on a regular basis and levels should be maintained within the normal range of 1.5 - 7.6 ng/ml. There is data indicating that there is a significant association between low serum and RBC folate levels, especially less than 4 NG/ML (well above the accepted normal range), before and/or early in pregnancy in epileptic women and spontaneous abortions and the occurrence of congenital malformations. It is further recommended that adequate folic acid be consumed daily in patients taking anticonvulsant therapy, either from diet and/or supplementation, to maintain normal serum and RBC levels before and during the first months of pregnancy.

As to a specific dose, there is no recommendation. Several studies have used varying doses with similar outcomes. Doses ranged from 0.1 to 5 mg/day. It is best to monitor serum levels and titrate folic acid supplementation to these values. A dose of 4 - 5 mg/day was not recommended by the CDC in cases where anticonvulsants were given, instead this recommendation was for women who have had prior experiences with neural tube defects without anticonvulsants being part of the equation. Other resources state that folic acid delivery should be slightly higher than what is considered normal (0.4 - 1 mg/day). Folic acid supplementation is a judgement call and only through proper monitoring of levels can the proper dose be elucidated.

University of Maryland Drug Information Service

QUESTION 2: What is the proper phenytoin dose during pregnancy?

Regarding phenytoin dose during pregnancy: I understand need to measure "free, unbound phyenytpon levels". Does it matter if dosing is Dilantin Kapseals, 300mg, hs, or phenytoin 150mg, bid as far as maintaining stable state serum levels and when to measure those levels?

ANSWER: In response to phenytoin dosing, dosing of the Kapseals can be 300 mg qd. Serum levels need to be monitored closely, since pregnancy can increase the metabolism or alter the absorption of phenytoin. At steady state in most patients using the 300 mg daily dose the difference from peak to trough is about 1 to 2 mg/L. Assuming the 150 mg divided doses are of equal bioavailability, the fluctuation is negligible at steady state. Loss of seizure control can occur in pregnant women. Dosage increases may be required if levels drop below unacceptable levels.

The risk of developing congenital abnormalities is increased when on an anticonvulsant during pregnancy. It is important to discuss all available options with epileptic women of child bearing age. If they choose is to continue with the pregnancy, careful monitoring and dose titration is imperative to reduce the risk of adverse events.

University of Maryland Drug Information Service

QUESTION 3: What Additional Side Effects Can be Expected When Alcohol is taken with Dilantin?

My 76 year old grandmother recently had another stroke. The doctors prescribed Dilantin, Teclid and Phenobarbatol to keep her from having another one. She also is an alcoholic. She was told that she could not drink with this medication. Her incompetant doctor informed her last week that she could now start using alcohol again even though she is still on the medications. All of her bottles clearly state that no alcohol should be taken with these drugs. What will happen when she starts drinking with these medications? What additional side effects could occur if she combines alcohol with these drugs?

ANSWER: The most likely effect from the addition of alcohol to this regimen is a shorten period of time to become tired. Respiratory distress from the combination is also a possibility. Maybe the physician was weighing the age of your grandmother against the other factors. That is an issue you will have to discuss with the physician. It is necessary that the physician know the true amount of intake to make a valid assessment.

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