Dilantin® Jeopardy: Avoiding The Dangers of Phenytoin

MedSurg Nursing, Dec, 1998 by Michael L. Schlicher

ASA

Chlorpromazine

Diazepam

Drugs that Decrease Serum Dilantin Levels

Chronic ETOH

Folic acid

Antacids

Drugs that Dilantin Causes an Inhibitory Effect

Insulin

Vitamin D

Oral contraceptives

Lasix

Quinidine

Drugs that Dilantin can Potentiate Effectiveness

Oral anticoagulants

Antihypertensives

Inderal

Valproic acid

Thyroid-stimulating hormone

Nursing Considerations/ Patient Education

It is imperative that nurses educate patients regarding phenytoin's features and various interactions. As with any anticonvulsant, patients should be cautioned to avoid driving until their response to the medication is known and assessed as safe. The importance of maintaining good oral hygiene during therapy and seeing a dentist frequently for teeth cleaning should be stressed. Dental health is a particular concern for patients younger than 23 years of age and those taking doses more than 500 mg/day because they are at increased risk for gingival hyperplasia (United States Pharmacopeial, 1996).

Patients' urine may turn pink, red, or reddish brown due to phenytoin, which is not abnormal. Diabetic patients should be instructed to keep a careful watch on their blood sugar levels and notify their doctor if they notice significant changes in their blood sugar. Patients should be reminded that all doses of phenytoin should be taken on time and that they should not stop their medication without advice from their doctor or nurse practitioner. Patients who miss a dose should be advised not to double up on their next dose. Instead they should take their missed dose as soon as possible, unless it is almost time for the next dose. In that case, they should not take the missed dose at all; just return to their regular dosing schedule. For those taking PO phenytoin it is best to take the drug with food to help avoid GI upset. Nurses should instruct parents with neonates or children on phenytoin suspension to make sure they shake the suspension thoroughly and give the medication immediately after shaking. And finally, brands or dosage forms should not be changed without first checking for comparability as absorption can vary between brands.

Alternatives to Phenytoin

Recently, the FDA approved the release of fosphenytoin (Cerebyx[R]) as a possible alternative to regular phenytoin. Fosphenytoin is a prodrug of phenytoin, meaning it is rapidly converted in the body to the active drug, phenytoin. Fosphenytoin is indicated for short-term parenteral administration when formulations of phenytoin are unavailable, inappropriate, or deemed less advantageous (Parke-Davis, 1996). Advantages of fosphenytoin include superior infusion site tolerability and faster administration. Unlike phenytoin, fosphenytoin can safely be given IM and can achieve therapeutic levels within 30 minutes of IM loading doses. It can also be used with D5W or normal saline (Tomich, 1996). Disadvantages of fosphenytoin are its high cost and the lack of information regarding drug compatibility. Also, because it is rapidly and completely converted to phenytoin, dosing will be written in phenytoin equivalents (PE) per minute which may be somewhat confusing and unfamiliar for most nurses. The systemic side effects, however, will remain similar since it becomes phenytoin. Up to half the patients taking fosphenytoin complain of itching, particularly in the groin and perineal areas. Nevertheless, fosphenytoin will soon be widely available as a viable alternative to regular phenytoin.