phenytoin, Dilantin, Dilantin-125 (cont.)

Pharmacy Author:

Omudhome Ogbru, PharmD

Omudhome Ogbru, PharmD

Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

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Medical and Pharmacy Editor:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

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Drugs that may decrease phenytoin levels and reduce effectiveness include carbamazepine, chronic alcohol abuse, reserpine, and sucralfate (Carafate).

The oral absorption of phenytoin can be reduced by any of the following:

• antacids containing magnesium,
• calcium carbonate, or aluminum;
• calcium salts; or enteral feeding products (tube feedings).

Separating the administration of phenytoin and enteral feeding products, antacids, or calcium salts by at least 2 hours will help avoid this interaction.

PREGNANCY: There is an increased risk of malformations and birth defects in women taking phenytoin. Thus, phenytoin should be used in pregnancy only if the physician feels that the potential benefit outweighs the risk.

NURSING MOTHERS: Phenytoin is secreted into breast milk. Breast feeding is not recommended for persons taking phenytoin.

SIDE EFFECTS: Many adverse effects can occur during phenytoin therapy including dizziness, drowsiness, difficulty focusing (vision), unsteady gate, tiredness, abnormal involuntary movements, nausea, vomiting, constipation, abdominal pain, and loss of appetite.

Children and young adults can develop overgrowth of the gums during long-term therapy which requires regular treatment by a dentist. Good oral hygiene and gum massage may reduce the risk. R

ashes can occur in between 1 in 20 and 1 in 10 persons; some may be severe. Additionally, darkening coloration of the skin may develop (more commonly in women). Phenytoin can produce unusual growth of hair in some patients. This reaction most commonly affects the arms and legs but can also affect the trunk and face; it may be irreversible.

Various lymph node reactions have been reported with phenytoin therapy. Lymph nodes may swell, sometimes painfully.

Phenytoin causes serum glucose (sugar) to rise. Thus, blood sugar should be monitored closely when phenytoin is administered to patients with diabetes.

Phenytoin can potentially injure the liver although this is an uncommon occurrence.

Phenytoin can cause the platelet or white blood cell counts to drop, increasing the risk of bleeding or infection, respectively. Phenytoin also can cause anemia.

Because it interferes with vitamin D metabolism, phenytoin can cause weakening of the bones (osteomalacia).

Phenytoin can cause sexual dysfunction including decreased libido, impotence, and priapism (painful, prolonged erections).

Antiepileptic medications have been associated with an increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need for the antiepileptic drug. Patients who begin antiepileptic therapy should be closely observed for clinical worsening, suicidal thoughts or unusual changes in behavior.

Reference: FDA Prescribing Information

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