What are the Phenytoin Side Effects?

Phenytoin is a common antiepileptic drug that, despite being considered effective, carries many potential risks. Side effects of phenytoin can range from minor gastrointestinal upsets and rashes to more severe allergic reactions and yellowing of the skin or eyes. Those who are pregnant, as well as the elderly and those with decreased liver functions, are discouraged from taking this medication as it may potentially pose a risk.

Some of the milder phenytoin side effects may include stomach upsets such as nausea, vomiting, and constipation. Other common interactions can include dizziness and headache, a mild feeling of nervousness, and trouble falling asleep. These phenytoin side effects are quite common, and may go away within a few days of beginning the drug. In some cases they may not, and patients are often advised to seek professional medical attention if they persist or become bothersome.

More severe phenytoin side effects can include allergic reactions. An allergic reaction may appear as difficulty breathing or a tightness of chest, as well as a swelling of the tongue, mouth, lips, or face. The appearance of a rash is not uncommon and usually subsides over time, but it may also be an indication of an allergic reaction to this drug. Measles-like rashes are the most common sign of a skin allergy, but large blisters or infected lesions may also occur.

Phenytoin side effects may also appear in the liver or nervous system. Elevated enzymes and liver function tests may occur while taking phenytoin, as may acute or chronic persistent hepatitis, cholestasis, or fulminant hepatic failure. The nervous system may also show changes such as impaired thought processes, slurred speech, or lethargy. More severe side effects may present themselves, and can include psychiatric illness, involuntary movement, or coma.

Other side effects may include hypersensitivity and immunologic conditions. Phenytoin may cause a deficiency in folic acid and enlargement of the gums, and certain types of anemia may occur. Acute pulmonary disease and cardiovascular conditions may also pose a potential risk.

Phenytoin may bear serious side effects for women and children before and after pregnancy. For the mother, this medication might present an increased risk of seizure, as the dosage may be significantly altered. For the child, it may cause malformations such as heart conditions or facial clefts, as well as mental deficiencies or growth abnormalities. After delivery, the baby may also suffer from a bleeding disorder due to insufficient vitamin K.