Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects or signs of overdose occur:

More common

Bleeding, tender, or enlarged gums (rare with ethotoin); burning, tingling, pain, or itching, especially in the groin—following fosphenytoin injection; clumsiness or unsteadiness; confusion; continuous, uncontrolled back-and-forth and/or rolling eye movements—may be sign of overdose; swollen glands in neck or underarms; fever; muscle pain; skin rash or itching; slurred speech or stuttering—may be sign of overdose; sore throat; trembling—may be sign of overdose; unusual excitement, nervousness, or irritability

Rare

Bone malformations; burning pain at place of injection; chest discomfort; chills and fever; dark urine; dizziness; frequent breaking of bones; headache; joint pain; learning difficulties—in children taking high doses for a long time; light gray-colored stools; loss of appetite; nausea or vomiting; pain of penis on erection; restlessness or agitation; slowed growth; stomach pain (severe); troubled or quick, shallow breathing; uncontrolled jerking or twisting movements of hands, arms, or legs; uncontrolled movements of lips, tongue, or cheeks; unusual bleeding (such as nosebleeds) or bruising; unusual tiredness or weakness; weight loss (unusual); yellow eyes or skin

Rare (with long-term use of phenytoin)

Numbness, tingling, or pain in hands or feet

Symptoms of overdose

Blurred or double vision; clumsiness or unsteadiness (severe); confusion (severe); dizziness or drowsiness (severe); seizures; staggering walk; stuttering or slurred speech

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Constipation; dizziness (mild); drowsiness (mild)

Less common

Diarrhea (with ethotoin); enlargement of jaw; muscle twitching; swelling of breasts—in males; thickening of lips; trouble in sleeping; unusual and excessive hair growth on body and face (more common with phenytoin); widening of nose tip

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.