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CEREBYX®Medication Guide (fosphenytoin sodium)


Cardiovascular Risk Associated with Rapid Infusion

Inform patients that rapid intravenous administration of CEREBYX increases the risk of adverse cardiovascular reactions, including severe hypotension and cardiac arrhythmias. Cardiac arrhythmias have included bradycardia, heart block, ventricular tachycardia, and ventricular fibrillation which have resulted in asystole, cardiac arrest, and death. Patients should report cardiac signs or symptoms to their healthcare provider [see Warnings and Precautions (5.2)].

Withdrawal of Antiepileptic Drugs

Advise patients not to discontinue use of CEREBYX without consulting with their healthcare provider. CEREBYX should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus [see Warnings and Precautions (5.3)].

Serious Dermatologic Reactions

Advise patients of the early signs and symptoms of severe cutaneous adverse reactions and to report any occurrence immediately to a physician [see Warnings and Precautions (5.4)].

Potential Signs of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) and Other Systemic Reactions

Advise patients of the early toxic signs and symptoms of potential hematologic, dermatologic, hypersensitivity, or hepatic reactions. These symptoms may include, but are not limited to, fever, sore throat, rash, ulcers in the mouth, easy bruising, lymphadenopathy, facial swelling, and petechial or purpuric hemorrhage, and in the case of liver reactions, anorexia, nausea/vomiting, or jaundice. Advise the patient that, because these signs and symptoms may signal a serious reaction, that they must report any occurrence immediately to a physician. In addition, advise the patient that these signs and symptoms should be reported even if mild or when occurring after extended use [see Warnings and Precautions (5.4, 5.5, 5.6, 5.8, 5.9)].


Advise patients to discontinue CEREBYX and seek immediate medical care if they develop signs or symptoms of angioedema such as facial, perioral, or upper airway swelling [see Warnings and Precautions (5.7)].


Advise patients that CEREBYX may cause an increase in blood glucose levels [see Warnings and Precautions (5.16)].

Effects of Alcohol Use and Other Drugs and Over-the-Counter Drug Interactions

Caution patients against the use of other drugs or alcoholic beverages without first seeking their physician's advice [see Drug Interactions (7.1, 7.2)].

Inform patients that certain over-the-counter medications (e.g., cimetidine and omeprazole), vitamins (e.g., folic acid), and herbal supplements (e.g., St. John's wort) can alter their phenytoin levels.

Use in Pregnancy

Inform pregnant women and women of childbearing potential that use of CEREBYX during pregnancy can cause fetal harm, including an increased risk for cleft lip and/or cleft palate (oral clefts), cardiac defects, dysmorphic skull and facial features, nail and digit hypoplasia, growth abnormalities (including microcephaly), and cognitive deficits. When appropriate, counsel pregnant women and women of childbearing potential about alternative therapeutic options. Advise women of childbearing potential who are not planning a pregnancy to use effective contraception while using CEREBYX, keeping in mind that there is a potential for decreased hormonal contraceptive efficacy [see Drug Interactions (7.2)].

Instruct patients to notify their physician if they become pregnant or intend to become pregnant during therapy, and to notify their physician if they are breastfeeding or intend to breastfeed during therapy [see Use in Specific Populations (8.1, 8.2)].

Encourage patients to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry if they become pregnant. This registry is collecting information about the safety of antiepileptic drugs during pregnancy [see Use in Specific Populations (8.1)].

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