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Drug Interactions between fenfluramine and Phenytek

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

phenytoin fenfluramine

Applies to: Phenytek (phenytoin) and fenfluramine

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Coadministration of fenfluramine with potent inducers of CYP450 1A2, 2B6, or 3A4/5 may decrease exposure to fenfluramine and its major active metabolite, norfenfluramine. Over 75% of fenfluramine is metabolized to norfenfluramine prior to elimination, primarily by CYP450 1A2, 2B6 and 2D6, but also to a minor extent by CYP450 2C9, 2C19 and 3A4/5. When a single 0.35 mg/kg dose of fenfluramine oral solution was coadministered with 600 mg once daily rifampin (a weak CYP450 1A2, moderate CYP450 2B6, and potent CYP450 3A4/5 inducer) at steady state in healthy volunteers, fenfluramine peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 40% and 58%, respectively, compared to fenfluramine administered alone. The AUC of norfenfluramine also decreased by 50%, while the Cmax increased by 13%. Reduced efficacy of fenfluramine may occur.

MANAGEMENT: Concomitant use of fenfluramine with potent inducers of CYP450 1A2, 2B6, or 3A4/5 should be avoided when possible. If coadministration is required, monitor the patient for reduced efficacy and consider increasing the dosage of fenfluramine as needed in accordance with the product labeling, but not to exceed the recommended maximum daily dosage. If a potent inducer of CYP450 1A2, 2B6, or 3A4/5 is discontinued during maintenance treatment with fenfluramine, consider a gradual reduction to the fenfluramine dosage that was administered prior to initiating the inducer.

References

  1. "Product Information. Fintepla (fenfluramine)." Zogenix, Inc (2020):

Drug and food interactions

Moderate

phenytoin food

Applies to: Phenytek (phenytoin)

Phenytoin levels may decrease when the suspension is given with enteral feedings. This could lead to a loss of seizure control. You could interrupt the feeding for 2 hours before and after the phenytoin dose. Alternatively, you may give the phenytoin suspension diluted in water and flush the tube with water after administration. These would make it easier for your body to absorb the medication. However, this still may not entirely avoid the interaction and may not always be feasible. You should have your phenytoin levels checked upon starting and stopping of enteral feedings. In addition, using phenytoin together with food may alter the effects of phenytoin. Contact your doctor if you experience worsening of seizure control or symptoms of toxicity, including twitching eye movements, slurred speech, loss of balance, tremor, muscle stiffness or weakness, nausea, vomiting, feeling light-headed, fainting, and slow or shallow breathing. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Ask your doctor before making any changes to your therapy.

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Moderate

fenfluramine food

Applies to: fenfluramine

Using fenfluramine with alcohol can increase the risk of cardiovascular side effects such as increased heart rate, chest pain, or blood pressure changes. In addition, you may also be more likely to experience nervous system side effects such as dizziness, drowsiness, depression, and difficulty concentrating. You should avoid or limit the use of alcohol while being treated with fenfluramine. Do not use more than the recommended dose of fenfluramine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medication without first talking to your doctor.

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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