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Nelfinavir Tablets and Phenytoin Sodium

Determining the interaction of Nelfinavir Tablets and Phenytoin Sodium and the possibility of their joint administration.

Check result:

Nelfinavir Tablets <> Phenytoin Sodium

Relevance: 23.12.2022 Reviewer: Shkutko P.M., M.D., in

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Consumer:

Nelfinavir may reduce the blood levels and effects of phenytoin. Contact your doctor if your symptoms worsen or your condition changes during treatment with these medications. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Professional:

MONITOR: Coadministration with nelfinavir may decrease the plasma concentrations of phenytoin. The proposed mechanism is nelfinavir induction of phenytoin metabolism via CYP450 2C9. In 12 study subjects, administration of phenytoin (300 mg once daily for 14 days) in combination with nelfinavir (1250 mg twice daily for 7 days) decreased mean phenytoin peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) by 21%, 29% and 39%, respectively, compared to administration of phenytoin alone. The pharmacokinetics of nelfinavir were not significantly altered. The interaction was suspected in a case report of a 30-year-old HIV-infected patient receiving phenobarbital 100 mg and phenytoin 300 mg per day for generalized tonic-clonic seizures who experienced a seizure recurrence in association with approximately 50% reduced phenytoin levels following initiation of nelfinavir treatment. He had been stabilized on his anticonvulsant regimen for three years, and his last known seizure was 4 years prior to this episode. The seizure was controlled with diazepam 10 mg and phenytoin 100 mg.

MANAGEMENT: The potential for reduced therapeutic effects of phenytoin should be considered during coadministration with nelfinavir. Phenytoin serum levels and pharmacologic effects should be closely monitored and the dosage adjusted accordingly, particularly following initiation or discontinuation of nelfinavir in patients who are stabilized on their anticonvulsant regimen. No dosage adjustment for nelfinavir is recommended.

References

"Product Information. Dilantin (phenytoin)." Parke-Davis, Morris Plains, NJ.
Honda M, Yasuoka A, Aoki M, Oka S "A generalized seizure following initiation of nelfinavir in a patient with human immunodefieciency virus type 1 infection, suspected due to interaction between nelfinavir and phenytoin." Intern Med 38 (1999): 302-3
Durant J, Clevenbergh P, Garraffo R, Halfon P, Icard S, DelGiudice P, Montagne N, Schapiro JM, Dellamonica P "Importance of protease inhibitor plasma levels in HIV-infected patients treated with genotypic-guided therapy: pharmacological data from the Viradapt Study." Aids 14 (2000): 1333-9
"Product Information. Viracept (nelfinavir)." Agouron Pharma Inc, La Jolla, CA.
Liedtke MD, Lockhart SM, Rathbun RC "Anticonvulsant and antiretroviral interactions." Ann Pharmacother 38 (2004): 482-9

Nelfinavir Tablets

Generic Name: nelfinavir

Brand name: Viracept

Synonyms: Nelfinavir

What is Nelfinavir Tablets?

Phenytoin Sodium

Generic Name: phenytoin

Brand name: Dilantin, Dilantin Infatabs, Phenytek, Phenytoin Sodium, Prompt

Synonyms: n.a.

What is Phenytoin Sodium?

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In the course of checking the drug compatibility and interactions, data from the following reference sources was used: Drugs.com, Rxlist.com, Webmd.com, Medscape.com.

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