Atazanavir / ritonavir

Phenytoin

Not recommended association.

No pharmaceutical opinion available for this interaction.

Mechanism

Atazanavir / ritonavir may possibly induce the metabolism (CYP 2C9) and consequently decrease the concentration of Phenytoin.

Phenytoin may possibly induce the metabolism and decrease the plasma concentration of Atazanavir / ritonavir.

Atazanavir / ritonavir

Pharmacodynamic effects

Possible decrease of clinical efficacy.

Recommendations

Monitor for signs and symptoms of therapeutic failure.

An increase in dosage may be necessary.

Should not be administered without low-dose ritonavir.

Alternative solution(s)

Phenytoin

Pharmacodynamic effects

Possible decrease of clinical efficacy.

Recommendations

Avoid if possible. Use an alternative or monitor patient closely.

Monitor for signs and symptoms of therapeutic failure.

An increase in dosage may be necessary.

Alternative solution(s)

Gabapentin, pregabalin, leviracetam.

Monitor

Tests

Phenytoin

Atazanavir plasma level

CD4+

Viral load HIV

Pharmacokinetic parameters

Comment

Reference
  • 1382
    Atazanavir (Reyataz), Bristol-Myers Squibb, Quebec, Canada, 26 octobre 2018.
  • 3142
    Phenytoine (Dilantin), Pfizer, Québec, Canada, 22 juil 2013.
  • 122
    Ritonavir (Norvir), Corporation AbbVie, Quebec, Canada, 5 juillet 2021.