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Drug Interactions between glycerol phenylbutyrate and Norvir

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

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Interactions between your drugs

Moderate

ritonavir glycerol phenylbutyrate

Applies to: Norvir (ritonavir) and glycerol phenylbutyrate

MONITOR: Coadministration of glycerol phenylbutyrate may lead to increased concentrations of CYP450 2D6 substrates. The proposed mechanism is inhibition of CYP450 2D6 by phenylbutyrate, the active moiety of glycerol phenylbutyrate, which has been shown to be an in vitro inhibitor of this isoenzyme. In in vitro studies, administration of phenylbutyrate at a concentration of 800 mcg/mL caused greater than 60% reversible inhibition of CYP450 2D6, 2C9, and 3A4/5. The clinical significance of these results has not been established; however, the manufacturer states that a potential interaction with CYP450 2D6 substrates cannot be ruled out.

MANAGEMENT: Caution is recommended if glycerol phenylbutyrate is administered with medicines that are substrates of CYP450 2D6, such as codeine, dextromethorphan, and some beta blockers (including metoprolol, carvedilol, labetalol, propranolol, and nebivolol). Dosage adjustments as well as clinical and laboratory monitoring may be appropriate.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. (2013) "Product Information. Ravicti (glycerol phenylbutyrate)." Hyperion Therapeutics Inc

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Drug and food interactions

Moderate

ritonavir food

Applies to: Norvir (ritonavir)

ADJUST DOSING INTERVAL: Administration with food may modestly affect the bioavailability of ritonavir from the various available formulations. When the oral solution was given under nonfasting conditions, peak ritonavir concentrations decreased 23% and the extent of absorption decreased 7% relative to fasting conditions. Dilution of the oral solution (within one hour of dosing) with 240 mL of chocolate milk or a nutritional supplement (Advera or Ensure) did not significantly affect the extent and rate of ritonavir absorption. When a single 100 mg dose of the tablet was administered with a high-fat meal (907 kcal; 52% fat, 15% protein, 33% carbohydrates), approximately 20% decreases in mean peak concentration (Cmax) and systemic exposure (AUC) were observed relative to administration after fasting. Similar decreases in Cmax and AUC were reported when the tablet was administered with a moderate-fat meal. In contrast, the extent of absorption of ritonavir from the soft gelatin capsule formulation was 13% higher when administered with a meal (615 KCal; 14.5% fat, 9% protein, and 76% carbohydrate) relative to fasting.

MANAGEMENT: Ritonavir should be taken with meals to enhance gastrointestinal tolerability.

References

  1. (2001) "Product Information. Norvir (ritonavir)." Abbott Pharmaceutical

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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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