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Drug Interactions between diphenhydramine and rolapitant

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

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Interactions between your drugs

Moderate

diphenhydrAMINE rolapitant

Applies to: diphenhydramine and rolapitant

MONITOR: Coadministration with rolapitant may increase the plasma concentrations of drugs that are substrates of the CYP450 2D6 isoenzyme. Rolapitant is a moderate CYP450 2D6 inhibitor, with inhibitory effect lasting at least 7 days after a single dose. When a 30 mg dose of dextromethorphan, a CYP450 2D6 probe substrate, was administered with a 180 mg dose of rolapitant on day 1 of a pharmacokinetic study, dextromethorphan peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 120% and 160%, respectively. When dextromethorphan was administered on day 8 without rolapitant, Cmax and AUC increased by 180% and 230%, respectively. The duration of CYP450 2D6 inhibition was not studied beyond 7 days and may last longer.

MANAGEMENT: Caution is advised when rolapitant is prescribed with drugs that are significantly metabolized by CYP450 2D6, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever rolapitant is added to or withdrawn from therapy. Due to the prolonged duration of CYP450 2D6 inhibition by rolapitant, prolonged monitoring for adverse effects of drugs that are substrates of CYP450 2D6 may be required for at least 28 days after administration of rolapitant.

References (1)
  1. (2015) "Product Information. Varubi (rolapitant)." Tesaro Inc.

Drug and food interactions

Moderate

diphenhydrAMINE food

Applies to: diphenhydramine

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

References (1)
  1. Linnoila M (1973) "Drug effects on psychomotor skills related to driving: interaction of atropine, glycopyrrhonium and alcohol." Eur J Clin Pharmacol, 6, p. 107-12

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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