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Drug Interactions between amprenavir and cimetidine

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

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Interactions between your drugs

Minor

cimetidine amprenavir

Applies to: cimetidine and amprenavir

The coadministration with drugs that are inhibitors of the CYP450 3A4 enzymatic pathway may increase the plasma concentrations of amprenavir, which is metabolized by CYP450 3A4. The possibility of prolonged and/or increased pharmacologic effects of amprenavir should be considered. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate whenever a CYP450 3A4 inhibitor is added to or withdrawn from therapy. Patients should be advised to notify their physician if they experience nausea, vomiting, diarrhea, or a rash.

References

  1. "Product Information. Agenerase (amprenavir)." Glaxo Wellcome PROD (2001):

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Drug and food interactions

Moderate

amprenavir food

Applies to: amprenavir

GENERALLY AVOID: Administration with a high-fat meal may decrease the oral bioavailability of amprenavir. The mechanism is unknown. In healthy volunteers, consumption of a standardized high-fat meal decreased the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of amprenavir (1200 mg single oral dose) by 36% and 21%, respectively, compared to administration in the fasted state. The time to reach Cmax (Tmax) was increased 44% following a high-fat meal.

Grapefruit juice does not appear to significantly affect the pharmacokinetics of amprenavir. In 12 healthy volunteers, administration with grapefruit juice (200 mL) decreased the mean peak plasma concentration (Cmax) of amprenavir (1200 mg single oral dose) by 22% compared to water. The median time to reach Cmax (Tmax) was prolonged from 0.75 to 1.13 hours. These pharmacokinetic changes are not thought to be clinically significant, since antiretroviral response is more closely associated with systemic exposure (AUC) and trough plasma concentration (Cmin), which were not affected in the study.

MANAGEMENT: Amprenavir may be taken with or without food, but should not be taken with a high-fat meal.

References

  1. "Product Information. Agenerase (amprenavir)." Glaxo Wellcome PROD (2001):
  2. Demarles D, Gillotin C, Bonaventure-Paci S, Vincent I, Fosse S, Taburet AM "Single-dose pharmacokinetics of amprenavir coadministered with grapefruit juice." Antimicrob Agents Chemother 46 (2002): 1589-1590

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Minor

cimetidine food

Applies to: cimetidine

Concurrent use of cimetidine and ethanol may result in increased ethanol concentrations. The mechanism appears to be due to inhibition of gastric alcohol dehydrogenase by cimetidine, leading to increased bioavailability of the alcohol and inhibition of hepatic metabolism of alcohol. The clinical significance of this interaction is limited. More importantly, patients requiring cimetidine for gastrointestinal disease should be counseled to avoid alcohol to prevent worsening of their disease. The other H-2 receptor antagonists appear to have minimal effects on the concentrations of alcohol.

References

  1. Feely J, Wood AJ "Effects of cimetidine on the elimination and actions of ethanol." JAMA 247 (1982): 2819-21
  2. Hansten PD "Effects of H2-receptor antagonists on blood alcohol levels." JAMA 267 (1992): 2469

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Minor

cimetidine food

Applies to: cimetidine

Caffeine effects may be increased in patients also taking cimetidine. The mechanism may be due to decreased caffeine metabolism induced by cimetidine. Although adequate clinical data are lacking, a reduction in dose or elimination of caffeine may be needed if excess CNS stimulation is observed.

References

  1. "Product Information. Tagamet (cimetidine)." SmithKline Beecham PROD (2001):
  2. Broughton LJ, Rodgers HJ "Decreased systenuc clearance of caffeine due to cimetidine." Br J Clin Pharmacol 12 (1981): 155-9

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Minor

cimetidine food

Applies to: cimetidine

H2 antagonists may reduce the clearance of nicotine. Cimetidine, 600 mg given twice a day for two days, reduced clearance of an intravenous nicotine dose by 30%. Ranitidine, 300 mg given twice a day for two days, reduced clearance by 10%. The clinical significance of this interaction is not known. Patients should be monitored for increased nicotine effects when using the patches or gum for smoking cessation and dosage adjustments should be made as appropriate.

References

  1. Bendayan R, Sullivan JT, Shaw C, Frecker RC, Sellers EM "Effect of cimetidine and ranitidine on the hepatic and renal elimination of nicotine in humans." Eur J Clin Pharmacol 38 (1990): 165-9

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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.

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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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