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Drug Interactions between cimetidine and Iressa

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

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Interactions between your drugs

Major

cimetidine gefitinib

Applies to: cimetidine and Iressa (gefitinib)

ADJUST DOSING INTERVAL: Coadministration with drugs that elevate gastric pH such as H2-receptor antagonists and antacids may decrease the plasma concentrations of gefitinib. According to the manufacturer, the solubility of gefitinib is pH-dependent and decreases sharply between pH 4 and 6, becoming practically insoluble above pH 7. When gefitinib 250 mg was administered to healthy male volunteers (n=26) one hour following two oral 450 mg doses of ranitidine with sodium bicarbonate as needed to achieve a sustained gastric pH above 5.0, mean gefitinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 71% and 47%, respectively, compared to administration of gefitinib alone. High doses of short-acting antacids may have a similar effect if taken regularly in close proximity to gefitinib administration.

MANAGEMENT: The possibility of a diminished therapeutic response to gefitinib should be considered during coadministration with H2-receptor antagonists or antacids. If concomitant treatment is required, the manufacturer recommends administering gefitinib 6 hours before or 6 hours after an H2-receptor antagonist or antacid.

References

  1. (2023) "Product Information. Iressa (gefitinib)." Astra-Zeneca Pharmaceuticals
  2. (2022) "Product Information. Apo-Gefitinib (gefitinib)." Apotex Inc
  3. (2023) "Product Information. Iressa (gefitinib)." AstraZeneca UK Ltd
  4. (2021) "Product Information. Iressa (gefitinib)." AstraZeneca Pty Ltd
  5. Tang W, Tomkinson H, Masson E (2017) "Effect of sustained elevated gastric pH levels on gefitinib exposure." Clin Pharmacol Drug Dev, 6, p. 517-23
View all 5 references

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Drug and food interactions

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 (1982) "Effects of cimetidine on the elimination and actions of ethanol." JAMA, 247, p. 2819-21
  2. Hansten PD (1992) "Effects of H2-receptor antagonists on blood alcohol levels." JAMA, 267, p. 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. (2001) "Product Information. Tagamet (cimetidine)." SmithKline Beecham
  2. Broughton LJ, Rodgers HJ (1981) "Decreased systenuc clearance of caffeine due to cimetidine." Br J Clin Pharmacol, 12, p. 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 (1990) "Effect of cimetidine and ranitidine on the hepatic and renal elimination of nicotine in humans." Eur J Clin Pharmacol, 38, p. 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.

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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