Ranitidine with Warfarin Interaction Details
Brand Names Associated with Ranitidine
- Ranitidine
- Tritec®
- Zantac®
- Zantac® 75
- Zantac® EFFERdose®
- Zantac® Syrup
Brand Names Associated with Warfarin
- Coumadin®
- Jantoven®
- Warfarin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 25, 2023
Interaction Effect
An increased risk of bleeding
Interaction Summary
Concomitant ranitidine and warfarin has resulted in altered prothrombin times. In adults, ranitidine at doses exceeding 150 mg twice daily inhibits hepatic metabolism of warfarin over one to two weeks and may increase levels by up to 27%. Once ranitidine is discontinued, it takes approximately three to seven days to return to a pretreatment state. The administration of ranitidine and warfarin does not appear to be clinically significant in the majority of patients . Due to the narrow therapeutic index, close monitoring of prothrombin time is recommended during coadministration with ranitidine. .
Severity
Moderate
Onset
Delayed
Evidence
Probable
How To Manage Interaction
Altered prothrombin time has been reported among patients receiving concomitant ranitidine and warfarin. Due to the narrow therapeutic index, use of ranitidine in patients requiring anticoagulant therapy with warfarin should be accompanied by frequent monitoring of the prothrombin time until any effect on the anticoagulant response is manifested and is stabilized. In patients whose prothrombin times are unstable while receiving warfarin and ranitidine, consider using an H2-antagonist less likely to interact with warfarin, such as famotidine or nizatidine.
Mechanism Of Interaction
Decreased warfarin metabolism
Literature Reports
A) Data indicate that the clearance of warfarin is reduced similarly by ranitidine and cimetidine. Ranitidine 150 mg twice daily resulted in a 27% decrease in the apparent oral clearance of warfarin; cimetidine 1 g orally daily resulted in a 36% decrease. With ranitidine in doses of 750 mg daily, a greater decrease in warfarin clearance was observed than with lower doses. With oral cimetidine 200 mg twice daily, a smaller decrease in clearance was observed than with the 1 g daily doses. The clinical significance of this reduction in clearance is unknown since prothrombin times were not measured .
B) A 65-year-old patient experienced hematemesis and prolongation of the prothrombin time to 36.7 seconds (control 10.8 to 12.4 seconds) following the concomitant administration of ranitidine 600 mg daily and warfarin 5 mg daily for 11 days. Ranitidine was reduced to the patient's previous maintenance dose of 300 mg daily, and all other medications and diet remained the same. The prothrombin time fell to 19 to 20 seconds. A dose relationship may exist or specific patient populations may be predispose to an interaction between ranitidine and warfarin; further studies are required .
C) Cimetidine appears to influence the pharmacokinetics of warfarin to a greater extent than ranitidine; however, the clinical significance of these alterations has not been determined .
Ranitidine Overview
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Ranitidine is used to treat ulcers; gastroesophageal reflux disease (GERD), a condition in which backward flow of acid from the stomach causes heartburn and injury of the food pipe (esophagus); and conditions where the stomach produces too much acid, such as Zollinger-Ellison syndrome. Over-the-counter ranitidine is used to prevent and treat symptoms of heartburn associated with acid indigestion and sour stomach. Ranitidine is in a class of medications called H2 blockers. It decreases the amount of acid made in the stomach.
Warfarin Overview
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Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants ('blood thinners'). It works by decreasing the clotting ability of the blood.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.