Famotidine with Fosamprenavir Interaction Details
Brand Names Associated with Famotidine
- Duexis® (as a combination product containing Famotidine, Ibuprofen)
- Famotidine
- Fluxid®
- Pepcid®
- Pepcid® AC
- Pepcid® Complete (as a combination product containing Calcium Carbonate, Famotidine, Magnesium Hydroxide)
- Pepcid® RPD
Brand Names Associated with Fosamprenavir
- Fosamprenavir
- Lexiva®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 13, 2023
Interaction Effect
Decreased fosamprenavir absorption and reduction of amprenavir efficacy (active fosamprenavir metabolite)
Interaction Summary
Concomitant use of fosamprenavir and famotidine is not recommended due to the risk of reduced fosamprenavir absorption, which is dependent on gastric pH and may reduce the efficacy of amprenavir, the active metabolite of fosamprenavir . In a study, when the gastric pH was raised with ranitidine, the concomitant use of fosamprenavir resulted in a decrease in amprenavir AUC of 30% and Cmax of 51% .
Severity
Major
Onset
Unspecified
Evidence
Theoretical
How To Manage Interaction
Concomitant use of fosamprenavir and famotidine is not recommended due to the risk of reduced fosamprenavir absorption, which is dependent on gastric pH, and the potential for reduced amprenavir efficacy (active metabolite of fosamprenavir) .
Mechanism Of Interaction
Increase in gastric pH
Literature Reports
A) Pharmacokinetic parameters (AUC and Cmax) of amprenavir decreased significantly in healthy adult patients treated with concomitant fosamprenavir and ranitidine, a histamine H2-receptor antagonist, compared to those treated with fosamprenavir only in a single-dose, randomized, cross-over study (N=26). Fosamprenavir 1400 mg was administered followed by a 4- to 7-day washout period. Then, fosamprenavir 1400 mg was administered 1 hour after ranitidine 300 mg. Compared to fosamprenavir alone, fosamprenavir plus ranitidine resulted in a decrease in amprenavir AUC of 30% and a decrease in amprenavir Cmax of 51% .
Famotidine Overview
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Prescription famotidine is used to treat ulcers (sores on the lining of the stomach or small intestine); gastroesophageal reflux disease (GERD, a condition in which backward flow of acid from the stomach causes heartburn and injury of the esophagus [tube that connects the mouth and stomach]); and conditions where the stomach produces too much acid, such as Zollinger-Ellison syndrome (tumors in the pancreas or small intestine that cause increased production of stomach acid). Over-the-counter famotidine is used to prevent and treat heartburn due to acid indigestion and sour stomach caused by eating or drinking certain foods or drinks. Famotidine is in a class of medications called H2 blockers. It works by decreasing the amount of acid made in the stomach.
Fosamprenavir Overview
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Fosamprenavir is used along with other medications to treat human immunodeficiency virus (HIV) infection. Fosamprenavir is in a class of medications called protease inhibitors. It works by decreasing the amount of HIV in the blood. Although fosamprenavir does not cure HIV, it may decrease your chance of developing acquired immunodeficiency syndrome (AIDS) and HIV-related illnesses such as serious infections or cancer. Taking these medications along with practicing safer sex and making other life-style changes may decrease the risk of transmitting the HIV virus to other people.
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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.