Digoxin with Trimethoprim Interaction Details
Brand Names Associated with Digoxin
- Cardoxin®
- Digitek®
- Digoxin
- Lanoxicaps®
- Lanoxin®
Brand Names Associated with Trimethoprim
- Primsol®
- Proloprim®
- Trimethoprim
- Trimpex®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Jan 08, 2024
Interaction Effect
An increased risk of digoxin toxicity
Interaction Summary
Coadministration of digoxin and trimethoprim resulted in a 22% to 28% increase in digoxin serum concentrations; increases of 30% to 50% have been reported in elderly patients . Measure digoxin concentrations prior to initiation of concurrent use. Reduce the digoxin dose (by approximately 15% to 30% for oral) or modify the dosing frequency. Continue monitoring digoxin plasma concentration levels .
Severity
Major
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Coadministration of digoxin and trimethoprim may increase digoxin plasma concentrations. Measure digoxin concentrations prior to initiation of concurrent use. Reduce the digoxin dose (by approximately 15% to 30% for oral) or modify the dosing frequency. Continue monitoring digoxin plasma concentration levels.
Mechanism Of Interaction
Decreased renal tubular secretion of digoxin
Literature Reports
A) In pharmacokinetic studies, coadministration of digoxin and trimethoprim resulted in a 22% to 28% increase in digoxin serum concentrations .
B) A study of 9 elderly patients stabilized on digoxin therapy showed that the addition of trimethoprim 200 mg twice daily for 2 weeks significantly altered the serum concentrations of digoxin. All patients had normal serum creatinine values and no signs of hepatic or cardiac disease. Immediately prior to the addition of trimethoprim, digoxin serum concentrations averaged 1.0 nmol/L. Serum digoxin concentrations increased to 1.3 nmol/L after 7 days of trimethoprim administration and 1.5 nmol/L after 14 days. Seven days after the discontinuation of trimethoprim, digoxin levels had decreased to 0.9 nmol/L .
C) Six healthy young male subjects received a single IV infusion of digoxin 1 mg over 15 minutes, followed by 4 days of intermittent venous blood samples. On the fifth day, participants were started on oral trimethoprim 200 mg twice daily. Another IV dose of digoxin was given on day 10. Digoxin renal clearance was reduced by 17%, from an average of 1.93 mL/min/kg to 1.61 mL/min/kg. Digoxin total body clearance, extra renal clearance, and glomerular filtration rate were not significantly affected by the administration of trimethoprim .
Digoxin Overview
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Digoxin is used to treat heart failure and abnormal heart rhythms (arrhythmias). It helps the heart work better and it helps control your heart rate.
Trimethoprim Overview
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Trimethoprim eliminates bacteria that cause urinary tract infections. It is used in combination with other drugs to treat certain types of pneumonia. It also is used to treat traveler's diarrhea. Antibiotics will not work for colds, flu, or other viral infections.
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This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
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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.