Trimethoprim/sulfamethoxazole (drug interactions)
Trimethoprim/sulfamethoxazole, commonly known as TMP-SMZ, is a powerful antibiotic combination used to combat bacterial infections by inhibiting the bacteria's ability to utilize folate, which is essential for their growth. While it is effective against a variety of infections, users should be aware of potential drug interactions that could affect treatment outcomes or lead to adverse effects. For instance, taking PABA supplements may reduce the effectiveness of TMP-SMZ, while potassium supplements can lead to dangerously high potassium levels if not supervised by a healthcare provider.
Additionally, combining TMP-SMZ with herbs like white willow or St. John's wort could pose risks, including increased sensitivity to sunlight or adverse reactions. Patients on blood thinners, such as warfarin, should also exercise caution, as the antibiotic may heighten the risk of bleeding. Moreover, concurrent use with medications that elevate potassium levels or methotrexate may amplify toxicity or harmful effects. Given these potential interactions, it is essential for individuals to consult healthcare professionals before starting or combining treatments with TMP-SMZ to ensure safe and effective use.
Trimethoprim/sulfamethoxazole (drug interactions)
RELATED NAME: TMP-SMZ
DEFINITION: An antibiotic combination that provides extra strength in fighting bacteria.
INTERACTIONS: Folate, PABA (para-aminobenzoic acid), potassium, St. John’s wort, white willow, vitamin K, various prescription medications
TRADE NAMES: Bactrim, Cotrim, Septra, Sulfatrim
Folate
Effect: Supplementation Likely Helpful
Both trimethoprim and sulfamethoxazole interfere with folate: The sulfamethoxazole makes it hard for invading bacteria to manufacture folate, and the trimethoprim makes it hard for bacteria to use the folate. The net effect is to starve the bacteria of this necessary vitamin.
Humans and other mammals are much less affected by these antibiotics than bacteria because of how humans process folate. However, trimethoprim can still interfere to some extent with the body’s ability to utilize this essential nutrient. Folate supplementation may be helpful if one takes this antibiotic for a long period of time (to prevent urinary tract infections, for example).
PABA (Para-Aminobenzoic Acid)
Effect: Interference with Action of Drug
The supplement PABA may make trimethoprim/sulfamethoxazole less effective. Persons being treated with this drug should not take PABA except on medical advice.
Potassium
Effect: Possible Harmful Interaction
Trimethoprim/sulfamethoxazole might increase potassium levels in the body. Therefore, persons on long-term treatment with this antibiotic should not take potassium supplements except on the advice of a physician.
White Willow
Effect: Possible Negative Interaction
The herb white willow contains substances very similar to aspirin. On this basis, one should not combine white willow with trimethoprim or sulfamethoxazole.
St. John’s Wort and Other Herbs
Effect: Potential Increased Risk of Photosensitivity
Sulfa drugs can cause increased sensitivity to the sun. Various herbs, including St. John’s wort and dong quai, can also cause this problem. Combined treatment with these herbs and the drug might increase the risk further. Finally, patients are recommended to avoid high doses of vitamin K when taking trimethoprim/sulfamethoxazole as it may increase the risk of blood clots.
Other Interactions
There are several prescription medications individuals should avoid when taking trimethoprim/sulfamethoxazole antibiotics. Blood thinners like warfarin may increase the risk of bleeding. Patients should also avoid taking medications that raise potassium levels, such as angiotensin-converting enzyme (ACE) inhibitors. Taking trimethoprim/sulfamethoxazole with methotrexate may increase toxicity. Several other prescription medications may cause interactions with trimethoprim/sulfamethoxazole. Patients should consult their healthcare provider before combining medications.
Bibliography
Alappan, R., M. A. Perazella, and G. K. Buller. "Hyperkalemia in Hospitalized Patients Treated with Trimethoprim-Sulfamethoxazole." Annals of Internal Medicine, vol. 124, 1996, pp. 316-320.
Kemnic, Tyler R., and Meghan Coleman. "Trimethoprim Sulfamethoxazole." StatPearls, 28 Nov. 2022, www.ncbi.nlm.nih.gov/books/NBK513232. Accessed 21 Sept. 2024.
"Sulfamethoxazole And Trimethoprim (Oral Route) Description and Brand Names." Mayo Clinic, 1 Sept. 2024, www.mayoclinic.org/drugs-supplements/sulfamethoxazole-and-trimethoprim-oral-route/description/drg-20071899. Accessed 21 Sept. 2024.
"Sulfamethoxazole & Trimethoprim Tablets: Uses & Side Effects." Cleveland Clinic, my.clevelandclinic.org/health/drugs/19613-sulfamethoxazole-trimethoprim-tablets. Accessed 21 Sept. 2024.
Vinnicombe, H. G., and J. P. Derrick. "Dihydropteroate Synthase from Streptococcus pneumoniae: Characterization of Substrate Binding Order and Sulfonamide Inhibition." Biochemical and Biophysical Research Communications, vol. 258, 1999, pp. 752-757.