{"id":62409,"date":"2024-01-09T10:12:38","date_gmt":"2024-01-09T15:12:38","guid":{"rendered":"https:\/\/www.singlecare.com\/blog\/?p=62409"},"modified":"2024-10-25T10:18:17","modified_gmt":"2024-10-25T14:18:17","slug":"sulfamethoxazole-trimethoprim-interactions","status":"publish","type":"post","link":"https:\/\/www.singlecare.com\/blog\/sulfamethoxazole-trimethoprim-interactions\/","title":{"rendered":"Sulfamethoxazole-trimethoprim interactions to avoid"},"content":{"rendered":"

Sulfamethoxazole-trimethoprim<\/span><\/a> combines two drugs to form a potent antibiotic, recommended for use against <\/span>urinary tract infection<\/span><\/a>, methicillin-resistant staph aureus (MRSA) bacterial infections, pneumocystis <\/span>pneumonia<\/span><\/a>, and bronchitis exacerbations in <\/span>chronic obstructive pulmonary disease (COPD)<\/span><\/a>. Such diverse use of this <\/span>sulfonamide<\/span><\/a> makes it likely you have or will be prescribed it. Recognizing the drug’s pitfalls is important, so you can be safe when taking sulfamethoxazole-trimethoprim, abbreviated SMX-TMP. Among the potential downsides, drug interactions rank near the top in terms of critical information for you to know. <\/span><\/p>\n

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SMX-TMP interacts with certain diabetes meds, antihypertensives, and anticoagulant warfarin, among others. These drug interactions could result in life-threatening heart arrhythmias, hypoglycemia (low blood sugar), or bleeding. Knowing these risks in advance is vital, and a plan should be formed between you and your healthcare team to keep you safe. Here, we will endeavor to get you the information you need.<\/span><\/p>\n

Sulfamethoxazole-trimethoprim drug interactions<\/span><\/h2>\n

Many of the drug interactions related to sulfa-methoxazole-trimethoprim are related to magnifying the other med’s serious side effects. This comes as a result of SMX-TMP either increasing the other drug’s concentration or mechanism of action.<\/span><\/p>\n

Tikosyn<\/span><\/h3>\n

A classic double-edged sword, <\/span>dofetilide<\/span><\/a> is an antiarrhythmic, used for treating heart rhythm disorders, that can actually induce arrhythmias, even life-threatening ones, like Torsades de Pointes. Levels of the drug in our bloodstream play a role in determining how much adverse effect risk is present. Unfortunately, sulfamethoxazole-trimethoprim can increase Tikosyn levels in a dangerous fashion.<\/span><\/p>\n

Based on the high-risk nature of this interaction, it is usually best to avoid SMX-TMP when taking dofetilide. You should confirm this by speaking to the prescribing healthcare provider.<\/span><\/p>\n

Trexall<\/span><\/h3>\n

Trexall <\/span>(methotrexate)<\/span><\/a> is both a chemotherapeutic used in cancer treatment and a disease-modifying immunosuppressant agent used in treating autoimmune conditions like rheumatoid arthritis. While quite effective, methotrexate therapy must be closely monitored due to toxicities, <\/span>according to the Food and Drug Administration<\/span><\/a> (FDA). <\/span>SMX-TMP can increase the risk of methotrexate adverse reactions<\/span><\/a>, particularly when it comes to bone marrow suppression, which leads to anemia and low platelets (clotting cells). This issue might arise from folic acid inhibition, something methotrexate, sulfamethoxazole, and trimethoprim all do.<\/span><\/p>\n

Your doctor can talk to you about whether sulfamethoxazole-trimethoprim should be avoided altogether. If not, dosing may need to be modified or lab monitoring intensified. Looking for a different immunosuppressant to replace methotrexate could be difficult too, and keep in mind that cyclosporine, another drug used for autoimmune conditions, interacts with SMX-TMP too.<\/span><\/p>\n

Dilantin<\/span><\/h3>\n

Preventing seizures is obviously the foremost goal of epilepsy management. <\/span>Dilantin<\/span><\/a> can be quite effective at doing so, but to best balance this benefit with the ever-present risk of adverse effects, phenytoin dosing is carefully done utilizing blood level measurement. Those blood levels can spike with concurrent SMX-TMP use. The results can be perilous, including lethargy, confusion, and unsteadiness. Besides this direct interaction between the two meds, sulfamethoxazole, and phenytoin are among the highest-risk drugs for precipitating Stevens-Johnson syndrome, a serious drug reaction including skin rash.<\/span><\/p>\n

Combining phenytoin with sulfamethoxazole-trimethoprim may not be wise, and altering phenytoin dosing to permit the sulfa drug’s use could be risky as well. Reach out to your team of healthcare professionals about this interaction if you are prescribed both, and if you are feeling symptoms of this interaction, get medical care immediately.<\/span><\/p>\n

Jantoven<\/span><\/h3>\n

Jantoven <\/span>(warfarin)<\/span><\/a> thins the blood by blocking vitamin K from helping to build blood-clotting proteins. Since our vitamin K is mainly derived from good bacteria in our intestinal tract, it makes sense that antibiotics that kill those good bacteria will make warfarin’s anticoagulant job easier by reducing vitamin K supply. As a result, blood can become overly thin, leading to bleeding, when antibiotics are used with warfarin. Combination tablets of SMX and TMP are no exception to this rule. In fact, it might be the worst offender, because the combo may also boost warfarin concentrations in the body too. <\/span><\/p>\n

Excess bleeding risk is worrisome enough that finding an alternative to SMX-TMP may be worth your while. Your medical provider can guide you on finding an alternative antibiotic or reducing the dose of warfarin during your treatment course of sulfamethoxazole-trimethoprim.<\/span><\/p>\n

Oral hypoglycemics<\/span><\/h3>\n

Keeping blood glucose levels in check is a basic tenet of diabetes care. Of course, you want to make sure your sugar does not go too high, but just as importantly, you don’t want glucose levels to drop dangerously low. <\/span>Hypoglycemia<\/span><\/a> is a risk with some drugs for diabetes, most notably <\/span>insulin<\/span><\/a>, sulfonylureas, and <\/span>repaglinide<\/span><\/a>. By potentiating hypoglycemia, sulfamethoxazole with trimethoprim can make matters worse if you are taking sulfonylurea or repaglinide. Examples of sulfonylureas include:<\/span><\/p>\n