Key takeaways:
Bactrim is an antibiotic that combines the medications sulfamethoxazole and trimethoprim.
The medications work together to fight infections.
This antibiotic is commonly prescribed for things like urinary tract infections or ear infections.
Save on related medications
If you have a bacterial infection, your provider may prescribe an antibiotic.
Bactrim is a brand-name for a commonly prescribed antibiotic that is a combination of two medications — trimethoprim and sulfamethoxazole. Another common brand-name is Septra.
Bactrim works by killing bacteria. It treats common bacterial infections like urinary tract infections (UTIs), ear infections, and bronchitis.
Bactrim is also used off-label for other types of infections, including skin infections. This is especially true if a certain type of bacteria, called methicillin-resistant Staphylococcus aureus (MRSA) is suspected. Bactrim is a first-choice antibiotic to treat MRSA skin infections.
What’s it like to take Bactrim for a bacterial infection? Here’s how a couple of people describe it.
Mild side effects can include nausea
Victoria Hable, a 27-year-old graduate student in Mechanicsburg, Pennsylvania, took Bactrim to help treat infection from cysts around the hair follicles on her scalp. She developed this problem after having hair extensions. The antibiotic worked, but she also experienced a common side effect from the medication: nausea.
“It was stressful to be nauseous with needing to get things done as a busy grad student and single mom,” Victoria says. “It didn’t make me feel great, but it did clear up the infection and blisters on my scalp very quickly.”
She says her discomfort wouldn’t keep her from taking it again.
“If you can deal with the side effects, it does work fast and is a strong antibiotic,” she says.
It’s not the only antibiotic available
Leah Kneppar, a 34-year-old nurse in Leonardtown, Maryland, took Bactrim to treat a UTI.
While she didn’t experience any side effects, her UTI returned.
“Unfortunately, the bacteria was not susceptible to Bactrim. Once the culture and sensitivity returned, I was placed on a different antibiotic for the specific bacteria.” Leah says.
While Bactrim is one of the most commonly prescribed antibiotics used to treat UTIs, it’s not the only one. For Leah, a different antibiotic worked better.
But she says she would take Bactrim again if her provider prescribed it for something other than a UTI.
“It seems the bacteria my bladder likes to propagate is never sensitive to Bactrim,” Leah says. “But if I ever do have a Bactrim-sensitive bug, I would take it again.”
What does the pharmacist say?
Amy Gragnolati, PharmD
Pharmacy editor
Bactrim is a common antibiotic that treats many bacterial infections. It combines two antibiotics called sulfamethoxazole and trimethoprim. It’s FDA-approved to treat:
UTIs
Ear infections in kids
Chronic bronchitis flare-ups
Traveler’s diarrhea
Pneumonia in people whose immune systems don’t work as well as they could (immunocompromised)
Diarrhea caused by Shigella bacteria
Bactrim works by killing bacteria. And it works quickly — it can begin to kill bacteria within 1 to 4 hours of taking it. So, you may start to feel relief within a few days for infections like a UTI. But for more serious infections, like pneumonia, it may take a couple weeks to feel an improvement.
It’s important to finish the entire course of Bactrim that’s prescribed to you, even if you start to feel better before you finish. Bacteria may still be left in your body even as your symptoms improve. If you don’t kill all the bacteria, it can become resistant to some antibiotics and harder to treat.
Bactrim is convenient for many people because it’s available as a pill, oral liquid, and injection. It comes as a cheaper generic product and can be taken with or without food. But if you experience nausea after taking it, try taking it with food.
Besides nausea, common side effects of Bactrim include diarrhea, loss of appetite, and skin reactions. Bactrim can also make you more sensitive to the sun, so make sure to avoid sun exposure and wear sunscreen with an SPF of at least 30 while taking Bactrim.
More serious Bactrim side effects include severe allergic or skin reactions, low platelets, and severe diarrhea that can cause dehydration. It can also cause low blood sugar and kidney stones. Pregnant women shouldn’t take Bactrim because it can cause birth defects in an unborn baby.
Before starting Bactrim, give your healthcare provider and pharmacist a list of all the medications and supplements you take. Bactrim can have many drug interactions. Your provider or pharmacist can help you check whether any of your other medications might interact with Bactrim.
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