Sulfa antibiotics such as Bactrim are one of the most commonly prescribed types of antibiotics to treat a variety of infections – from urinary tract infections to bronchitis. Most people tolerate these antibiotics well, but a new study raises some concerns that Bactrim and other sulfa antibiotics could raise potassium levels to dangerous levels. This previously unrecognized side effect is concerning since high potassium levels are associated with irregular heart rhythms and even death.
Elevated Potassium Level with Sulfa Antibiotics?
Researchers looked at 300,000 older people in Canada who were taking a class of medications used to treat hypertension called beta-blockers. After reviewing their charts, they found 189 of these mature adults went on to develop very high potassium levels after taking a sulfa antibiotic – giving rise to concerns that sulfa antibiotics can adversely affect potassium levels. They don’t believe the interaction between sulfa antibiotics and beta-blockers accounts for the elevated potassium levels seen in these older people.
How might sulfa antibiotics cause elevated potassium levels? Researchers believe these medications prevent the removal of potassium from the body by the kidneys. This causes potassium to build up to dangerous levels which could be fatal. Since this study was done on older adults, it’s not clear whether the same risk would be seen in younger people with better kidney function.
Other Side Effects of Bactrim and Sulfa Antibiotics
Sulfa antibiotics, like Bactrim, can have other serious side effects too. In rare cases, a sometimes fatal skin condition called Stevens-Johnson syndrome develops, and they can, rarely, cause a serious form of anemia called aplastic anemia – as well as damage to the liver or lungs. Other side effects of Bactrim include nausea, headache, cough, fever, or fever. Alcohol should never be used when taking sulfa antibiotics as it increases the risk of serious side effects.
Sulfa Antibiotics and Elevated Potassium Levels: The Bottom Line
Since this is a relatively new finding, more studies are needed. In the meantime, it would be wise to consider another class of antibiotic – if possible. People who have kidney disease, diabetes, or other conditions that can alter potassium balance should stay away from sulfa antibiotics entirely until more is known. Talk to your doctor about this.