Taking spironolactone, a water pill, alongside the antibiotic trimethoprim-sulfamethoxazole can cause blood potassium to rise to potentially life-threatening levels. Researchers from St. Michael’s Hospital in Toronto combined information to track over 206,000 patients aged 66 or older who were treated with the water pill spironolactone. Over a 17-year period, almost 12,000 people died suddenly — 349 of them within 14 days after taking either trimethoprim-sulfamethoxazole or another antibiotic. Via CBS News. Posted February 2, 2015.