Antibiotics & blood pressure i recently was treated for a kidney/bladder infection with sulfameth/tri 800/160. in an emerg. clinic. just prior to that, my pc doctor had increased my lisinopril from 20mg/day to 40mg/day because my bp was up during an of

The : The trimethoprim-sulfamethoxazole antibiotic should not significantly affect the potency of your Lisinopril dose with regard to its blood pressure effect. The combination of these two drugs can increase the risk of hyperkalemia, which is too much potassium in the blood stream, but this doesn't impact your bp. There are a few reasons that could explain why your blood pressure fell, the most likely being that your higher Lisinopril dose was working as intended. Keep in mind that your doctor doubled your Lisinopril dose in response to high blood pressure, and your BP fell appropriately. If the drop was too great, then it may be that you need an intermediate dose (e.g. 30 mg/day). It is also possible that it was the infection (not the antibiotic) that was lowering your blood pressure. When the body is infected, substances are released that result in lowered bp. No matter the reason, it will be important to follow your BP over the next few weeks because it is possible that you really do need the higher dose of lisinopril. Currently, your BP is great but it could increase again now that the infection has cleared and you are back on the lower dose of lisinopril.

See below: Sometimes the combination of Lisinopril and Bactrim (sulfamethoxazole and trimethoprim) can cause high potassium levels particularly in certain conditions- your doctor will be aware of that.