A study has been able to establish that giving a definite antibiotic to elderly patients, already taking generally prescribed cardiovascular drugs can be dangerous.

The study found that taking trimethoprim-sulfamethoxazole on top of ACEIs or ARBs tends to lead to an almost seven-fold heightened risk of hospitalization in contrast to other antibiotics.

TMP-SMX if taken along with one of the other two classes of drugs can cause unusually high levels of potassium in the blood, which is a condition called hyperkalemia.

ACEI, which stands for, angiotensin, converting enzyme inhibitors, and ARBs - angiotensin receptor blockers are used by a great mass of populace, throughout the world to treat high blood pressure, kidney disease and heart failure.

Hyperkalemia is a potentially hazardous side-effect of these drugs, since it can lead to heart rhythm turbulence.

The 1994-2008 study of Ontarians aged 66 years or older found that approximately 12% of patients were given a minimum of one prescription for TMP-SMX, whilst on ACEI or ARB therapy.

The study offers confirmation of a potentially dangerous interaction, between varieties of very commonly used drugs, stated lead Author, Tony Antoniou of the Institute for Clinical Evaluative Sciences.

Physicians and pharmacists should know about the potential for this interaction and, if probable, select substitute antibiotics that do not interact with ACEI or ARBs.