A new cocktail mixing commonly used antibiotic with common blood pressure medications can be extremely harmful to persons over age 65. Hypotension and shock was found to occur in a significant percentage of subjects studied over 15 year period.
A study was conducted in Canada amongst Ontarians 65 years plus, who were treated with calcium-channel blockers which are often used to treat high blood pressure. The most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with hypertension, with particular efficacy in treating elderly patients. Also, calcium channel blockers frequently are used to control heart rate, prevent cerebral vasospasm, and reduce chest pain due to angina pectoris.
Researchers identified 7100 patients hospitalized for low blood pressure or shock while taking a calcium channel blocker. Treatment with erythromycin was found to increase the risk of low blood pressure almost 6-fold, while clarithromycin increased the risk almost 4-fold. In contrast, azithromycin did not increase the risk of hypotension.
Dr. David Juurlink, Scientist at the Sunnybrook Research Institute and the Institute for Clinical Evaluative Sciences states:
“Macrolide antibiotics (erythromycin, clarithromycin and azithromycin) are among the most widely prescribed antibiotics, with millions of prescriptions dispensed in Canada each year. The drugs are generally well-tolerated, but they can cause several important drug interactions. In older patients receiving calcium channel blockers, the two macrolide antibiotics erythromycin and clarithromycin are associated with a major increase in the risk of hospitalization for hypotension. However, the related drug azithromycin appears safe. When clinically appropriate, it should be used preferentially in patients receiving a calcium channel blocker.”
Antibiotic macrolides are used to treat infections caused by Gram positive bacteria, Streptococcus pneumoniae, and Haemophilus influenza infections such as respiratory tract and soft tissue infections. The antimicrobial spectrum of macrolides is slightly wider than that of penicillin, and, therefore, macrolides are a common substitute for patients with a penicillin allergy.
Beta-hemolytic streptococci, pneumococci, staphylococci, and enterococci are usually susceptible to macrolides. Unlike penicillin, macrolides have been shown to be effective against mycoplasma, mycobacteria, some rickettsia, and chlamydia.
This issue also spreads across the southern border to the United States. Prices of brand name drugs in the United States are significantly higher than in Canada, India, the UK and other countries, nearly all of which have price controls. The price differential for brand-name drugs between the U.S. and Canada has led Americans to purchase more than $1 billion USD in drugs per year from Canadian pharmacies.
Source: CMAJ
Written By Sy Kraft, B.A.