Millions of Americans take statins daily to lower their cholesterol levels. New research shows that taking an antibiotic at the same time may have dangerous effects on your kidneys.

A recent study in the Canadian Medical Association Journal (CMAJ), published December 22, looked at a population of older adults and the impact of Clarithromycin (Biaxin) vs Azithromycin (Zithromax, or Z-pak) in combination with other statins, and found that some combinations may increase the risk for kidney injuries. Azithromcyin is also linked to an increased risk of sudden heart attack, liver injury, and other antibiotic side effects.

The research, performed at Western University in London, Canada by Dr. Amit Garg and colleagues, looked at the connection between antibiotics, statins and the frequency of serious adverse events. Studying a population of adults with a mean age of 74 years who were taking a statin not metabolized by cytochrome P450 3A4 (CYP3A4).

CYP3A4, according to Wikipedia, “is an important enzyme in the body, mainly found in the liver and in the intestine. Its purpose is to oxidize small foreign organic molecules (xenobiotics), such as toxins or drugs, so that they can be removed from the body.”

Researchers looked at three cholesterol-fighting statins (Crestor, Lescol and Pravachol) that past studies showed to be safer in combination with clarithromycin. Scientists then compared reactions of those individuals when using antibiotics with their statin, analyzing “existing data on 104,041 statin users in Ontario, Canada, between 2002 and 2013,” half who were given Biaxin and the other half Zithromax.

Outcomes were assessed within 30 days of the patient starting the antibiotic. What researchers found was that taking clarithromycin at the same time as a statin that is not metabolized by CYP3A4 showed an increased frequency of unfavorable events, such as acute kidney injury, hyperkalemia (dangerous levels of potassium in the blood), or rhabdomyolysis (a condition wherein damaged muscle tissue breaks down, releasing potentially harmful cells into the bloodstream that can harm the kidneys).

Statistically, in this study, 13 patients on clarithromycin were hospitalized with rhabdomyolysis, compared to six azithromycin users; 175 patients taking clarithromycin were hospitalized with acute kidney injury, versus 122 in the azithromycin group; and 33 Biaxin users were hospitalized with hyperkalemia in comparison to 18 Zithromax users. “Overall, 200 of the clarithromycin patients and 155 azithromycin patients had fatal complications.”

While the overall increase in risk is small, it is worthy to note. It is also not the only risk with antibiotics like Zithromax.

Zithromax and Antibiotic Risks

Zithromax, manufactured by Pfizer, is a popular drug due to its shorter prescription period. Unlike the 10-day to two-week cycles of many antibiotics, Zithromax has a five- to seven-day cycle. However, it does have a longer half-life in the body.

Zithromax belongs to a family of antibiotics called macrolides. Macrolides are bacteriostatic, treating infections “by preventing bacteria from multiplying and producing the proteins that are essential for their growth.” The other type of antibiotic is bactericidal, killer of the bacteria itself.

Azithromycin, like other macrolide antibiotics, has been linked to hepatotoxicity (chemical-caused liver damage). Moreover, patient requests for the popular drug and overprescribing have led to many Zithromax-induced adverse injury reports. Because azithromycin has become so commonly used, it has become noted as one of the more common causes of drug induced liver injury. It has also been purported that for individuals with existing heart issues, Zithromax is a particularly high-risk medication; other claims detail rare occurrences of liver failure and Stevens Johnson Syndrome (SJS).

Victims of these incidents, and plaintiffs in Zithromax class action lawsuits against Pfizer, say that the Z-Pak label carries insufficient warnings of these risks.