These antibiotics can increase levels of commonly used statins, or lipid-lowering drugs, to dangerous levels — a side effect due in part to the fact that both types of drugs interact with the same liver enzyme. The antibiotics actually slow down a liver enzyme (cytochrome P450 isoenzyme 3A4) so that it can no longer process statins, which then build up in the blood to toxic levels. Symptoms of toxicity include muscle aches, kidney injury, kidney failure, or worse: Toxicity can even be fatal.
A Close Look at Statin-Antibiotic Adverse Events
“I see patients who come in with kidney toxicity, and if there is harm, I want to bring attention to it,” says Amit X. Garg, MD, PhD, nephrologist and director of the London Kidney Clinical Research Unit of London Health Sciences Centre Victoria Hospital in London, Ontario, who was an author of two studies on the topic published in the February 2015 Canadian Medical Association Journal and the June 2013 Annals of Internal Medicine. Dr. Garg and colleagues combed through the medical and drug records of more than 144,000 Canadian patients ages 65 and up. They found that patients taking statins who were also prescribed the antibiotics clarithromycin or erythromycin were twice as likely to be hospitalized with muscle breakdown, called rhabdomyolysis. The relative risk of death at 30 days was one-and-a-half times higher for the older patients on statins who took clarithromycin or erythromycin. Patients taking statins and the antibiotic azithromycin, which works differently, didn’t experience this increased toxicity. “The interaction has been described in pharmacokinetic (the timing it takes for drugs to be processed by the body) studies, but this is the first population-based study looking at large numbers of patients,” Garg says. “To prevent these [drugs] from being prescribed together, we are making people aware of this issue.” Garg cautions that both prescriptions are frequently given to older patients. “Looking forward, statin prescriptions are very common," he says. “And clarithromycin and erythromycin are common antibiotics used to treat pneumonia, as well as upper respiratory and sinus infections.” “If an infection is not improving after a few days on an antibiotic, it can be because of reactions the patients are having, so they should get in touch with the prescribing physician,” Garg notes. But the drug toxicity that can occur with this combination of medicines is not necessarily cause and effect. Cardiologist Christopher P. Cannon, MD, senior physician at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School in Boston, cautions, “This is observational, so not definitive.”
Recognizing a Harmful Drug-Drug Interaction
How can a patient recognize the warning signs and symptoms of an adverse event from statin and antibiotic interactions? Garg explains that they’re difficult to pick up on. “Nonspecific symptoms like bad muscle aches occur with statin toxicity. And you often get these symptoms with a bad cold, so it’s hard to tell what’s what. But if somemeone comes in with statin toxicity, they are quite ill," says Garg. To look for the cause of symptoms, doctors check the kidneys, often the site of drug-drug interaction toxic effects. “We look at the kidney function — sometimes patients may need urgent dialysis.” Garg adds that patients often know what medication they took when they experienced a toxic drug-drug interaction, but in other cases the physician has to call the pharmacy to find out what was prescribed that could have been toxic. It’s important to be on the lookout for unusual symptoms that can indicate an adverse event from medication. “Muscle pains are usually the warning sign of rhabdomyolysis,” Cannon says. “Calling your doctor if you’ve just started a new medicine and you have a side effect would be the way to go.” RELATED: 10 Things Your Doctor Won’t Tell You About Hospital Infections
How to Avoid Drug Interactions With Statins
Which antibiotic you use makes a difference, and both doctors noted that azithromycin may be a safer choice for patients on statin medications. Azithromycin, sold under brand names including Zithromax, Zmax, or Z-Pak, is effective against infections like pneumonia and is usually given for five days. “There are many antibiotics that can be used for the same kinds of infections,” says Garg. An alternative is to suspend the statin medication only temporarily for the duration of the antibiotic prescription. “Statins can be stopped for 5 or 10 days and then restarted when the antibiotic is stopped,” Garg says. But getting back on statins is central to controlling cholesterol. “Statins have tremendous advantages, including survival advantage” in the long term, Garg notes. Computer order entry at the pharmacy is one of the advances that helps prevent drug-drug interactions for people with multiple conditions who are taking several drugs at once. A large number of prescriptions for antibiotics are inappropriate; for example, when you have a viral infection, an antibiotic won’t help. The best way to avoid a potentially toxic drug interaction is to not take antibiotics unless they’re really needed and likely to speed up your recovery. Be sure to talk to your doctor and pharmacist about all the drugs you’re taking to prevent harmful interactions from multiple prescriptions. “If a new med or antibiotic is used, it’s reasonable to ask if it will be okay with other medications," Cannon says.
