Drug Interaction Between Lipitor (Atorvastatin) And Z-Pak (Azithromycin)

The pharmacist discusses whether or not there is an interaction between Lipitor (atorvastatin) and azithromycin.

Jul 17, 2018

Beach Gal asked

How long after I am done taking my 6 azithromycin Tablets, 250 mg, can I go back to taking my Atorvastatin Tabs 80 Mg without being concerned about their being a drug interaction? I know this antibiotic stays in your system for awhile and wanted to make sure. Thanks for your help.

Answer

There is a potential risk of increased side effects if taking azithromycin with atorvastatin. This can cause an increased risk of rhabdomyolysis, a severe side effect that can be caused by atorvastatin. The potential interaction is well documented and The World Health Organization Adverse Drug Reaction database found a definitive association in increased risk with azithromycin and atorvastatin.


The half-life of azithromycin is long, around 68 hours. The half-life is the time it takes for 50% of the drug to be metabolized in our bodies and it generally takes around 5-6 half-lives for a drug to be completely eliminated. This means that it will take approximately 14 days for azithromycin to completely be eliminated from the system.


It isn't uncommon to take a short "break" on a "statin" drug like Lipitor if you were prescribed azithromycin but there are several factors to take into account. Discuss with your cardiologist or physician the best course of action to take in regards to this interaction. Read more about azithromycin and atorvastatin below.

 

Information About the Z-Pak

A Z-pak consists of six tablets of azithromycin 250 mg. Usually two tablets are prescribed on the first day of therapy, followed by one tablet for the following four days. Azithromycin is a macrolide antibiotic that can treat a variety of infections including bronchitis, sinus infections, ear infections, skin infections, sexually transmitted infections, and more. Azithromycin can cover several types of bacteria, but is not effective in treating the flu, the common cold, or other viral infections.


Like most antibiotics, azithromycin may cause diarrhea, nausea, vomiting, and abdominal pain. Macrolides are more likely to cause these types of side effects, but azithromycin is one of the more tolerable drugs in the class. Another concern with azithromycin is that it can cause QT prolongation in patients with a past medical history related to the heart. Drug interactions can also be a concern so always check each new medication prior to starting a new therapy.

 

Information About Lipitor

Lipitor (atorvastatin) is a statin medication, otherwise known as an HMG-CoA reductase inhibitor. Lipitor gradually decreases the amount of total cholesterol, LDL cholesterol (known as “bad” cholesterol), and triglycerides. Atorvastatin can reduce LDL levels by up to 45-60%. Atorvastatin 40-80 mg is considered a high intensity statin per the American College of Cardiology and American Heart Association.


Lipitor is metabolized by several processes, especially CYP3A4, P-glycoprotein, and OATP1B1. The most significant drug interactions with Lipitor come with medications that reduce or increase the activity of CYP3A4. CYP3A4 is the most common enzyme responsible for breaking down medications. Many drug interactions are due to inhibition or induction of CYP3A4 and other CYP enzymes.


Inhibiting the enzyme allows for drugs that require CYP metabolism to stay in the body longer at a higher concentration. Inhibitors can increase the effect of Lipitor, which may lead to side effects like muscle pain and a severe condition known as rhabdomyolysis. Examples of CYP3A4 inhibitors include diltiazem, digoxin, grapefruit, and many HIV medications. Azithromycin does not inhibit CYP3A4, but similar antibiotics clarithromycin and erythromycin do inhibit CYP3A4.


Per the Lipitor package insert, one study showed that drinking one glass of grapefruit juice (8 ounces) with atorvastatin resulted in an increased drug concentration of 37%. Drinking excessive amounts of grapefruit (approximately 1 L/day) increased drug concentrations 250%. Avoid grapefruit juice to avoid risk of side effects. 

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