Taking Methotrexate With Azithromycin

Lulu asked

I take an injection of methotrexate once a week. I got sick last week when I had my injection on Thursday, and on Friday, I started a five-day dose of azithromycin. Is this dangerous? I have finished the azithromycin, but do I need to hold my methotrexate injection tomorrow?

Answer

There is some concern with using methotrexate and azithromycin together, but overall, the combination is relatively safe to use in certain situations.

The two main concerns are:

• Increases in liver enzymes
• Increase in methotrexate concentrations

I discuss each of these in more detail below.

Liver Enzymes

Both azithromycin and methotrexate are metabolized through the liver and both have been reported to cause increases in certain liver enzymes.

The prescribing information for azithromycin states the following:^[1]

Abnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported, some of which have resulted in death. Discontinue azithromycin immediately if signs and symptoms of hepatitis occur.

Side effects involving the liver with azithromycin use are uncommon, however.

In clinical trials for the drug, elevated liver enzymes occurred in 4—6% of individuals receiving intravenous therapy. In those taking the drug orally, only 1—2% experienced an increase in liver enzymes. Severe side effects, like liver failure, are thought to be exceedingly uncommon and there are generally other predisposing factors in play.^[2]

Methotrexate is more often associated with impaired liver function than azithromycin. Per the prescribing information:^[3]

Transient liver function test abnormalities are observed frequently after methotrexate administration and are usually not cause for modification of methotrexate therapy. Persistent liver function test abnormalities, and/or depression of serum albumin may be indicators of serious liver toxicity and require evaluation.

In those taking methotrexate for extended periods of time, periodic liver function tests are recommended (about every one or two months).

Since both azithromycin and methotrexate could potentially cause liver dysfunction, caution is recommended when using them together.

Nevertheless, the concern here is generally in those who already have some sort of liver problem, or are taking additional drugs that may affect liver function.

Methotrexate Levels

Some sources state that azithromycin can increase concentrations of methotrexate in the body if taken together.

Our own interaction checker, which pulls data from DrugBank, reports the following:^[4]

The serum concentration of Methotrexate can be increased when it is combined with Azithromycin.

This is based on the fact that both methotrexate and azithromycin are metabolized through the liver. Therefore, if used together, the liver may not be able to process them as efficiently. Additionally, if azithromycin alone causes liver dysfunction, methotrexate metabolism may be compromised.

Increases in methotrexate concentrations could theoretically increase the incidence of side effects.

Although azithromycin increasing methotrexate concentrations is possible, it hasn't been seen in clinical studies.

In fact, studies that specifically look into interactions concerning azithromycin and methotrexate don't list them as interacting agents.^[5][6]

Final Words

While there is a concern with using azithromycin and methotrexate together, it is mostly based on whether or not either affects liver function.

Use of both in those with normal liver function generally shouldn't cause significant problems, but your liver function should be monitored periodically, especially if you are taking one or both on a long term basis.

Be sure to speak with your doctor regarding any concerns you have regarding the use of methotrexate and azithromycin together. You shouldn't alter your medication regimen at all without first talking with your doctor.