INFO - Antibiotics and methotrexate

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DermNet NZ

Last updated 13 Apr 2008

Excerpt:

Other medicines may interfere with methotrexate.

Many medications may result in an increase in side effects or a

decrease in the effectiveness of methotrexate or the other drug. Tell

your doctor all the medicines you are taking, whether they are

prescription or non-prescription medicines. If you are having an

operation with a general anaesthetic, tell the anaesthetist you are on

methotrexate.

Do not begin or change the dosage of any medicine without first

checking with your doctor. This is especially true of antibiotics and

anti-inflammatory agents.

Like methotrexate, antibiotics that contain the drug trimethoprim or

cotrimoxazole antagonise folate. Taking them at the same time as

methotrexate could result in unexpected and dangerous toxicity.

Aspirin and aspirin-like drugs (nonsteroidal anti-inflammatory

medicines) may reduce how much methotrexate is eliminated by the

kidneys. This could potentially result in a toxic build-up of

methotrexate in the blood stream. Anti-inflammatories can often be

taken safely but you should have regular blood tests if you start

these medicines or others, as advised by your doctor. Alternatively,

you could take paracetamol (acetominophen), as this does not interfere

with methotrexate.

Live vaccines may be ineffective in those taking methotrexate or cause

allergic reactions.

http://dermnetnz.org/treatments/methotrexate.html

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RxList.com

Trexall (methotrexate)

Excerpt:

Methotrexate is partially bound to serum albumin, and toxicity may be

increased because of displacement by certain drugs, such as

salicylates, phenylbutazone, phenytoin, and sulfonamides. Renal

tubular transport is also diminished by probenecid; use of

methotrexate with this drug should be carefully monitored. Oral

antibiotics such as tetracycline, chloramphenicol, and nonabsorbable

broad spectrum antibiotics, may decrease intestinal absorption of

methotrexate or interfere with the enterohepatic circulation by

inhibiting bowel flora and suppressing metabolism of the drug by

bacteria.

Penicillins may reduce the renal clearance of methotrexate; increased

serum concentrations of methotrexate with concomitant hematologic and

gastrointestinal toxicity have been observed with high and low dose

methotrexate. Use of methotrexate with penicillins should be carefully

monitored.

The potential for increased hepatotoxicity when methotrexate is

administered with other hepatotoxic agents has not been evaluated.

However, hepatotoxicity has been reported in such cases. Therefore,

patients receiving concomitant therapy with methotrexate and other

potential hepatotoxins (e.g., azathioprine, retinoids, sulfasalazine)

should be closely monitored for possible increased risk of

hepatotoxicity. Methotrexate may decrease the clearance of

theophylline; theophylline levels should be monitored when used

concurrently with methotrexate.

http://www.rxlist.com/cgi/generic/mtx_ad.htm

Not an MD