Thursday, August 24, 2023

Methotrexate and Anbx

Q: 58 years old female with rheumatoid arthritis is admitted to ICU with community-acquired pneumonia. Home medications include Methotrexate. Which group of antibiotics should be preferably avoided?

A) Fluoroquinolone
B) Penicillin


Answer: B

Penicillin has been shown to compete with the renal tubular secretion of methotrexate and hence its clearance when co-prescribed. Concurrent use of methotrexate and penicillin may increase the toxicity of methotrexate, particularly neutropenia.

Similar effects are reported from Bactrim.


#pharmacology



References: 

1. Methotrexate induced neutropenia associated with coprescription of penicillins: serious and under-reported? - Rheumatology 2006 45(3):361-362

2. Pharmacokinetic interaction between methotrexate and piperacillin/tazobactam resulting in prolonged toxic concentrations of methotrexate - Journal of Antimicrobial Chemotherapy 2006 58(1):228-230

3. Methotrexate-induced pancytopenia associated with co-prescription of penicillin and trimethoprim Clinical Rheumatology, Volume 26, Number 1, January 2007 , pp. 134-135(2)

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