Doxycycline Methotrexate

These include mesalazine, metformin, NSAIDs, tetracyclines (except doxycycline and minocycline), chloramphenicol, lithium, methotrexate, chloroquine, fibrates, chlorpropamide and glibenclamide, Clinically, it is useful to measure urine output per hour or per 24 hours as a fall in urine output in the presence of adequate fluid intake often indicates or warns of some impairment of renal function. Furthermore, it is neither expensive nor time-consuming to perform a quick test for albumin, casts and red cells in the urine, and to measure pH. Creatinine clearance values are often used to determine the safe doses for several drugs (e.g. NSAIDs, ciclosporin). 

Doxycycline can be added to the long list of drugs (SEDA-18, 262) (SEDA-23, 253) that can interact with methotrexate (20). 

A 17-year-old girl with a femoral osteosarcoma received her 11th cycle of methotrexate and simultaneously oral doxycycline 100 mg bd for a palpebral abscess. As in previous cycles, pharmacokinetic monitoring of methotrexate was performed. On this occasion the half-life of methotrexate was more than doubled. She developed hematological and gastroenterological toxicity. 

The authors recommended that in patients receiving methotrexate an alternative to doxycycline should be used. 

Tortajada-Ituren JJ, Ordovas-Baines JP, Llopis-Salvia P, Jimenez-Torres NV. High-dose methotrexate-doxycycline interaction. Ann Pharmacother 1999 33(7-8) 804-8. 

Clinically important, potentially hazardous interactions with allopurinol, anticoagulants, chloramphenicol, cyclosporine, demeclocycline, doxycycline, erythromycin, methotrexate, minocycline, oxytetracycline, sulfonamides, tetracycline... 

Clinically important, potentially hazardous interactions with anisindione, anticoagulants, atracurium, cisatracurium, demeclocycline, dicumarol, doxacurium, doxycycline, imipenem/cilastatin, methotrexate, minocycline, non-depolarizing muscle relaxants, oxytetracycline, pancuronium, rapacuronium, reteplase, tetracycline, warfarin... 

Iven H, BraschH. Influence of the antibiotics piperacillin, doxycycline, and tobramycin on the pharmacokinetics of methotrexate in rabbits. Cancer ChemoAer Phamacol (i9Z6) 17, 218-22. 

Two case reports describe the development of methotrexate toxicity in patients also given tetracycline or doxycycline. 

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