Methotrexate interaction with penicillin

Tetracycline Tetracycline injections have an acid pH. Incompatibility may reasonably be expected with alkaline preparations or with drugs unstable at low pH. Care should be taken when administering tetracyclines, since chelation takes place with metal ions. Tetracyclines interact with inorganic metal ions. They should not be used with drugs that cause hepatotoxicity and nephrotoxicity (e.g., digoxin, theophylline, ergot alkaloids, methotrexate, oral contraceptives, and penicillins). 

Interference with active transport. Organic acids are passed from the blood into the urine by active transport across the renal tubular epithelium. Penicillin is mostly excreted in this way. Probenecid, an organic acid that competes successfully with penicillin for this transport system, may be used to prolong the action of penicillin when repeated administration is impracticable, e.g. in sexually transmitted diseases, where compliance is notoriously poor. Interference with renal excretion of methotrexate by aspirin, of zidovudine by probenecid and of digoxin by quinidine, contribute to the potentially harmful interactions with these combinations. 

Clinically important, potentially hazardous interactions with amoxicillin, ampicillin, antacids, bacampicillin, calcium carbonate, carbenicillin, cloxacillin, digoxin, methotrexate, methoxyflurane, mezlocillin, nafcillin, oxacillin, penicillins, piperacillin, ticarcillin, zinc... 

Clinically important, potentially hazardous interactions with amphotericin B, benzodiazepines, doripenem, ertapenem, fludoxacillin, furosemide, glibenclamide, ketoprofen, ketorolac, methotrexate, NSAIDs, pemetrexed, penicillamine, penicillin G, penicillin V, salicylates, sulfamethoxazole, sulfonamides, torasemide, torsemide... 

Clinically important, potentially hazardous interactions with acitretin, aluminum hydroxide, amoxicillin, ampicillin, antacids, bacampicillin, betamethasone, bismuth, bromelain, calcium, carbenicillin, cholestyramine, doxacillin, corticosteroids, dairy products, dicloxacillin, didanosine, digoxin, food, glidazide, iron, isotretinoin, methicillin, methotrexate, methoxyflurane, mezlocillin, nafcillin, oxacillin, penicillins, piperacillin, retinoids, rocuronium, strontium ranelate, sucralfate, ticarcillin, vitamin A, zinc... 

METHOTREXATE PENICILLINS t plasma concentrations of methotrexate and risk of toxic effects of methotrexate, e.g. myelosuppression, liver cirrhosis, pulmonary toxicity Penicillins 1 renal elimination of methotrexate by renal tubular secretion, which is the main route of elimination of methotrexate. Penicillins compete with methotrexate for renal elimination. Displacement from proteinbinding sites may occur and is only a minor contribution to the interaction Avoid concurrent use. If concurrent use is necessary, monitor clinically and biochemically for blood dyscrasia, liver toxicity and pulmonary toxicity. Do FBCs and LFTs prior to concurrent treatment... 

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