Ampicillin and Cefoxitin interaction
Ampicillin and Cefoxitin: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Ampicillin label · effective 2026-07-27
CONTRAINDICATIONS The use of Ampicillin is contraindicated in individuals with a history of serious hypersensitivity reactions (e.g., anaphylaxis or Stevens-Johnson syndrome) to ampicillin or to other beta-lactam antibacterial drugs.
THERE HAVE BEEN REPORTS OF INDIVIDUALS WITH A HISTORY OF PENICILLIN HYPERSENSITIVITY WHO HAVE EXPERIENCED SEVERE REACTIONS WHEN TREATED WITH CEPHALOSPORINS.
BEFORE THERAPY WITH ANY PENICILLIN, CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS OR OTHER ALLERGENS.
From the Cefoxitin (Cefoxitin and Dextrose) label · effective 2019-07-29
Hypersensitivity to cefoxitin or other beta-lactam antibacterial drugs.
Hypersensitivity to Cefoxitin or other Beta-lactam Antibacterial Drugs Cefoxitin for Injection and Dextrose Injection is contraindicated in patients who have shown hypersensitivity to cefoxitin or to other β-lactam antibacterial drugs (e.g., penicillins and cephalosporins).
Hypersensitivity Reactions to Cefoxitin or other Beta-lactam Antibacterial Drugs Serious and occasionally fatal hypersensitivity reactions (e.g., anaphylaxis) have been reported in patients on β-lactam antibacterials, including cefoxitin [see Adverse Reactions (6.1) ] .
There have been reports of individuals with a history of penicillin hypersensitivity who have experienced severe reactions when treated with cephalosporins.
Before initiating therapy with Cefoxitin for Injection and Dextrose Injection, inquire about previous hypersensitivity reactions to penicillins, cephalosporins, or other allergens.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.