Drug cross hypersensitivity penicillin, cephalosporin

In some patients, cephalosporins may cause an allergic reaction similar to the penicillin hypersensitivity described previously. A cross-sensitivity often exists a patient who is allergic to penicillin drugs will also display hypersensitivity to cephalosporin agents. Other principal adverse effects of cephalosporins include gastrointestinal problems such as stomach cramps, diarrhea, nausea, and vomiting. 

Hypersensitivity reactions (2% incidence) wide range, but rashes and drug fever most common, positive Coombs test, but rarely hemolysis. Assume complete cross-allergenicity between individual cephalosporins and partial cross-hypersensitivity with penicillins (about 5%). Most authorities recommend voiding (iTffl S()[ >1.cephalosporins in patients allergic to penicillins (tor gram-positive organism ... 

Hypersensitivity reactions Make careful inquiry for a history of hypersensitivity reactions. Monitor patients who have had immediate hypersensitivity reactions to penicillins or cephalosporins. If an allergic reaction occurs, discontinue the drug and institute supportive treatment. Cross-sensitivity with other penicillins or -lactam antibiotics is rare. 

Cephalosporins are sensitizing and may elicit a variety of hypersensitivity reactions that are identical to those of penicillins, including anaphylaxis, fever, skin rashes, nephritis, granulocytopenia, and hemolytic anemia. However, the chemical nucleus of cephalosporins is sufficiently different from that of penicillins so that some individuals with a history of penicillin allergy may tolerate cephalosporins. The frequency of cross-allergenicity between the two groups of drugs is uncertain but is probably around 5-10%. However, patients with a history of anaphylaxis to penicillins should not receive cephalosporins. 

The cephalosporins are contraindicated in patients with known allergies or intolerances to any of the cephalosporins. Because the penicillins and cephalosporins have a common chemical structure, cross-allergies occur with these drugs. Thus before initiating therapy with a cephalosporin, careful inquiry should be made concerning previous hypersensitivity reactions to the other drugs. Because a secondary vitamin K deficiency can develop with cephalosporin use, the cephalosporins are contraindicated in patients with hemophilia. Cefaclor is also contraindicated in any patient with previous drug-related joint and skin reactions. 

ADVERSE REACTIONS Hypersensitivity reactions are the most common side effects of cephalosporins they are identical to those caused by the penicillins, perhaps related to their shared /3-lactam structure. Patients who are allergic to one drug class may manifest cross-reactivity to a member of the other class. There is no skin test that can reliably predict whether a patient will manifest an allergic reaction to the cephalosporins. 

Each of the dmgs listed has activity against some gram-negative bacilli. All penicillins should be avoided in patients with a history of allergic reactions to any individual penicillin drug. Cephalosporins should also be avoided in patients who have had anaphylaxis or other severe hypersensitivity reactions following use of a penicillin. There is no cross-reactivity between the penicillins and aztreonam. The answer is (B). 

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