Hypersensitivity reactions to penicillins

Generally reserved for patients with hypersensitivity reactions to penicillin. 

Vancomycin is effective and is the drug of choice for the patient with a history of immediate-type hypersensitivity reaction to penicillin. When vancomycin is used, the addition of gentamicin is not recommended. 

Penicillin G 24 million units/24 h IV in four to six equally divided doses may be used in place of nafcillin or oxacillin if strain is penicillin susceptible (minimum inhibitory concentration 0,1 mcg/mL) and does not produce /5-lactamase vancomycin should be used in patients with immediate-type hypersensitivity reactions to beta-lactam antibiotics (see Table 37-3 for dosing guidelines) cefazolin may be substituted for nafcillin or oxacillin in patients with non-immediate-type hypersensitivity reactions to penicillins... 

Weiss, M.E. and Adkinson, N.F., Immediate hypersensitivity reactions to penicillin and related antibiotics, Clin. Allergy, 18, 515, 1988. 

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. 

Because of potential toxicity, bacterial resistance, and the availability of many other effective alternatives, chloramphenicol is rarely used. It may be considered for treatment of serious rickettsial infections such as typhus and Rocky Mountain spotted fever. It is an alternative to a B-lactam antibiotic for treatment of meningococcal meningitis occurring in patients who have major hypersensitivity reactions to penicillin or bacterial meningitis caused by penicillin-resistant strains of pneumococci. The dosage is 50-100 mg/kg/d in four divided doses. 

Hypersensitity reaction in patients with hypersensitivity reactions to penicillins, the incidence of cross-reactivity to carbapenems is 50%. 

Immediate hypersensitivity reactions to penicillin are rare after a properly performed negative skin test when both major and minor determinants are used. Dermatologic reactions occur in 1% of skin-test-negative patients. A negative penicillin skin test indicates... 

Patients with delayed reactions to penicillin (skin rash) generally can receive cephalosporins. Patients with type I hypersensitivity reactions to penicillins (anaphylaxis) should not receive cephalosporins or carbapenems (alternatives include aztreonam, quinolones, sulfa drugs, or vancomycin based on type of coverage indicated). 

If a patient has a mild, delayed allergy to penicillin, first-generation cephalosporins (such as cefazolin) are effective alternatives, but they should be avoided in patients with a history of immediate-type hypersensitivity reactions to penicillins (see Table 109-6). The potential for a true immediate-type allergy should be assessed carefully, and a penicillin skin test should be conducted before giving antibiotic treatment to any patient claiming an allergy. 

Adverse reactions to penicillins are rare diarrhoea can occur due to alteration in normal gastrointestinal bacteria. In fact, penicillins are probably the least toxic drugs known. Hypersensitivity reactions to penicillins occur in up to 10% of patients and vary from mild skin rashes to exfoliative dermatitis and Stevens-Johnson syndrome (immune vasculitis with arthritis, nephritis, central nervous system abnormalities and myocarditis) and from bronchoconstriction to life-threatening anaphylactic shock. 

In humans, sensitization and subsequent hypersensitivity reactions to penicillin are relatively common during treatment. By comparison, adverse reactions attributed to occupational exposure to penicillin or the ingestion of food containing residues of penicillin are now seldom reported. 

The incidence of hypersensitivity reactions to penicillins is about 1-2 % but, importantly, up to about 10 % of patients taking a penicillin report. 

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