Penicillins allergy types

Traditionally, high-dose penicillin G was the treatment standard for meningococcal disease. However, increasing penicillin resistance requires that third-generation cephalosporins now be used for empirical treatment until in vitro susceptibilities are known.23 Patients with a history of type I penicillin allergy or cephalosporin allergy may be treated with vancomycin. Treatment should be continued for 7 days, after which no further treatment is necessary. 

As such, patients with penicillin allergies should be treated with a first-generation cephalosporin (if non-type I allergy), a macrolide/azalide, or clindamycin. Recurrent infections caused by reinfection, poor adherence to therapy, or true penicillin failure can be treated with amoxicillin-clavulanate, clindamycin, or penicillin G benzathine.45... 

Cephalexin 250-500 mg 4 times daily 25-50 mg/kg per day in 4 doses 10 days Consider in penicillin allergy (if non-type I reaction)... 

Verify the patient s allergy history and the type of reaction experienced. Attempt to discern between true allergy and adverse event. (3-Lactam-allergic patients may receive clindamycin, vancomycin, or other antimicrobials. Crossreactivity between penicillin allergy and cephalosporins is low but cephalosporins should be avoided in patients with a history of anaphylaxis to penicillins. 

Establish the nature of the patient s penicillin allergy and if a history of type 1 hypersensitivity is suspected, suggest an alternative regimen to the clinician to incorporate MRSA cover such as vancomycin plus ciprofloxacin plus metronidazole. Do not delay treatment to allow time for a deep tissue specimen to be taken. 

Negligible cross-reactivity has been reported in both animal and human studies involving hapten inhibition, skin tests, and treatment of penicillin-allergic patients with therapeutic doses of aztreonam (12,14-19). Aztreonam therefore seems to be a safe alternative for patients with penicillin allergy. However, the numbers of safely treated patients reported are still small, and immediate type hypersensitivity to aztreonam has been reported in patients with penicillin allergy (20-23). 

Mechanisms of non-immediate reactions are unclear but may be immunological and non-immunological. Delayed reactions of the IgE type are known (131). Aminopenicillins seem to be an important cause of non-immediate reactions (132-134). The morbilliform rash that begins 1-10 days after amoxicillin can be caused by a delayed cell-mediated immune reaction (135) as can fixed drug eruptions (136,137), toxic epidermal necrolysis (138-140), bullous erythroderma (141), and contact eczema (142). Investigation of these disorders should include delayed readings of skin tests (135). In patients with chronic urticaria, penicillin allergy was demonstrated by cutaneous tests. 

H. C. Caldwell (to Lloyd Conover) Please discuss penicillin allergic-type reactions in the cephalosporins. Is there a crossover, and what is the prognosis for allergy-free cephalosporins ... 

Regarding in vitro tests, the RAST and ELISA deserve first mention. They are used mainly to detect IgE antibodies, though other types of antibodies can also be detected. The main usefulness of the tests lies in the field of allergy to inhalants but they can be used to detect drug allergies of typeticular penicillin allergies (Wide and Juhlin 1971). 

Wide L, Juhlin L (1971) Detection of penicillin allergy of the immediate type by radioimmunoassay of reagins (IgE) to penicilloyl conjugates. Clin Allergy 1 171 Wise F, Sulzberger MB (1933) Drug eruptions. I. Fixed phenolphthalein eruptions. Arch Dermatol 27 549... 

Experiments were performed with several drugs however, 15 cases of penicillin allergy were thoroughly studied according to the type of immune reaction. The result shown in Table 12 demonstrates a good correlation between the leukocyte mi-... 

Some types of allergic reaction, for example immediate or delayed-type skin allergies, serum-sickness-like reactions and anaphylactic reactions, may occur in a proportion of patients given penicillin treatment. There is some, but not complete, cross-allergy with cephalosporins. 

T cells control these learned responses and decide which tools to use in the reaction. Sometimes they choose several different tools at once, and multiple reactions ensue, such as when a person becomes sensitized to penicillin and has not only anaphylaxis but hemolytic anemia and serum sickness. There are different types of T cells, and they communicate either directly with other cells or by chemical messages called cytokines. The pattern of cytokines released is one way T cells have of determining which kind of response will occur. They are broadly called Thl andTh2 responses, with Thl mostly responding to infections and Th2 often producing allergy or asthma. 

If a patient has a mild, delayed allergy to penicillin, first-generation cephalosporins are effective alternatives but should be avoided in patients with an immediate-type hypersensitivity reaction. 

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