Macrolide allergy erythromycin

Erythromycin is a macrolide antibiotic isolated from Streptomyces erythraeus. It has a similar spectmm of activity to that of the early penicillins and was therefore often used as a substimte in patients who displayed life-threatening penicillin allergies. Erythromycin is a base, where the aliphatic tertiary amino group has a pKa of 8.8. Despite this, oral preparations are difficult to formulate because the tertiary alcohols at the 6 and 12 positions cause instability in stomach add. As with many tertiary alcohols in strong add, the C-OH bond can break to form highly reactive carbonium ions, in this case at dther the 6 or 12 positions. An intramolecular cydisation via the carbonyl oxygen at C-10 with the electrophilic carbonium ions results in formation of the inactive eiythralosamine (Fig. 8.15). 

Broad intravenous antibiotic coverage for the encapsulated organisms can include ceftriaxone or cefotaxime. For patients with true cephalosporin allergy, clindamycin may be used. If staphylococcal infection is suspected owing to previous history or the patient appears acutely ill, vancomycin should be initiated. Macrolide antibiotics, such as erythromycin and azithromycin, may be initiated if Mycoplasma pneumonia is suspected. While the patient is receiving broad-spectrum antibiotics, their regular use of penicillin for prophylaxis can be suspended. Fever should be controlled with acetaminophen or ibuprofen. Because of the risk of dehydration during infection with fever, increased fluid may be needed.6,27... 

Macrolides can be used in cases of intolerance, allergy, or contraindications to the use of tetracyclines (pregnancy, lactation, age <12 years). Erythromycin, clarithromycin, and azithromycin may be taken into consideration They inhibit neutrophil chemotaxis and the synthesis of pro-inflammatory cytokines. 

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