Antibiotics, especially the penicillin and sulfonamides account for a large proportion of allergic drug reactions
Risk factors: Risk factor for clinical expression of antibiotic allergy includes:
Route of administration (e.g. allergic reactions to penicillin occur more frequently following parenteral rather than oral administration)
Previous exposure (which may have non-therapeutic e.g. in utero, food product)
Ages between 20 and 49 (children and elderly are at lower risk.
Classification: Allergic reactions to antibiotics can generally be classified according to their time of onset. The diagnosis of antibiotics allergy is rarely clear-cut. It is often not clear whether the symptoms are due to the patient’s underlying condition or the treatment. For example rashes may be caused by the underlying infection or occur as a result of antibiotic allergy. The problem becomes even more complicated when the patient is taking more than one drug. The history of the events surrounding the onset of the adverse reaction is often most important.
Laboratory diagnosis: There is no single test for antibiotic allergy a basic problem in diagnosing antibiotic allergy; a basic problem in diagnostic antibiotics allergy by immunological methods is the fact that most antibiotics are not complete antigens but rather haptenic metabolites of the parent drug coupled with a carrier tissue protein. With exception of penicillin immuno-reactive drug metabolites have rarely been identified.
Both skin prick and allergen specific IgE (RAST) test can be performed. RAST tests are less sensitive and give less information than skin testing to penicillin allergens. In general, RAST testing should only be used in patients who cannot be skin tested.
Skin testing for antibiotics allergy: Skin testing is of definite value in assessing hypersensitivity to certain antibiotics primarily penicillin, but is not helpful in predicting reactions caused by IgE antibiotics. Skin testing should only be performed by specialists due to risk of anaphylaxis. Most non-pruritic maculopapular rashes will not be predicted by skin testing.
Semi synthetic such as ticarcillin and piperacillin contain same nucleus as penicillin G hence sensitivity to these antibiotics can be assessed by skin testing to penicillin as well as the parent drug. Cephalosporin share a common beta-lactam ring with the penicillin but the degree of cross-reacting is quite low. Mon bactams such as aztreonam may be safely administered to penicillin allergic subjects by carbapenems such as imipenem represents as a significant risk to penicillin-allergic patients and should be withheld from penicillin skin test positive patients.
Risk factors: Risk factor for clinical expression of antibiotic allergy includes:
Route of administration (e.g. allergic reactions to penicillin occur more frequently following parenteral rather than oral administration)
Previous exposure (which may have non-therapeutic e.g. in utero, food product)
Ages between 20 and 49 (children and elderly are at lower risk.
Classification: Allergic reactions to antibiotics can generally be classified according to their time of onset. The diagnosis of antibiotics allergy is rarely clear-cut. It is often not clear whether the symptoms are due to the patient’s underlying condition or the treatment. For example rashes may be caused by the underlying infection or occur as a result of antibiotic allergy. The problem becomes even more complicated when the patient is taking more than one drug. The history of the events surrounding the onset of the adverse reaction is often most important.
Laboratory diagnosis: There is no single test for antibiotic allergy a basic problem in diagnosing antibiotic allergy; a basic problem in diagnostic antibiotics allergy by immunological methods is the fact that most antibiotics are not complete antigens but rather haptenic metabolites of the parent drug coupled with a carrier tissue protein. With exception of penicillin immuno-reactive drug metabolites have rarely been identified.
Both skin prick and allergen specific IgE (RAST) test can be performed. RAST tests are less sensitive and give less information than skin testing to penicillin allergens. In general, RAST testing should only be used in patients who cannot be skin tested.
Skin testing for antibiotics allergy: Skin testing is of definite value in assessing hypersensitivity to certain antibiotics primarily penicillin, but is not helpful in predicting reactions caused by IgE antibiotics. Skin testing should only be performed by specialists due to risk of anaphylaxis. Most non-pruritic maculopapular rashes will not be predicted by skin testing.
Semi synthetic such as ticarcillin and piperacillin contain same nucleus as penicillin G hence sensitivity to these antibiotics can be assessed by skin testing to penicillin as well as the parent drug. Cephalosporin share a common beta-lactam ring with the penicillin but the degree of cross-reacting is quite low. Mon bactams such as aztreonam may be safely administered to penicillin allergic subjects by carbapenems such as imipenem represents as a significant risk to penicillin-allergic patients and should be withheld from penicillin skin test positive patients.