Allergic Drug Reactions
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| Penicillin - probably the most common cause of allergic drug reactions |
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Drug-induced illness is one of the major public health problems today. In the US, between 3-5% of medical hospital admissions are due to adverse drug effects, and 10-20% of patients hospitalized for other reasons have any adverse response to a drug prescribed while they are hospitalized. |
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In clinical studies, hospitalized patients, who generally receive more than one drug during their stay, are the people most carefully monitored for side effects. About 30% of them develop some drug reaction during their hospitalization. Most of these are not allergic reactions, but many of the more serious ones are. Other studies attribute 2.7 to 34.4% of all drug reactions to an allergic response. |
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Not all allergic drug reactions are due to the drug itself. Some may be the response of the immune system to traces of impurities or additives in a medicine or to a drug’s metabolites, the substances that result from the chemical breakdown of the drug in the body. |
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Some drugs produce a single type of reaction; while others can trigger a number of effects. For example, an allergic reaction to penicillin may manifest itself in any one of at least seven forms, including anaphylaxis, fever, and severe contact dermatitis. |
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Certain parts of the body seem to be more susceptible to allergic drug reactions, particularly the skin, lungs, liver, kidneys, blood and blood vessels. A drug allergy may affect a single organ and a localized area of the body, or it may affect many organs and many sites the same time. |
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| Many allergic drug reactions were undetected |
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| Because drugs may affect several organs in the body, it is sometimes hard to decide whether a patient’s symptoms result from the illness itself or from an allergic reaction to a drug. For example, a rash may appear during or after some streptococcal infections. Yet, a rash may also be a symptom of an allergy to penicillin, an antibiotic used to treat the same streptococcal infections. |
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| Common drugs that cause allergic reactions |
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| Penicillin is probably the most common cause of drug allergy, with some type of allergic response occurring in one of every 50 persons who take this antibiotic. About 76% of these responses are skin reactions (hives, rashes, contact dermatitis). About 22% are systemic (serum sickness, drug fever, vasculitis, angioedema, wheezing). Around 2% of the reactions to penicillin involve anaphylactic shock. |
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| Other antibiotics that may cause drug allergy include: |
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- Neomycin used in eye drops
- Streptomycin
- Chloramphenicol used in treating Rocky Mountain spotted fever, typhoid fever, and certain types of meningitis
- Aspirin, which is used to relieve pain and reduce fever, may also result in drug allergy.
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| Other common drugs that may cause allergic reactions include: |
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- Insulin used for treating diabetes
- Anti-tuberculosis medications and other antibiotics not listed above
- Anticonvulsants, barbiturates, local anesthetics
- Organ extracts, vaccines, tranquilizers and sleeping pills, laxatives
- Drugs used to treat hyperthyroidism and heart disorders.
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