Drug Allergy

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IDIOSYNCRATIC REACTIONS
DEFINITION:
Idiosyncratic drug reactions are
“Adverse drug reactions that do not occur in most patients at any dose and do not involve the known pharmacological properties of the drug and cause remain unknown”
A genetic or acquired abnormality in a particular metabolic pathway.
Certain idiosyncratic reactions can result from genetic polymorphisms that cause individual differences in drug pharmacokinetics
Adverse reactions, such as cardiac arrhythmias caused by drugs that affect potassium channels, would not be idiosyncratic because they involve known pharmacological properties of the drug.
Example
Antipsychotic drugs such as chlorpromazine and clozapine cause infrequent reactions such as rhabdomyolysis (breakdown of striated muscle) and liver toxicity
One tablet of Chloroquine may cause vomiting and abdominal pain .

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