Predictable reactions are usually dose dependent, are related to the known pharmacologic actions of the drug, and occur in otherwise healthy individuals, They are estimated to comprise approximately 80% of all ADRs. Unpredictable are generally dose independent, are unrelated to the pharmacologic actions of the drug, and occur only in susceptible individuals.
Unpredictable reactions are subdivided into drug intolerance, drug idiosyncrasy, drug allergy, and pseudoallergic reactions.
Both type A and B reactions may be influenced by genetic predisposition of the patient
DOI - Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology (DOI)