6.0 adverse drug reactions

adverse drug reactions

unwanted or harmful reactions which occur after administration of a drugs and is suspected/ known to be due to the drugs

ADRs is a response to a drug that is

• noxious,

• unintended

• and occurs at doses normally used for

  • prophylaxis,

  • diagnosis

  • or treatment

  • of disease/ modification of physiological function

ADR classified into 5 different categories

• augmented

• bizarre

• continuing, chronic

• delayed

• end of use/failure of therapy

type A reaction = augmented 

result from an exaggeration of a drug’s normal pharmacological action when given at the usual therapeutic dose + is normally dose dependent

example augmented reaction is

bleeding due to warfarin

augmenterd reactions include those not directly related to the desired pharmacological action of the drug

for example constipation due to codine

augmented reactions commonly known as

side effects

Type B bizarre reactions

reactions not expected from the known pharmacological action of the drug

bizarre reactions are less common and so may only be discovered for the first time after a drug as already been made available for general use

example: anaphyaxis with penicilin or skin rashes with antibiotics

type C continuing reaction persist for a relatively long time after the initial reaction

example: osteonecrosis of the jaw in patiens prescribed bisphosphonate drugs for long periods of time 5-10 years

type D delayed reactions

apparent some time after the use of a medicine

the timing off these may make them more difficult to detect

example@ cholestatic jaundice which cna occur up to 6 weeks after a tatient takes flucloxacilin

Type E end of use reactions associated with the withdrawal of a medicine

EXAMPLE: anxiety after withdrawal of tricyclic antidepressants used to treat IBS