Chapter 5 – Adverse Drug Reactions and Medication Errors
Issues related to drug safety
o adverse drug reactions (ADRs)
o medication errors
adverse drug reactions
The World Health Organization defines an ADR as any noxious unintended and
undesired effect that occurs at normal drug doses
Scope of the problem
Outpatient ADR's have increased, most were preventable
Antibiotics and anti infectives cause the most hospitalization for ADR
Definitions
side effect
o The nearly unavoidable secondary drug effect produced at therapeutic dose
common example is drowsiness from antihistamines and gastric irritation from
aspirin
o generally predictable and their intensity is dose dependent
toxicity
o the degree of detrimental physiologic effects caused by excessive drug dosing
o examples respiratory depression from an overdose of morphine or severe
hypoglycemia from an overdose of insulin
o toxicity has come to mean any severe ADR regardless of the dose that caused
it
Allergic reaction
o this is an immune response
o for this to occur there must be prior sensitization of the immune system; once
this has happened re exposure to that drug can trigger an allergic response
o about 10% of ADR's are due to allergy
o the intensity of the reaction is determined by the degree of sensitization of
the immune system not by the drug dose; meaning the intensity of allergic
reactions is largely independent of dose
o patient sensitivity can change over time so a drug that elicits a mild reaction
once can produce an intense reaction later
o most serious reactions are caused by penicillins
o Other common allergic reactions are from NSAIDs and sulfonamides which
includes some diuretics antibiotics and oral hypoglycemic agents
Idiosyncratic effect
an uncommon drug response resulting from a genetic predisposition
an example it is an effect that occurs in people with glucose-6-phosphate
dehydrogenase deficiency (G6PD). This is an X linked inherited condition occurring
mostly in people with African or Mediterranean ancestry. When these people take
drugs such as sulfonamides or aspirin they develop red blood cell hemolysis which
can be life threatening
paradoxical effect
Issues related to drug safety
o adverse drug reactions (ADRs)
o medication errors
adverse drug reactions
The World Health Organization defines an ADR as any noxious unintended and
undesired effect that occurs at normal drug doses
Scope of the problem
Outpatient ADR's have increased, most were preventable
Antibiotics and anti infectives cause the most hospitalization for ADR
Definitions
side effect
o The nearly unavoidable secondary drug effect produced at therapeutic dose
common example is drowsiness from antihistamines and gastric irritation from
aspirin
o generally predictable and their intensity is dose dependent
toxicity
o the degree of detrimental physiologic effects caused by excessive drug dosing
o examples respiratory depression from an overdose of morphine or severe
hypoglycemia from an overdose of insulin
o toxicity has come to mean any severe ADR regardless of the dose that caused
it
Allergic reaction
o this is an immune response
o for this to occur there must be prior sensitization of the immune system; once
this has happened re exposure to that drug can trigger an allergic response
o about 10% of ADR's are due to allergy
o the intensity of the reaction is determined by the degree of sensitization of
the immune system not by the drug dose; meaning the intensity of allergic
reactions is largely independent of dose
o patient sensitivity can change over time so a drug that elicits a mild reaction
once can produce an intense reaction later
o most serious reactions are caused by penicillins
o Other common allergic reactions are from NSAIDs and sulfonamides which
includes some diuretics antibiotics and oral hypoglycemic agents
Idiosyncratic effect
an uncommon drug response resulting from a genetic predisposition
an example it is an effect that occurs in people with glucose-6-phosphate
dehydrogenase deficiency (G6PD). This is an X linked inherited condition occurring
mostly in people with African or Mediterranean ancestry. When these people take
drugs such as sulfonamides or aspirin they develop red blood cell hemolysis which
can be life threatening
paradoxical effect
