ADVERSE DRUG REACTIONS
Download
Report
Transcript ADVERSE DRUG REACTIONS
DR. SHABANA ALI
Adverse Drug Reactions
(ADR)
Harm associated with the use of a given
medications
OR
Unwanted or harmful reaction experienced
after the administration of a drug or
combination of drugs under normal
conditions of use
ADR= significant morbidity & mortality
Range
from
mild
reactions
(drowsiness, nausea, itching& rash);
disappear after discontinuation of drug
OR
Severe
reactions
(respiratory
depression, neutorpenia, hepatocellualr
injury, hemorrhage, anaphylaxis
ADR most common in
Women
Elderly (>60 y old)
Very young (1-4 y)
Patients taking more than one drug
Classification of ADR
Rawlin & Thompson classification
Traditional classification
A&B
About 80% of ADR----Type A reactions
ABCD
1) Type A Reactions
a) Related to pharmacological action of drug
Extensions of the principal pharmacological action
of the drug
Cont.
b) Predictable
Relatively easily predicted by preclinical and clinical
pharmacological studies
c) Common
Type A reactions not serious---common
d) Dose-dependent
Usually dose dependent
Type A reactions
(classes)
i) Toxicity of overdose (Drug overdose)
An adverse drug reaction caused by excessive dosing
e.g., hepatic failure with dose of paracetamol
Headache with antihypertensives
hypoglycemia with sulfonylurea;
ii) Side Effects
Nearly unavoidable secondary drug effect produced
by therapeutic doses
intensity is dose dependent
Occur immediately after initially taking drug or may
not appear until weeks after initiation of drug use
E.g., sedation with antihistamines
iii) Secondary Effects
Secondary pharmacological effect
E.g., development of diarrhea with antibiotic therapy
due to altered GIT bacterial flora
Orthostatic hypotension with a phenothiazine
iv) Drug Interactions
When two drugs taken together & they effect each
other’s response pharmacologically or kinetically
E.g., one drug slow metabolism of 2nd drug
blood
conc.= toxicity
Theophylline toxicity in presence of erythromycin
2) Type B Reactions
Unrelated
to known pharmacological
actions of drug
Unpredictable
Often caused by immunological &
pharmacogenetic mechanisms
Unrelated to dosage
Comparatively rare & cause serious illness
or death
cont.
Results
(more
likely)
in withdrawal of
marketing authorization
Often not discovered until after drug is
marketed
Both environmental & genetic factors =
important in this reaction
Type B Reactions (classes)
i) Drug Intolerance
Lower threshold to normal pharmacological action of a
drug
e.g., tinnitus (single average dose of aspirin)
ii) Hypersensitivity (immunological reaction)
Immune mediated response to a drug agent in
sensitized patient
e.g., anaphylaxis with penicillin
iii) Pseudoallergic Reaction
Direct mast cell activation & degranulation by
drugs (opiates, vancomycin & radiocontrast media)
Clinically
indistinguishable
hypersensitivity
but
immunologic reactions)
not
form
involve
Type
IgE
I
(non
iv) Idiosyncratic Reactions
An uncommon & abnormal response to drug
Usually due to genetic abnormality
Affect drug metabolism & receptor sensitivity
Harmful even fatal, appear in low doses
E.g., Anemia (hemolysis) by antioxidant drugs
(G6PD deficiency)
Paralysis due to succinylcholine (enzyme
deficiency)
3) Type C (chronic)
Reactions
Associated with long-term drug therapy
Well known and can be anticipated
Adaptation occurs = discontinuation of
drug=abstinence syndrome
E.g. opoids, alcohol, barbiturates
4) Type D (delayed) Reactions
Carcinogenic & teratogenic effects
Delayed in onset
Very rare
Carcinogenic Effect
Medication lead to cancer; take >20 y to develop
Teratogenic Effect
Drug- induced birth defects
Sign & Symptoms of ADR
Mild, moderate, severe or lethal
Sign & symptoms manifest soon after 1st dose or
only after chronic use
e.g., Allergic reactions occur soon after drug is taken
usually 2nd time ( itching, rash, eruption, upper or
lower airway edema with dyspnea & hypotension)
Idiosyncratic reactions=any unpredicted symptom
Mechanisms of ADR
Type A =non immunological, reversible with reduction
of dose, non serious, extension of pharmacological
effects
Type B
Biochemical
mechanism
unrelated
to
pharmacological
Immunologic = Hypersensitivity (Type I, II, III, IV)
OR
Non immunologic (direct)=
Pseudoallergic,
idiosyncratic, intolerance
Mechanism of Type B
Reactions
i) Often mediated by a chemically reactive
metabolite
Non detoxification of metabolite
Direct cytotoxicity
Direct tissue damage + necrosis
ii) Bind to NA
altered gene product
Bind to a larger macromolecule
inducing
immune response (produce Ab & bind to Ab)
Drug Hypersensitivity
(allergic) Reaction
Common form of adverse response to drugs
Classification (Gell & Coombs)
Type I reactions (IgE-mediated)
Type II reactions (cytotoxic)
Type III reactions (immune complex)
Type IV (delayed, cell mediated)