ADVERSE DRUG REACTIONS:
A response to a drug which is noxious &
Unintended & which occurs at normal doses used
in man.
ADVERSE DRUG EVENTS:
Any untoward medical occurance that may present
during treatment with a pharmaceutical
product(drug),but which does not necessarily have
a causal relationship with this treatment.

⦁ WHO defined it as the “science & activities related
to the detection, assessment, understanding &
prevention of adverse effects or any other drug
related problems.”
⦁ The information generated by pharmacovigilance is
useful in educating doctors about ADRs & in the
official regulation of drug use.
⦁ It has important role in rational use of medicines &
assessing safety of medicines.

ADRs can be minimised but not eliminated by
observing the following practices:
 Avoid all inappropriate use of drugs in the context
of patient’s clinical condition.
 Use correct dose,route & frequency of drug
administration based on patient’s specific
variables.
 Take into consideration about previous history of
drug reactions,allergic diseases &exercise
caution(drug allergy is more common in allergic
patients)

 Rule out possibility of drug interactions when
more than one drug is prescribed.
 Adopt correct drug administration technique
(eg:iv inj of vancomycin must be slow).
 Carry out appropriate laboratory monitoring
(serum drug levels with lithium).
SEVERITY OF ADVERSE DRUG REACTIONS:
Minor:No therapy,antidode or prolongation of
hospitalization is required.
Moderate:Requires change in drug therapy,specific
treatment or prolongs hospital stay atleast one
day.
Severe:Potentially life threatening,causes
permanent damage/requires intensive medical
treatment.
Lethal:Directly/indirectly contributes to death of
the patient.

Adverse drug effects may be categorized into:
1).Side effects:
Unwanted & unavoidable p’dynamic effects occurs at
therapeutic doses.
 Reduction of dose generally ameliorates the symptoms.
 Side effects may be based on same action as the therapeutic
effect.
eg; Atropine is used as preanaesthetic for its antisecretory
action,the same action produces dryness of mouth as side
effect.
 Many drugs have been developed from observation of side
effects.
eg; sulfonamides (antibacterial) used as hypoglycemic
sulfonylureas.

⦁ These are indirect consequences of a primary
action of drug.
Eg;corticosteroids weekens host defence
mechanisms so that latent TB gets activated.
3).Toxic effects:
⦁ Due to excessive p’cological action of the drug
due to overdose & prolonged use.
⦁ The effects are predictable & dose related.
⦁ They result from functional alteration(high dose of
ATROPINE causes DELIRIUM)or drug induced tissue
damage(Hepatic necrosis from PARACETAMOL
overdose).

Poisoning:
⦁ Due to large doses of drugs.
⦁ Poison endangers life by severely affecting one or more vital
functions.
MEASURES:
 Resuscitation & maintenance of vital functions: Adequate
ventilation,artificial respiration, maintenance of BP, heart
beat, body temperature & blood sugar level.
 Termination of exposure:
Removing patient to fresh air,washing skin & eyes,induction of
emesis with syrup ipecac/gastric lavage [avoided in kerosine &
CNS poisoning]

 Prevention of absorption of ingested poisons:
 20-40g(1g/kg) of activated charcoal suspension
should be administered in 200ml of water.
Strong acids& alkalies,metallic salts,iodine,
cyanides,alcohol,organic solvents are not adsorbed by
charcoal.
 Hastening elimination:
Quick removal of poison from the body by
haemodialysis,inducing diuresis/altering urinary
pH.

4).Intolerance:
known as inability to withstand/consume the drug.
Eg; only few doses of carbamazepine may cause ataxia in
some people.
5).Idiosyncrasy:
It is genitically determined abnormal reactivity to a chemical.
Peculiar to an individual because the drug reacts with the
specific gene which is specific to an individual.
Eg; Barbiturates causes excitement & mental
confusion in some individuals.

6).Drug allergy:
⦁ A medical condition that makes a individual to feel ill
when a drug is taken.
⦁ Allergic reactions occur only in a small proportion of the
population exposed to the drug & cannot be produced in other
individuals.
⦁ Occur even with smaller doses & have a different time
course of onset & duration,also called as
HYPERSENSITIVITY but not supersensitivity.
⦁ The drug/its metabolites acts as AG/HAPTEN & induce
production of AB/sensitized lymphocytes.
⦁ They are of two types: HUMORAL & CELLMEDIATED.

A. HUMORAL:
 TYPE-I(anaphylactic)REACTIONS:
On exposure to the drug,AG:AB reaction takes place on the
mast cell surface releasing mediators like
histamine,5HT,leukotrienes Prostaglandins etc.,resulting in
itching, angioedema, bronchospasm, rhinitis.
 TYPE-II(cytolytic)REACTIONS:
Drug+component of a specific tissue cells act as AG.The
resulting antibodies(IgG,IgM)bind to the target cells on
reexposure AG:AB reaction takes place on the surface of these
cells,complement is activated and cytolysis occurs.

 TYPE-III(retarded)REACTIONS:
AG:AB complexes bind complement & precipitate on
vascular endothelium giving rise to a destructive inflammatory
response.
Manifestations are rashes, serum sickness, mental symptoms,
myocarditis, nephritis(usually in 1-2weeks)
B.CELL MEDIATED:
 TYPE-IV(delayed hypersensitivity)REACTIONS:
These are mediated through production of sensitized T-
lymphocytes carrying receptors for the AG.They form
inflammatory response.
Eg:dermatitis,rashes,fever,photosensitization
takes>12hrs to develop.

TREATMENT:
 Administration of oxygen.
 0.5mg adrenaline i.m injection.
 Administer a H1 antihistaminic i.m/slow i.v.
 I.V of glucocorticoids should be added in many
cases.
 Adrenaline followed by a short course of
glucocorticoids is indicated for bronchospasm
attending drug hypersensitivity.
 Glucocorticoids are the only drug in type II,III,IV
reactions.

7).Photosensitivity:
It is a cutaneous reaction resulting from drug
induced sensitization of the skin to Uvrays.the
reactions are of two types:
a) Phototoxic:
Drugs/its metabolites accumulates in the
skin,absorbs light & undergoes a photochemical
reaction followed by a photobiological reaction
resulting in local tissue
damage.[edema,blistering etc drugs involved are
tetracyclines,thiazides]
b) Photoallergic:
Rarely AB mediate photoallergy & the
reaction takes form of flare&wheal on exposure
to sun drugs involved are
sulfonamides,chloroquines etc.

8).Drug dependence:
It is a state in which use of drugs for personal
satisfaction is accorded a higher priority than
other basic needs,often in the face of known risks
to health.
a].Psychological dependance:individual believes
optimal state of wellbeing is achieved only
through the actions of the
drugs[cocaine,opioids,BZPs].
b].Physical dependance:an altered physiological
state produced by repeated administration of a
drug which necessitates the continued presence
of the drug to maintain physiological equilibrium.
 Discontinuation of the drug leads to withdrawl
syndrome.[BZDs,alcohol,cocaine].

c].Drug abuse:social disapproval of the manner
& purpose of drug use.
d].Drug addiction:strong physiological &
psycological dependence on a drug.
Eg;Narcotics,cocaine,Amphetamines.
e].Drug habituation:a psychological dependence
on drug due to repeated consumption with a
desire to continue its use,withdrawal produces
only mild discomfort.
Eg:coffee,tea,social drinking.

9).Drug withdrawal reactions:
These reactions are produced when there
is sudden cessation of the drug or
interruption of therapy with certain other
drugs.
Eg;precipitation of MI may result from stoppage
of beta blockers.
10).Teratogenicity:
It refers to capacity of a drug to cause
foetal abnormalities when administered to the
pregnant mother.
Eg; Warfarindepressed nose,growth
retardation.

11).Mutagenicity & Carcinogenicity:
The capacity of a drug to cause genitic defects
&cancer respectively.
Usually oxidation of the drug results in the
production of reactive intermediates which effects
genes & may cause structural changes in the
chromosomes.
Eg; anticancer drugs, tobacco, estrogens, radioisotopes.
12).Drug induced diseases:
These are iatrogenic(physician induced)diseases
& functional distrubances(disease)caused by drugs
which persists even after the offending drug has
been withdrawn & largely eliminated.
eg:peptic ulcer by salicylates & corticosteroids.

References
 www.authorstream.com
 http://www.google.co.in/images
 Essentials of Medical pharmacology by K.D Tripathi
pg;no :78-86