The document discusses adverse drug reactions (ADRs), defined as harm caused by a medication at normal doses during normal use. It describes the types of ADRs, including type A reactions which are augmented and predictable, and type B reactions which are bizarre and unpredictable. The mechanisms of ADRs are also explained, including humoral reactions mediated by antibodies and cell-mediated reactions involving T-lymphocytes. Finally, the document outlines some ways to prevent ADRs, such as avoiding inappropriate drug use, considering a patient's history, and watching for potential drug interactions.

1. Adverse Drug Reactions
- Saiyam Agarwal
- B.Pharm
- SRMSCET,
Bareilly

2. Contents:-
• Introduction
• Adverse Drug Events
• Types of ADRs
• Important Terminology
• Mechanism of ADRs
• Prevention/Precautions
• References
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3. Introduction:-
• All drugs can produce adverse effects, there are no drugs in
the universe without a adverse effect or side effect.
• Adverse drug reactions/response is abbreviated as ADR.
• ADR is “Any injury to the body that is caused by any
medication”.
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• In other words, “ADR is any response of a drug that is
noxious, unintended and occurs at doses used for diagnosis,
prophylaxis or therapy or for the modification of physiologic
function”.
• It should be noted that there is a causal link between a drug
and an adverse drug reaction.
• In sum, an adverse drug reaction is harm directly caused by
the drug at normal doses, during normal use.
• They are more common with multiple drug therapy and in
the elderly.

5. Adverse drug events:-
• Adverse drug event is abbreviated as ADE.
• ADE is ‘any untoward medical occurrence that may present
during treatment with a medicine, but which does not
necessarily have a causal relationship with the treatment’.
• EXAMPLE……????
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6. Types Of ADRs:-
• Generally there are 5 types of ADR that are considered they are Type A,
Type B, Type C, Type D, Type E.
• Most common ones are:-
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TYPE A or AUGMENTED TYPE B or BIZARRE
• Predictable • Unpredictable
• Dose dependent(Quantitative) • Dose independent(Qualitative)
• Predicted from known pharmacology
of drugs.
• Based on peculiarities of the patient,
immunological/genetic basis.
• Include side effects, toxic effects, and
consequences of drug withdrawal.
• Include allergy and idiosyncrasy.
• Mostly preventable & reversible. • Mostly serious & requires withdrawal
of drugs, fatal.
• Example; dryness of mouth and
blurring of vision due to atropine.
• Example; hemolysis with primaquine.

7. Important terminology:-
1. Side Effects:- Unwanted, unavoidable PD effects,at therapeutic doses.
• Not so serious, can be predicted from the pharmacological profile of a drug at
a given %age of drug recipients.
• Reduction in dose, usually ameliorates the symptoms.
2. Secondary effects:- Indirect consequences of primary action of drug.
Ex. Suppression of bacterial flora by tetracycline leads to superinfections.
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3. Toxic effects:- Result from excessive pharmacological action of the drug
due to overdosage or prolonged use. Ex: Drug induced tissue damage.
Toxicity may result from extension of the therapeutic effect itself, e.g. coma
by barbiturates.
4. Poisoning:- Harmful effects of chemical on biological system. It results
from high doses(it is the dose that distinguishes a drug from poison).
5. Intolerance:- It is the appearance of characteristic toxic effects of a drug in
an individual at therapeutic doses. Ex: Chloroquine(vomiting and abdominal
pain)
6. Idiosyncrasy:- Genetically determined abnormal reactions to a chemical.
Ex: Barbiturates(excitement and mental confusion).

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7. Drug allergy:- Immunologically mediated
reaction producing symptoms which are unrelated to
pharmacodynamic profile of the drug.
8. Drug abuse:- Refers to use of a drug by self
medication in a manner and amount that deviates
from the approved medical and social patterns in a
given culture at a given time.
9. Drug addiction:- It is a pattern of compulsive
drug use characterized by overwhelming
involvement with the use of a drug.

10. How does an ADR differ from a side effect or
allergy?
• An allergy is an adverse drug reaction mediated by an
immune response (e.g., rash, hives). A side effect is an
expected and known effect of a drug that is not the intended
therapeutic outcome. The term “side effect” tends to
nominalize the concept of injury from drugs. It has been
recommended that this term should generally be avoided in
favor of adverse drug reaction.
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11. Mechanism of ADRs:-
• A. Humoral
• Type-I (anaphylactic) reactions Reaginic antibodies (IgE) are produced
which get fixed to the mast cells. On exposure to the drug, AG: AB
reaction takes place on the mast cell surface releasing mediators like
histamine, 5-HT, leukotrienes (especially LT-C4 and D4), prostaglandins,
PAF, etc. resulting in urticaria,itching, angioedema, bronchospasm, rhinitis
or anaphylactic shock. The manifestations occur quickly after challenge
and are called immediate hypersensitivity.
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Type-II (cytolytic) reactions Drug + component of a specific tissue cell
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, e.g. thrombocytopenia,
agranulocytosis, aplastic anaemia, haemolysis, organ damage (liver,
kidney, muscle).
Type-III (retarded, Arthus) reactions These are mediated by circulating
antibodies (predominantly IgG, mopping AB). AG: AB complexes bind
complement and precipitate on vascular endothelium giving rise to a
destructive inflammatory response. Manifestations are rashes, serum
sickness (fever).
B. Cell mediated
Type-IV (delayed hypersensitivity) reactions These are mediated
through production of sensitized T-lymphocytes carrying receptors for
the AG. On contact with the AG these T cells produce lymphokines
which attract granulocytes and generate an inflammatory response, e.g.
contact dermatitis, some rashes, fever, photosensitization. The reaction
generally takes > 12 hours to develop.

13. Preventions of adverse effects of drugs:-
1. Avoid all inappropriate use of drugs in the context of patient’s clinical
condition.
2. Use appropriate dose, route and frequency of drug administration based on
patient’s specific variables.
3. Elicit and take into consideration previous history of drug reactions.
4. Elicit history of allergic diseases and exercise caution (drug allergy is
more common in patients with allergic diseases).
5. Rule out possibility of drug interactions when more than one drug is
prescribed.
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14. References:-
• K.D. Tripathi, “Essential of Medical Pharmacology”, Seventh edition,
Published by Jaypee Brothers medical publishers, Page no. 82-91.
• Links:-
• https://www.youtube.com/watch?v=2tmw9x2Ot_Q
• https://www.slideshare.net/virajshinde9659/adverse-drug-reaction-
83455149
• https://www.youtube.com/watch?v=H77AW3Z-Ntc
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