This document defines adverse drug reactions (ADRs) and describes how they are classified and factors that can predispose patients to them. It defines ADRs as any noxious, unintended response to a drug given at normal doses. ADRs are classified into types A-F based on factors like when they occur or their relationship to the drug's normal pharmacology. Common predisposing factors include patient characteristics, drug interactions, and multiple drug use. The document outlines steps for monitoring, preventing, and managing ADRs.

1. ADVERSE DRUG REACTIONS
Prepared by:
KRISHNA PRASAD DAHAL
PHARM D. (PU)
RPh. (Pb); RPh. (NEPAL)
CLINICAL PHARMACIST at G.N.S. SAGARMATHA ZONAL HOSPITAL
FACULTY MEMBER OF PHARMACOLOGY AND TOXICOLOGY
SAPTARISHI HEALTH SCIENCE COLLEGE
RAJBIRAJ, NEPAL

2. ADVERSE DRUG REACTIONS
WHO Defines ADRs as, “ any response to a drug which is noxious and unintended
and which occurs at dose normally used in man for prophylaxis, diagnosis and
treatment of disease.”
ADRs also can be defined as any unfavorable or unintended sign including the
abnormal laboratory findings, symptoms or diseases temporarily associated with
the use of any medicinal product
Adverse events are any untoward medical occurrence that at any dose
• Results in death
• Result in permanent morbidity
• Result in disability
• Require the patient hospitalization
Many ADRs may be preventable through rational prescribing and careful
monitoring of drug therapy.

3. Classification of ADRs
Classification of ADRs are useful for recognizing and avoidance or
management of ADRs and can be done in following ways
• Type A: Augmented
• Type B: Bizarre
• Type C: Continuous/Chronic
• Type D: Delayed
• Type E: End of therapy
• Type F: failure of therapy
A) Type A: Augmented
• These reactions are normal but quantitatively exaggerated pharmacological effect of
the drug.
• These are very common reactions and accounts 80% of the reaction.
• They include pharmacological effect of the drug as well as secondary
pharmacological effect of drug.

4. B) Type B: Bizarre effect
• They are quantitatively abnormal effect which appears unrelated to the drugs
normal pharmacology.
• They are most serious in nature more likely to cause often abnormal
morbidity as well as mortality.
• There cause can be either genetic abnormality or hypersensitivity reactions.
• Genetic abnormality accounts deficiency of enzymes or due to abnormal
receptor activity an happens in very small population and can be seriously
dangerous.
• Hypersensitivity can be due to antigen antibody reactions where 1st dose act
as an antigen and antibodies are produced against them subsequent
administration can cause antigen-antibody reactions.
• E.g. penicillin allergy

5. C) Type C: chronic or continuous
• This reaction happens due to chronic use of the drugs.
• It involves dose accumulation in the central and tissue compartment of the
body.
• E.g. Liver cirrhosis with continuous use of Paracetamol.
• Ulcer due to chronic use of NSAIDs.
D) Type D: Delayed effect
These reactions are found long term after use of the drug is stopped.
E.g. Teratogenesis: Birth defect that is evident after but cause was
drug taken during 1st trimester of pregnancy.
Carcinogenesis: Carcinoma detected after long term use of drug

6. E) Type E: End of therapy
ADRs are manifested after withdrawal of the drug which was
used for long period.
These type of reactions are uncommon.
e.g. sudden abrupt withdrawal of β-blockers will cause reflex
tachycardia by un-regulation of β receptors and can cause
Ischemic Heart Disease.
F) Type F: Failure of therapy
This type of ADR is manifested by not taking the drug in right
time.
It is also often caused by Drug Interaction and also from
concomitant disease condition.

7. E.g. Concomitant disease condition
• A patient suffering from Ischemic Heart Disease (IHD) used to have frequent attacks of angina
and he has to keep its emergency drug nitrates.
• If a patient is concomitantly suffering from Alzheimer’s disease which has symptoms of
Amnesia
• If the patient has got heart attack, the patient forgot that where he has kept his medicine.
• This leads in converting simple angina into myocardial infarction (MI) due to lack of supply of
medicine in time and leads to death of patient.
PREDISPOSING FACTORS OF ADRs
Predisposing factors that result in ADRs can be;
a) Patient factor
i) age
ii) gender
iii) genes
iv) concomitant disease

8. b) Drug interaction
c) Multiple drug use
d) Prescription error
e)Alcohol intake/ smoking/ pollution
ADVERSE DRUG REACTIONS MONITORING
Steps involved in monitoring of ADRs are:
• Identifying ADRs
• Assessing causality (relationship between drug and suspected reactions)
• Documentation of ADRs.
• Symptomatic treatment of ADRs.
• Reporting ADR to ADR regulating Authorities/ pharmacovigilance center.

9. Prevention of ADRs
• Not prescribing the drug unless absolutely indicated.
• Checking previous ADR history.
• Increasing rational prescribing of drugs.
• Dose adjustment in patients with concomitant renal and hepatic diseases.
• Incase of pregnant and breast feeding woman, prescribe alternative
medication if available that reduce ADRs or else monitor closely during
medication period.
• Warning the patient about common side effects and potential ADRs of the
given medicine.

10. Management of ADRs
• Discontinue drug if:
a) can be safely stopped
b) adverse events is life threatening
c) there is reasonable alternative
• Modification of dose or reduce precipitating factor.
• Provide supportive and palliative care.
• Proper rehabilitation of patients.

11. THANK YOU