An adverse drug reaction (ADR) is an unintended harmful reaction to a drug that occurs at normal doses. ADRs can be predictable (Type A) or unpredictable (Type B) reactions. Type A reactions are dose-dependent and caused by exaggerated pharmacology, while Type B reactions are unpredictable and unrelated to the drug's action. ADRs are also classified based on severity from minor to lethal. Photosensitivity reactions can be phototoxic or photoallergic, and some drugs have potential to cause mutagenicity, carcinogenicity, teratogenicity, or hypersensitivity reactions.

1. adverse drug reaction (ADR)

2. • Definitions:
• adverse drug reaction (ADR)
• As per WHO, ADR is any response to a drug
that is noxious and unintended is suspected to
be due to a drug and that occurs at normal
doses used in humans for prophylaxis,
diagnosis, or therapy of disease, or for the
modification of physiologic function.

3. • Adverse drug event (ADE)
• (WHO) defines an ADE as “any untoward
medical occurrence that may present during
treatment with a pharmaceutical product but
which does not necessarily have a causal
relationship with this treatment”

4. Classification Of ADRs
• Based on Type of reaction
• Type A (Augmented) reactions Predictable
• Type B (Bizarre) reactions Unpredictable
• Type C (Chemical/Chronic)
• Type D (Delayed)
• Type E (End of treatment)
• Type F (Unexpected Failure)

5. Predictable (Type A or Augmented)
reactions
• These reactions can be predicated from
pharmacological properties of the drug
• Caused by exaggerated pharmacologic response
• Dose dependent
• mostly preventable and reversible- Dose reduction
• Low mortality
• E.g.
• Anticoagulant- Bleeding
• B- blocker- Bradycardia
• Prazocin- postural hypotention

6. Unpredictable (Type B or Bizarre)
reaction
• Uncommon
• Not related to the pharmacologic action of the
drug
• Unpredictable
• more serious and require withdrawal of the drug
• High mortality
• Immunologic reactions: anaphylaxis to penicillin

7. Type C (Chemical/Chronic)
• Biological characteristics can be predicted
from the chemical structure of the drug
• Eg. paracetamol- Hepatoxicity

8. Type D (Delayed)
• Occurs after many year of treatment
• Can be due to accumulation.
• E.g:
• Chemotherapy- Secondary Tumors
• Antipsychotics: tardive diskinesia

9. Type E (End of treatment)
• Occurs on withdrawal especially when drug is
stopped suddenly
• Phenytoin withdrawal: Seizure

10. Classification Of ADRs
• Based on Severity of adverse drug reactions
• Minor: No therapy, antidote or prolongation of
hospitalization is required.
• Moderate: Requires change in drug therapy, specific
treatment or prolongs hospital stay by atleast 1 day.
• Severe: Potentially life-threatening, causes permanent
damage or requires intensive medical treatment.
• Lethal: Directly or indirectly contributes to death of the
patient.

11. Photosensitivity
• It is a cutaneous reaction resulting from drug
• induced sensitization of the skin to UV radiation.
• (a) Phototoxic
 Drug or its metabolite accumulates in the skin, absorbs light and undergoes a
photochemical reaction followed by a photobiological reaction
local tissue damage
 erythema, edema, blistering
 fast onset and shorter duration.
e..g. Tetracyclines
• (b) Photoallergic
Drug or its metabolite induces a cell mediated immune response which on
exposure to light of longer wave lengths produces a papular or eczematous
contact dermatitis
persist long after exposure
Drugs involved are sulfonamides, sulfonylureas, chloroquine,

12. Phototoxic Photoallergic
• Skin reaction occurs minutes
to hours after exposure to
agent and light
• (reddening and swelling)
• Reaction is limited to sun-
exposed skin
• May or may not be itchy
• itchy type reaction occurs 24-
72 hours after exposure to
agent and light
May spread to areas that have
not sun-exposed.
• itchy type reaction

13. Mutagenicity and Carcinogenicity
• Mutagenicity capacity of a drug to cause
genetic defects
• Carcinogenicity capacity of a drug to cause
cancer
• Oxidation of the drug
• production of reactive intermediates affect
genes and cause structural changes in the
chromosomes
• Gene defect

14. • Drug/Chemical
• modify DNA
• If that modified DNA sequences code for
factors that regulate cell proliferation/growth
• a tumour (cancer) may be produced

15. Teratogenicity
• capacity of a drug to cause foetal
abnormalities when administered to the
pregnant mother.
• The thalidomide disaster (1958–61) resulting
in thousands of babies born with phocomelia
(seal like limbs)

16. • The German drug company
developed and sold the drug.
• sedative or hypnotic
• nausea and morning
sickness in pregnant women
• Thalidomide became an over-
the-counter drug in West
Germany
• 5,000 and 7,000 infants were
born
with phocomelia (malformatio
n of the limbs)
• Throughout the world, about
10,000 cases were reported
• only 50% of the 10,000
survived

17. Hypersensitivity