Classification of ADRs

Cause based classification

1. Type A (augmented) reactions: predicted from the known pharmacology of the drug. These reactions are dose-dependent.
2. Type B (bizarre/idiosyncratic) reactions: reactions are not predicted from the known pharmacology of the drug. They appear relatively dose-independent, as very small doses might already elicit symptoms.
   
3. Type C (chemical) reactions: which are related to the chemical structure and its metabolism, e.g. paracetamol hepatotoxicity (rare since they are already noted during LI/LO phase)
   
4. Type D (delayed) reactions: which appear after many years of treatment,
   
5. Type E (end of treatment) reactions: occur after drug withdrawal
   

Severity classification

• Death
  
• Life-Threatening
  
• Hospitalization (initial or prolonged)
  
• Disability - significant, persistent, or permanent change, impairment, damage or disruption in the patient's body function/structure, physical activities or quality of life.
  
• Congenital Anomaly
  
• Requires Intervention to Prevent Permanent Impairment or Damage

Casuality assessment

• Certain : proven on dechallenge and rechallenge
• Probable : dechallenge confirms.cannot rechallenge
• Possible : can be explained by concurrent disease or other drugs
• Unlikely : not documented in literature
• Unclassified : additional data is awaited so not documented
• Unclassifiable : additional data has come but not fit into any categories