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Adverse Drug Reaction

Adverse Drug Reaction. Unnikrishnan M K Additional Prof in Pharmacology, Manipal College of Pharmaceutical Sciences, Manipal 576 104. Introduction. Defn: Undesirable effect at normal dose: trivial OR serious Or fatal Requires Treatment  in dosing Discontinuation

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Adverse Drug Reaction

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  1. Adverse Drug Reaction Unnikrishnan M K Additional Prof in Pharmacology, Manipal College of Pharmaceutical Sciences, Manipal 576 104

  2. Introduction • Defn: Undesirable effect at normal dose: • trivial OR serious Or fatal • Requires • Treatment •  in dosing • Discontinuation • Caution in future • Occurrence • immediately or after prolonged use • or after termination • Mild ADRs common, [incidence 10-25%] •  with polypharmacy • Acceptability: linked to Therap. Use; Risk Benefit Ratio

  3. Type A: Predictable & Type B Unpredictable • Type A: Response qualitatively normal but quantitatively abnormal • Common, less serious, dose related, • corrected by dose adjustment • include side effect, toxic effect, withdrawal • Type B: Because of patient peculiarities; Eg. Allergy, idiosyncrasy • Dose related; uncommon; Serious  withdrawal of drug required • Not always predictable / preventable

  4. Severity of ADR: Minor/ moderate/ severe/ lethal • Minor: no need of therapy, antidote, or hospitalization • Moderate: requires drug change , specific treatment, hospitalization • Severe: Potentially life threatening; permanent damage, and prolonged hospitalisation. • Lethal: Directly or indirectly leads to death

  5. Prevention of ADR: [cannot be totally avoided; only minimized] [1] Avoid inappropriate drugs in the context of clinical condition [2] Use right dose, route, frequency based on patient variables [3] Elicit medication history; consider untoward incidents [4] Elicit history of allergies [in patients with allergic diseases] [5] Rule out drug interactions [6] Adopt right technique: Eg slow iv injection of aminophylline [7] Carry out appropriate monitoring [Eg PT with warfarin; Li levels]

  6. Types of ADRs viz Side effect; Secondary effect; Toxic effect [1] Side Effects: unavoidable, predictable, dose  amelioration • Occurs as Extension of the same therapeutic effect: Eg. • Atropine as antisecretory in preanesthetic medication  dry mouth • Occurs as a distinctly different effect: Eg. • Promethazine as antiallergic  sedation • Estrogen as antiovulatory  nausea • Side effect exploited for a therapeutic use: Eg • Codeine [antitussive] constipating action used in diarrhoea • Sulfonylureas [tested as antibacterials] were found tobl glucose

  7. Secondary Effects & Toxic Effects • [2] Secondary effects: Indirect effect of therapy • Eg. Iintestinal microflora killed by tetracycline superinfection • Corticosteroids  immunity  activation of latent tuberculosis • [3] Toxic effects: [Overdose or prolonged use] • Atropine  delirium ; • Paracetamol  hepatic necrosis • Barbiturates  coma; • Morphine  respiratory failure

  8. Intolerance and Idiosyncrasy • [4] Intolerance: • Opposite of tolerance: sensitivity to low doses • few doses of carbamazepine  ataxia [ defective movement/gait] • single dose of triflupromazine  muscular dystonia • [5] Idiosyncrasy: genetically determined atypical / bizarre effect • Barbiturate  excitement & mental confusion • Quinine  cramps , diarrhoea, purpura, asthma, vascular collapse

  9. Drug allergy: [ or hypersensitivity] • [6] Drug allergy: [ or hypersensitivity] • Immunologically mediated • Independent of dose • Occurs in a small proportion; • Prior sensitization required • 1-2 weeks required after first dose • Drug acts as an antigen or Hapten • Chemically related drugs may show cross sensitivity • Same drug can cause diff allergic reactions in diff individuals

  10. Drug allergy: continued.. • Variable time course: Sensitive people may later tolerate drug • Type I: urticaria, angioedema, asthma, anaphylactic shock • Type II: Thrombocytopenia, agranulocytosis, aplastic anemia, SLE • Type III: Arthralgia, lymphadenopathy, Steven Johnson Synd. • Type IV: contact dermatitis, fever, photosensitisation Eg: penicillin, sulfonamides, carbamazepine, methyldopa

  11. [7]Photosensitivity: [phototoxic & photoallergic] • Phototoxic: Drug accumulates in skin  absorbs light  photochemical reaction  photobiological reaction  tissue damage [Eg erythema, edema, blistering etc] Eg tetracyclines • Photoallergic: drug  cell mediated immune response  contact dermatitis on exposure to light. Eg sulfonamides, griseofulvin etc.

  12. ADRs continued.. • [8]Drug Dependence: Psychological: (Habituation) & Physical dependence: with withdrawal symptoms • [9]Teratogenicity: Drug use in pregnancy affects offspring Eg Thalidomide  phocomelia; phenytoin  cleft palate • [10 ]Carcinogenicity & mutagenicity: Anticancer drugs, estrogens • [11] Drug induced deseases, Iatrogenic diseases : Salicylates  peptic ulcer; Phenothiazines  parkinsonism; INH  hepatitis

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