Adverse Drug Reactions

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Types of Adverse Drug Reactions: 

Types of Adverse Drug Reactions Dr. R. K. Dixit. Professor Pharmacology and Therapeutics K. G. M. U. Lucknow …....“There are no safe drugs, there are only safe doctors” B Berde ..


Discuss epidemiology Define adverse drug reactions Different Classes of ADRs Describe basic methods to Detect Document ADRs Objectives……

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All Drugs are Dangerous No Drug is Dangerous if used properly All possible ADRs can not be known before marketing (....Need for Pharmacovigilance) Some drugs are dangerous Some drugs have a low therapeutic ratio Some drugs have a low incidence of ADRs Some ADRs can be predicted (Type A) Some ADRS occur after stopping BAD GOOD Some ADRs can not be predicted (Type B) Some ADRs just after starting treatment How dangerous a drug is, depends on the skill of the prescriber ( and..luck of PPP) Some ADRs appear only after overdosing Some ADRs (S/E) appear in normal dose Some ADRS occur after long-term Tt Dangerous drugs may have great therapeutic potential Some ADRS occur during short-term Tt

Epidemiology of ADRs (Key Point)…: 

Substantial morbidity and mortality Incidence varies with study methods, population, and ADR definition 4th to 6th leading cause of death among hospitalized patients 6.7% incidence of serious ADRs 0.3% to 7% of all hospital admissions 30% of medical inpatients develop an ADR 5% of patients are allergic to > 1 drugs * JAMA. 2007;379:1500-1505. Epidemiology of ADRs (Key Point)…

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ADRs leads billion dollars (Rs……?) in health care expenditures and double the basic cost of treatment. Fewer than one-tenth of ADRs are ever reported Prescribers recognize or attribute ADRs less than one-fourth of the time when they occur Up to 70-80% of adverse drug reactions (ADRs) are preventable by attention to patient and cooperation among P rescribers P harmacists P aramedical P atients P atient attendants P olicy makers


WHO Response to a drug that is noxious and unintended and that occurs at doses used in humans for prophylaxis, diagnosis, or therapy of disease, or for the modification of physiologic function Excludes therapeutic failures, overdose, drug abuse, noncompliance, and medication errors Generally the causality of adverse drug reactions is uncertain, making it more accurate to refer to ‘Suspected ADRs’. Definition………

ADRs by Drug Class: 

7 ADRs by Drug Class Adapted From: 12/12/2012

Body Systems Commonly Involved: 

Hematologic CNS Dermatologic Hepatobiliary Cardiovascular Gastrointestinal Genitourinary Respiratory Body Systems Commonly Involved


Frequency Onset Severity Type Classification Frequency The World Health Organization standardization of frequency. Very common (>1/10 patients) Common (>1/100) Uncommon (>1/1000) Rare (>1/10,000) Very rare (<1/100,000)


Onset of event: Acute within 60 minutes Sub-acute 1 to 24 hours Latent 1- 2 days Late > 2 days Classification

Classification - Severity: 

Severity of reaction: Mild bothersome but requires no change in therapy Moderate requires change in therapy additional treatment hospitalization Severe disabling or life-threatening, teratogenic (Serious) Classification - Severity

Classification - Severity: 

Serious ADR Result in death Life-threatening Cause disability Require hospitalization Prolong hospitalization Cause congenital anomalies Require intervention to prevent permanent injury Classification - Severity

PowerPoint Presentation: 

Classification of ADRs Adopted from- Rawlin and Thompson 1991

Classification (A,B,C,D,E,F……..): 

Type A ( Augmented Pharmacological Effect) Extension of pharmacologic effect Often predictable and dose dependent Responsible for at least two-thirds of ADRs e.g., bradycardia by propranolol Classification (A,B,C,D,E,F……..)


Type B (Bizarre…..Unexpected) Idiosyncratic (Genetically determined) Allergies (Immunologically determined) Unpredictable Rare e.g., Chloramphenicol and Aplastic anemia Classification

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Type “A” reactions Predictable, common and related to Pharmacological action of the drug Usually dose dependent High morbidity Low mortality Responds to dose reduction Toxicity of overdose (Hepatotoxicity with paracetamol) Side effects (e.g. Sedation with antihistamines) Secondary effects (e.g.Diarrhea with antibiotic therapy) Drug interaction (e.g. OCPs and Rifampicin) Unpredictable, rare, related / not to the pharmacological actions Rarely dose dependent Low morbidity High mortality Responds to drug withdrawal Intolerance (e.g. carbamazepine and ataxia) Hypersensitivity i.e. Immunological reaction (e.g. Anaphylaxis ) Idiosyncratic reaction. ( Genetically determined. e.g. haemolysis with primaquine in the persons of G-6-PD deficiency). Type B reactions


Type C ( Chronic effects) Associated with long-term use Involves dose accumulation e.g., phenacetin and interstitial nephritis or antimalarials and ocular toxicity Classification


Type D (Delayed Effect) Remote effects Carcinogenicity (e.g., immunosuppressants) Mutagenicity Teratogenicity (e.g., foetal hydantoin syndrome) Classification

Teratogenic Effects: 

12/12/2012 19 Teratogenic Effects


Type E (End of treatment Effect) Adverse Effects which occur when the drug is stopped Stopped Suddenly Hydrocortisone may precipitate HPA suppression Beta blockers may aggravate angina Anticonvulsants may precipitate seizures Classification

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Type F: ( Failure of Treatment) Unexpected failure of therapy. (May be caused by drug interactions.) eg . failure of oral contraceptives by Rifampicin .

ADR Risk Factors: 

A ge (children and elderly) S pecial population group ( Pregnant, Lactation) M ultiple co-morbid conditions E nd-organ dysfunction and Altered physiology I nappropriate medication prescribing, use, I nappropriate monitoring P rior history of ADRs E xtent (dose) and duration of exposure G enetic predisposition M ultiple medications ADR Risk Factors

ADR Frequency by Drug Use: 

ADR Frequency by Drug Use 0-5 6-10 11-15 16-20 Number of Medications Frequency (%) May FE. Clin Pharmacol Ther 2009;55:1322-8

ADR Detection: 

Subjective report Patient complaint Objective report: Direct observation of event Abnormal findings Physical examination Laboratory test Diagnostic findings ADR Detection

Preliminary Assessment (Who, what, when, where, how? ): 

What has happened? Who is involved? When did the event take place? What is the most likely cause? Is this an exacerbation of a pre-existing condition? Alternative explanations / differential diagnosis Where did the event occur? How has the event been managed thus far? Preliminary Assessment (Who, what, when, where, how? )

Diagnosing Adverse Drug Reaction : 

12/12/2012 26 Diagnosing Adverse Drug Reaction Step 1 Identify the drug(s) taken by the patient Step 2 Verify that the onset of signs and symptoms was after the initiation of pharmacological intervention Step 3 Determine the time interval between the initiation of drug therapy and the onset of the adverse drug event

Diagnosing Adverse Drug Reaction : 

12/12/2012 27 Diagnosing Adverse Drug Reaction Step 4 Stop drug therapy and monitor the patient’s status Step 5 If appropriate, restart drug therapy and monitor for recurrence of adverse drug event Step 6 Think positively about the possibility of ADR Report to the Pharmacovigilance Cell

Reporting adverse drug events : 

12/12/2012 28 Reporting adverse drug events An event is serious and should be reported when the patient outcome is Death Life-threatening Hospitalization Disability Congenital anomaly Requires intervention to prevent permanent impairment or damage

Detailed Description of Event PQRSTA Acronym: 

Detailed Description of Event PQRSTA Acronym P Q R S T A

Detailed Description of Event: 

History of present illness Evaluate: PQRSTA P rovoking and P alliative factors Q uality (character or intensity) R esponse to treatment, R eports in literature S everity / extent, S ite (location) T emporal relationship (onset, duration, frequency) A ssociated signs and symptoms A lternate possibilities Detailed Description of Event

ADR Information Resources: 

Reference books Medical and pharmacotherapy textbooks Pharmacopoeias Package inserts, PDR, MIMS, CIMS, AHFS, USPDI Specialized ADR resources Meyler’s Side Effects of Drugs Textbook of Adverse Drug Reactions ADR Information Resources

ADR Information Resources: 

MEDLARS databases (e.g., Medline, Toxline, Cancerline, Toxnet) Excerpta Medica’s Embase International Pharmaceutical Abstracts Biological Abstracts (Biosis) Science Citation Index Clin-Alert and Reactions ADR Information Resources

PowerPoint Presentation: 

12/12/2012 33 Preventing adverse drug events Rational approach A ccurate diagnosis B enefits versus risks of drug therapy C ritical assessment of the need for pharmacotherapy D ecide Individualization of drug therapy E ducate the patients regarding disease and treatment F urther reassessment of therapy

The “Rights”: 

The “Rights” Comply rights to be free of wrongs: R ight drug R ight patient ( Age, Sex, Race, Genetics, Economical condition) R ight disease R ight dosage form R ight dose R ight route R ight time R ight place R ight environment R ight diet R ight emotion R ight cost (overall financial burden) R ight other co-prescribed treatment, therapy (……..OTC) R ight duration R ight withdrawal R ight registration

Take Home Messages….. : 

12/12/2012 35 Take Home Messages….. ADRs – responsible for significant mortality and morbidity ADRs- Types A and B (A,B,C,D,E,F……) About 80% of all adverse drug reactions are type A. ADRs are preventable to the extent of 70- to 80%. Remember Rights………. Timely reporting of ADRs A voids mortality D ecrease the cost of health care R educes morbidity