Friday, December 28, 2012

Classification of Adverse Drug Reactions

There are several ways of classifying ADRs. The simplest one is that proposed by Rawlins and Thompson which was later modified by Wills and Brown.
I. Rawlins and Thompson classification: In this classification, the ADRs are categorized into two classes viz type A and type B reactions.

1. Type A reactions: These include the reactions that are predictable from the drug’s known pharmacology and are usually dose dependent. Their incidence and morbidity are generally high while mortality is usually, but not invariably low. Examples are bradycardia with b adrenoceptor blockers, hemorrhage with anticoagulants, hypoglycaemia with sulphonylureas, etc. Some type A reactions have a long latency, like teratogenicity, chloroquine retinopathy, delayed effects like vaginal adenocarcinoma in daughters of women who received diethylstilbestrol during pregnancy, etc.

2. Type B reactions: These are aberrant or bizarre effects that cannot be predicted on the basis of the drug’s pharmacology. These reactions are generally unrelated to dosage and though comparatively rare, they often cause serious illness and death. These reactions are often not observed during conventional pharmacological and toxicological screening programmes and consequently account for many drug withdrawals from the market. Some examples are: malignant hyperthermia of anaesthesia, anaphylaxis due to penicillin, and many immunological reactions.
Limitations of Rawlins and Thompson classification: Some of the major limitations of Rawlins and Thompson classification are mentioned below:
1. Everything that is not type A is classified as type B, rendering the later a highly heterogenous group with little in common.
2. Certain ADRs do not fit into either category comfortably; hence it is difficult to decide whether such ADRs are type A or type B.
II. Wills and Brown classification: To overcome the limitations of Rawlins and Thompson classification, adverse reactions are classified into nine categories based on their mechanism. In this classification, the term ‘medicine’ has been used in preference to ‘drug’ to ensure that reactions secondary to the method of administration or excipients are clearly incorporated within the definition. Table 1 gives the types and common features of the ADRs as per the Wills and Brown classification.
Table 1. Wills and Brown classification of ADRs
S. No.
Classification of ADR
Type A (Augmented)

i. Relatively common
ii. Pharmacologically predictable
iii. Dose related
iv. Improves if medicine is withdrawn

i. Hypoglycemia with sulfonylureas
ii. Bradycardia with b- blockers, etc.
Type B (Bugs)
i. Involves interaction with a microorganism
ii. Pharmacologically predictable
iii. Improves if medicine is withdrawn

i. Dental caries with sugar coated tablets
ii. resistance due to overuse of any one antibiotic, etc.
Type C (Chemical)
i. Related to drug concentration
ii. An irritant reaction
i. Extravasation reactions
ii. Phlebitis, etc.
Type D (Delivery)
i. Caused by method of administration or nature of formulation
ii. Improves if medicine is withdrawn or method of delivery changed

i. Inflammation or infection around implant particles
ii. Infection at site of injection, etc.
Type E (Exit)
i. Pharmacologically predictable
ii.Begins only when the medicine is stopped or dose is reduced
iii. Improves if medicine is reintroduced
i. Withdrawal reactions due to opoids, benzodiazepines, clonidine, b- blockers, etc.
Type F (Familial)
 occurs only in the genetically predisposed
i. Hemolytic anemia with primaquin in G6PD deficient individuals, etc.
Type G (Genotoxicity)
causes irreversible genetic damage
i. Teratogenic agents like thalidomide causing genetic damage in the fetus, etc.
Type H (Hypersensitivity)
i. Requires activation of immune system
ii. Improves if medicine is withdrawn
i. Anaphylaxis with penicillin
ii. allergic skin reactions with antimicrobial agents, etc.
Type U (Unclassified)
Mechanism not understood  
i. Taste disturbances with simvastatin
ii. Nausea and vomiting with gaseous anesthetic, etc.


  1. Delivery Chemist
    Please Click below website here & Get Delivery Chemist

  2. Nice post! thanks for sharing this i really like it!
    For more see this site

  3. I'm glad you enjoyed the post.I’m really amazed with your posting skills as well as with the layout on your blog site.Very informative and well written post! Quite interesting and nice topic chosen for the post Nice Post keep it up.Excellent post.
    personalized medicine coalition

  4. My life is beautiful thanks to you, Mein Helfer. Lord Jesus in my life as a candle light in the darkness. You showed me the meaning of faith with your words. I know that even when I cried all day thinking about how to recover, you were not sleeping, you were dear to me. I contacted the herbal center Dr Itua, who lived in West Africa. A friend of mine here in Hamburg is also from Africa. She told me about African herbs but I was nervous. I am very afraid when it comes to Africa because I heard many terrible things about them because of my Christianity. god for direction, take a bold step and get in touch with him in the email and then move to WhatsApp, he asked me if I can come for treatment or I want a delivery, I told him I wanted to know him I buy ticket in 2 ways to Africa To meet Dr. Itua, I went there and I was speechless from the people I saw there. Patent, sick people. Itua is a god sent to the world, I told my pastor about what I am doing, Pastor Bill Scheer. We have a real battle beautifully with Spirit and Flesh. Adoration that same night. He prayed for me and asked me to lead. I spent 2 weeks and 2 days in Africa at Dr Itua Herbal Home. After the treatment, he asked me to meet his nurse for the HIV test when I did it. It was negative, I asked my friend to take me to another nearby hospital when I arrived, it was negative. I was overwhite with the result, but happy inside of me. We went with Dr. Itua, I thank him but I explain that I do not have enough to show him my appreciation, that he understands my situation, but I promise that he will testify about his good work. Thank God for my dear friend, Emma, I know I could be reading this now, I want to thank you. And many thanks to Dr. Itua Herbal Center. He gave me his calendar that I put on my wall in my house. Dr. Itua can also cure the following diseases ... Cancer, HIV, Herpes, Hepatitis B, Inflammatory Liver, Diabetis, Bladder Cancer,Colorectal Cancer,HPV,Breast Cancer,Kidney Cancer,Prostate Cancer,Glaucoma., Cataracts,Macular degeneration,Cardiovascular disease,Lung disease.Enlarged prostate,Osteoporosis.Alzheimer's disease,
    Dementia.Weak Erection,Love Spell,Leukemia,Lun,Fribroid,Infertility,Parkinson's disease,Inflammatory bowel disease ,Fibromyalgia, recover your ex. You can contact him by email or whatsapp, @ .., phone number .. + 2348149277967 .. He is a good doctor, talk to him kindly. I'm sure he will also listen to you.

  5. It is no secret that I have a very deep and personal relationship with God. I have pushed and resisted that relationship this past year through all the bullshit I have had to go through living with Herpes but once again, God is bigger than my stubbornness and broke through that outbreak cold sore and all I had Genital Herpes. For me personally, hearing over and over how I am not good enough has really invaded my mind in the worst way possible. I completely shut down and I was just waking up like is this how life going to end this temporary herpes outbreak “fuck everybody with herpes if you know what I mean” but let's be honest here...
    It is a cowardly to say no to herbal medicine. It is fear based. And it is dishonest to what my heart wants. Don't build a wall around yourself because you are afraid of herbals made or taking a bold step especially when it's come to health issues and getting cure. So many young men/ women tell me over and over that Dr Itua is going to scam me but I give him a try to today I feel like no one will ever convince me about herbal medicine I accept Dr Itua herbal medicine because it's cure my herpes just two weeks of drinking it and i have been living for a year and months now I experience outbreak no more, You can contact him if you need his herbal medicine for any such diseases like, Herpes, Schizophrenia,Cancer,Scoliosis,Fibromyalgia,Fluoroquinolone Toxicity Syndrome Fibrodysplasia Ossificans Progressiva.Fatal Familial Insomnia Factor V Leiden Mutation ,Epilepsy Dupuytren's disease,Desmoplastic,Diabetes ,Coeliac disease,Creutzfeldt–Jakob,,Lyme Disease,Epilepsy, ,ALS,Hepatitis,Copd,Parkinson disease.Genetic disease,Fibrodysplasia disease,Fibrodysplasia Ossificans Men/Woman infertility, bowel disease ,Huntington's disease ,Diabetes,Fibroid. disease,Lupus,Lipoid Storage diseases( Gauchers disease),Polycystic Disease.,Cerebral Amyloid Angiopathy, Ataxia,Cirrhosis of Liver,Arthritis,Amyotrophic Lateral Sclerosis,Alzheimer's disease,Adrenocortical carcinoma.Asthma,Allergic,HIV, Epilepsy, Infertility, Love Spell,. then what's app.+2348149277967.... My advice to any sick men/women out there is simple... Be Always an open book. Be gut wrenching honest about yourself, your situation, and what you are all about. Don't hold anything back. Holding back will get you nowhere...maybe a one way ticket to lonelyville and that is NOT somewhere you want to be. So my final truth...and I'm just starting to grasp this one..