adverse effects of drugs

Adverse Drug Reactions: Types, Examples, and Prevention

This article explains the five types of adverse drug reactions (ADRs) and how to prevent them. It also provides examples and statistics of ADRs.

Adverse drug reactions are unwanted or harmful effects of drugs that occur after taking a normal dose. 

They can range from mild symptoms, such as nausea, rash, or headache, to severe reactions, such as anaphylaxis, liver failure, or death. 

Adverse drug reactions can affect anyone who takes drugs, but some people are more at risk than others. 

For example, older people, children, pregnant women, and people with chronic diseases or multiple medications are more likely to experience adverse effects of drugs

In this blog post, we will discuss the types and examples of adverse drug reactions and how to prevent them.

What are the five types of adverse drug reactions?

ADRs can be classified into five types according to their mechanisms and characteristics:

Type A (Augmented)

These are the most common and predictable ADRs. They are caused by an exaggeration or extension of the normal pharmacological action of the drug. 

They are usually dose-dependent and related to the drug’s potency and efficacy. They can be mild, moderate, or severe. 

Examples of type A ADRs include bleeding from blood thinners, low blood sugar from diabetes medications, and drowsiness from sedatives.

Type B (Bizarre)

These are uncommon and unpredictable ADRs. They are not related to the dose or the pharmacological action of the drug. They are caused by an abnormal or hypersensitive immune response to the drug or its metabolites. 

They can be mild or life-threatening. Examples of type B ADRs include allergic reactions, such as anaphylaxis, rash, and hypotension, from antibiotics, aspirin, or contrast agents.

Type C (Chronic)

These are ADRs that occur after long-term or repeated use of a drug. They are usually dose-dependent and time-related. 

They are related to the cumulative effects of the drug on certain organs or systems. They can be reversible or irreversible. 

Examples of type C ADRs include osteoporosis from corticosteroids, liver damage from alcohol, and kidney damage from NSAIDs.

Type D (Delayed)

These are ADRs that occur after a long latency period following exposure to a drug. They are usually not dose-dependent or time-related. 

They are related to the delayed effects of the drug on certain tissues or cells. 

They can be reversible or irreversible. Examples of type D ADRs include cancer from chemotherapy agents, birth defects from thalidomide, and thyroid dysfunction from amiodarone.

Type E (End-of-use)

These are ADRs that occur when a drug is discontinued or withdrawn. They are usually dose-dependent and time-related. 

They are related to the loss of the drug’s therapeutic effect or the rebound of the underlying condition. 

They can be mild or severe. Examples of type E ADRs include withdrawal symptoms from opioids, benzodiazepines, or antidepressants, and relapse of seizures from antiepileptics.

adverse effects of drugs

How to prevent adverse drug reactions?

ADRs can be prevented by following some simple steps:

Keep a list of your medications

Write down all the medications you take, including prescription drugs, over-the-counter drugs, herbal remedies, supplements, and vitamins. 

Include the name, dose, frequency, and reason for each medication. Update your list whenever you start or stop a medication. Share your list with your doctor, pharmacist, and other health care providers.

Follow directions

Read the label and the patient information leaflet carefully before taking any medication. Follow the instructions on how to take, store, and dispose of your medication. 

Do not take more or less than prescribed. Do not skip doses or stop taking your medication without consulting your doctor.

Ask questions

If you have any doubts or concerns about your medication, ask your doctor or pharmacist for clarification. 

Ask about the possible benefits, risks, side effects, interactions, and precautions of your medication. Ask what to do if you miss a dose or experience an ADR.

Keep up with any blood testing

Some medications require regular blood tests to monitor their levels or effects on your body. 

These tests can help adjust your dose or detect any problems early. Follow your doctor’s advice on when and how to do these tests.

Take all medications only as directed

Do not share your medication with others or use someone else’s medication. Do not use expired or damaged medication. 

Do not mix your medication with alcohol or other substances that may affect its action. Do not crush, chew, or break tablets or capsules unless instructed by your doctor or pharmacist.