Understanding adverse drug reactions and their causes

Adverse drug reactions can occur when starting a medication, changing a dosage, or even after discontinuing use. These reactions may be known side effects or unexpected, severe responses that require professional medical evaluation.

Factors influencing individual responses include age, genetics, general health status, and dosage. Interactions with other substances, such as different medications, food, or dietary supplements, can also play a role. In rare instances, issues may stem from defective or counterfeit products.

Reactions are categorized into several types:

Type A reactions are common and occur when a drug's physiological action becomes excessive, such as bleeding from an anticoagulant. Type B reactions include allergic responses like rashes, swelling, or breathing difficulties. Type C reactions are related to long-term use, Type D reactions appear with a delay (months or years after exposure), and Type E reactions occur following the cessation of a drug.