Adverse Drug Reactions Flashcards
What is an adverse drug reaction (ADR)?
any undesirable or unintended effect following administration of a medical product, whether or not the effect is considered related to the medical product
When do ADRs usually resolve if not severe?
- when the drug is discontinued
- when the dose is reduced
- ADRs can diminish as the body adjusts to the drug
How should ADRs be categorized since they manifest in many forms?
It is helpful to categorize the reactions based on:
- type
- onset
- severity
What are two basic types of ADRs?
- pharmacological
- idiosyncratic
What is a pharmacological ADR?
- often predictable
- based on the drug’s mechanism of action
- typically dose-related
What is an idiosyncratic ADR?
- unpredictable
- may be more likely to result in mortality
What are idiosyncratic reactions mediated by?
- immune system
- receptor abnormalities
- drug–drug interactions
- abnormalities in drug metabolism
- pharmaceutical variations
- unmasking of an abnormal biological system
What is the most common way idiosyncratic reactions are mediated?
By the immune system when a drug molecule is recognized as a foreign substance
What are haptens?
- low-molecular-weight chemicals that can become antigenic when they covalently bind to a carrier molecule, which is usually a protein
- reacts specifically with an antibody but is incapable of stimulating antibody production except in combination with an associated protein molecule
What is an antigenic?
A substance that stimulates the production of an antibody when introduced into the body
What type of reaction does Penicillin, a hapten, produce?
Binds to a protein and results in a Type I hypersensitivity (anaphylaxis) reaction
What are the categories of immune-mediated hypersensitivity reactions?
- Type I
- Type II
- Type III
- Type IV
What is a Type I immune-mediated ADR? Give an example.
- IgE-mediated, immediate-type hypersensitivity
- Example: angioedema and anaphylaxis
What is a Type II immune-mediated ADR? Give an example.
- Antibody-dependent cytotoxicity
- Example: heparin-induced thrombocytopenia
What is a Type III immune-mediated ADR? Give an example.
- Immune complex hypersensitivity
- Example: Arthus reaction to tetanus vaccine
What is a Type IV immune-mediated ADR? Give an example.
- Cell-mediated or delayed hypersensivity
- Example: Drug Rash, Eosinophilia and Systemic Syndrome
How do medications that are not haptens able to elicit an immune-mediated reaction?
- through a different mechanism called the “pharmacologic interaction with immune receptors”
- there are chemically inert drugs, unable to covalently bind to proteins
- these medications are able to “fit” into major histocompatibility complex (a set of surface molecules) and the T-cell receptor sandwich
What is the definition on covalent?
relating to or denoting chemical bonds formed by the sharing of electrons between atoms
What are Type I immune-mediated reactions (IgE-mediated, immediate-type hypersensitivity) are provoked by?
- provoked by reexposure to an antigen.
- an acute hypersensitivity reaction that may be local or systemic
What does a Type I cell-mediated response involve?
Involves the:
- skin
- bronchopulmonary system
- nasopharnyx tract
- eyes
- gastrointestinal tract
What causes Type I cell-mediated responses?
It is caused by inducing the release of mediators (i.e., histamine, leukotrienes, and prostaglandins) from mast cells, basophils, and recruited inflammatory cells following antigen exposure, which then activates IgE.
How are Type I reactions managed?
Administration of:
- epinephrine
- antihistamines
- corticosteroids
What do Type II cell-mediated reactions affect?
In the bloodstream and on the surface of cells, antibodies unite with antigens or haptens and induce destruction of cells and tissues through activation of the complement system or through removal by macrophages.
