Unwanted drug effects/Anaphylaxis

Unwanted drug effects

Any noxious or unintended reaction to a drug that has been given at a standard dose by an approved route for the prevention, treatment or diagnosis of a condition.

Unwanted drug effect

Any noxious or unintended reaction to a drug that has been given at a standard dose by an approved route for the prevention, treatment or diagnosis of a condition.

-Adverse drug reactions are probably responsible for 3-5% of all hospital admissions.

This can be divided according to:

-Reactions that can occur in anyone

-Reactions that occur in susceptible individuals, including genetic variation

-Allergic reactions

Numerous ways of classifying adverse drug reactions are discussed later in the session

Types of adverse drug reactions- Drug overdose

An overdose is a toxic reaction linked to an excess dose or to impaired excretion, or both.

For example, the use of long-acting opioids in patients with renal failure, or a prescription resulting in an error in dosing of insulin.

Types of adverse drug reactions- Drug side-effect

A side-effect is an undesirable pharmacological effect that happens at recommended doses. For example, constipation with opioids or tachycardia with cyclizine.

Drug interaction

Drug interaction is the action of a drug on the effectiveness or toxicity of another drug.

Anaphylaxis

A rapid-onset, IgE-mediated hypersensitivity reaction that occurs when the immune system mistakenly identifies a drug as a harmful invader.

-This leads to mast cell degranulation and systemic histamine release, triggering severe reactions that require immediate intervention.

Anaphylaxis example

Anaphylaxis from Amoxicillin

•Mechanism: In a sensitized individual, re-exposure to a beta-lactam antibiotic leads to a massive immune response, causing vascular collapse, airway swelling, and bronchoconstriction.

Symptoms of anaphylaxis

-Skin: Rapid onset of urticaria (hives), itching, or angioedema.

-Respiratory: Wheezing, stridor, throat tightness, dyspnoea.

-Cardiovascular: Hypotension, tachycardia, dizziness, syncope.

Onset: Develops within minutes to one hour of drug exposure.

Anaphylaxis is characterised by:

-Sudden onset and rapid progression of symptoms.

-Airway and/or Breathing and/or Circulation problems.

-Usually, skin and/or mucosal changes (flushing, urticaria, angioedema).

-The diagnosis is supported if a patient has been exposed to an allergen known to affect them. However, in up to 30% of cases there may be no obvious trigger

-Skin or mucosal changes alone are not a sign of anaphylaxis. Skin and mucosal changes can be subtle or absent in 10–20% of reactions