anaphylaxis and drug allergy Flashcards
define hypersensitivity
objectively reproducible symptoms or signs, initiated by exposure to a defined stimulus at a dose tolerated by normal subjects and may be caused by immunologic (allergy) and non immunological mechanisms
2 types of anaphylaxis
immunological or non immunological
what is type 1 hypersensitivity
IgE mediated drug hypersensitivity
what is type 2 hypersensitiviy
IgG mediated cytotoxicity
what is type 3 hypersensitivity
immune complex deposition
what is type 4 hypersensitivity
T cell mediated
describe type 1 hypersensitivity
Acute anaphylaxis
Prior exposure to the antigen
IgE becomes attached to mast cells or leukocytes, expressed as cell surface receptors
Re-exposure causes mast cell degranulation and release of pharmacologically active substances
describe type 2 hypersensitivity
Antibody dependent cytotoxicity
Drug or metabolite combines with a protein
Body treats it as a foreign protein and forms antibodies
Antibodies combine with the antigen and complement activation damages the cells
describe type 3 hypersensitivity
Immune complex mediated
Small blood vessels are damaged or blocked
Leucocytes attracted to the site of reaction release pharmacologically active substances leading to an inflammatory process
describe type 4 hypersensitivity
Lymphocyte mediated
Antigen specific receptors develop on T-lymphocytes
Subsequent administration leads to local or tissue allergic reactions
define anaphylaxis
an acute allergic reaction to an antigen to which the body has become hypersensitive
4 main features of anaphylaxis
Exposure to drug, immediate rapid onset rash
Swelling of lips, face, oedema, central cyanosis
Hypotension
Cardiac arrest
3 ways to manage anaphylaxis
Commence basic life support
Adrenaline – IM 500µg
High flow oxygen
impact of adrenaline
Vasoconstriction – increase in peripheral vascular resistance,
increased BP and coronary perfusion
Stimulation of beta1-adrenoceptors positive ionotropic and chronotropic effects on the heart
Reduces oedema and bronchodilates via beta2-adrenoceptors
clinical criteria for allergy to drug
Does not correlate with pharmacological properties of the drug
No linear relation with dose (tiny dose can cause severe effects)
Reaction to similar to those produced by other allergens
Induction period of primary exposure
Disappearance on cessation
