August 26, 2015 - Allergy Flashcards
(12 cards)
Idiosyncratic Adverse Reaction
The cause of unknown. We don’t know why it happened.
Class Effect
All related drugs exhibit the same “reaction”.
Multiple Drugs and Toxicities
Don’t double-stack the toxicities of drugs. This greatly increases the chance and severity of an adverse effect.
Type 1 Hypersensitivity
Anaphylactic reaction. Mediated primarily through IgE.
May be de-sensitized if the drug must be used by starting with a very small dose and working your way up. This causes gradual degranulation of mast cells and basophils rather than them all dumping at once.
Type 2 Hypersensitivity
Cytotoxic.
Mediated by IgG or IgM. Results in the hemolysis of RBCs, WBCs, platelets, etc.
The antibody WITH the drug binds to a cell. Just the Ab by itself, or just the drug itself isnt a problem, but when they mix together it causes a cytotoxic effect.
Type 3 Hypersensitivity
Occurs when antigen-antibody complexes are not adequately cleared and they accumulate, giving rise to an inflammatory response. These may become deposited in tissues and cause inflammation.
Mediated by IgM or IgG.
Type 4 Hypersensitivity
Delayed type hypersensitivity. This is mediated by cells, rather than antibodies. Helper T cells recognize the antigen in a complex with the APC macrophages and invoke an immune response. Macrophages are activated and cause an inflammatory response which ultimately leads to tissue damage.
Treatment of Type 1 Hypersensitivity
ALWAYS stop the offending agent first
Phone a friend
If mild, use steroids, anti-histamines, and block histamine release.
If severe, use epinephrine and always go to the hospital because the effects of the epinephrine are often less long-lived than the offending agent.
Mononucleosis and Amoxicillin
If infected by EBV and are given amoxicillin, 40% of patients will develop a rash. They are not allergic to the amoxicillin.
Side-Chain and Allergies
Most allergies are associated with the side chain rather than the core structure. The side chain can be used to predict cross-reactivity with other drugs that contain a similar side chain.
Steven-Johnson Syndrome
Is a form of toxic epidermal necrolysis in which the epidermis seperates from the dermis. It is caused rarely by some medications.
If less than 10% of the skin, it is considered Steven-Johnson Syndrome. If more than 30% of the skin, it is known as Toxic Epidermal Necrolysis.
Patients must be treated like a severe burn patient. It affects the mucus membranes, so if a patient presents with a rash, ALWAYS check the inside of the mouth. Discontinue the drug if anything is in the mouth.
