Lecture 38 Flashcards
Drug-induced hypersensitivity
low frequency serious adverse drug reaction with an immunological etiology to an otherwise safe and effective therapeutic effect
Key characteristics of DIHR
- Rare
- Unpredictable
- Complex
- Potentially fatal
Hapten
a low molecular weight chemical with the propensity to bind irreversibly to
protein. A hapten might or might not stimulate an immune response
Immediate hypersensitivity
occur within 1 hour
type 1
IgE mediated
Delayed hypersensitivity
Occurs more than an hour
type 4 or 3
T-cell mediated
State the two primary reasons most people who claim to have an allergy to penicillin actually tolerate the drug
10% population claim PCN allergy
90% of those stated to have a PCN allergy can tolerate the drug
50% of people with IgE-mediated PCN allergy lose sensitivity within 5 years; more than 80% by 10 years
in some patients the rash is caused by concurrent viral infection
Two phases of delayed hypersensitivity
- sensitization phase may occur through prior exposure or repeated dosing
- effector phase
hapten/antigen reexposure
Identify the most common organ affected by delayed hypersensitivity reactions
Skin is the most common target of DIHR
10-30% of ADR involve the skin
serious cutaneous adverse reactions occur at low frequency
Time frame of drug eruptions
Exanthemas (90%)
onset 4-14 days after start of therapy
last about a week
self-limiting
often caused by viruses
associated with many drugs
Erythema multiforme, SJS, TEN
onset 1-3 weeks after start of therapy
allopurinol, carbamazepine, nevirapine
DRESS
characterized by fever, skin rash, lymphadenopathy, hematological abnormalities, internal organ involved which is different from other DIHRs
10% mortality
onset 2-8 weeks after start of therapy
antibiotics, anticonvulsants, allopurinol
