Drug-Induced Hypersensitivity Reactions

Question 1

Define drug-induced hypersensitivity (DIHR)

Answer 1

A low frequency serious adverse drug reaction with an immunological etiology to an otherwise safe and effective therapeutic agent

Question 2

State the 4 key characteristics of DIHR

Answer 2

Rare
Unpredictable
Complex
Potentially fatal

Question 3

List the 2 types of DIHR

Answer 3

Immediate hypersensitivity
Delayed hypersensitivity

Question 4

Describe delayed hypersensitivity

Answer 4

Occurs in > 1 hour
Type IV or III
T cell-mediated

Question 5

Describe immediate hypersensitivity

Answer 5

Occurs within 1 hour
Type 1
IgE-mediated

Question 6

State the two primary reasons most people who claim to have an allergy to penicillin actually tolerate the drug

Answer 6

50% of people with IgE-mediated PCN allergy lose sensitivity within 5 yr; over 80% by 10 years
In some patients, the rash is caused by a concurrent viral infection

Question 7

State the two phases of delayed hypersensitivity reactions

Answer 7

Sensitization phase
(May occur through prior exposure or repeated dosing)

Effector phase

Question 8

Identify the most common organ affected by delayed hypersensitivity reactions

Answer 8

SKIN

Question 9

Define DRESS

Answer 9

Drug Reaction with Eosinophilia and Systemic Symptoms

Question 10

Describe DRESS

Answer 10

• Characterized by fever, skin rash, lymphadenopathy, hematological abnormalities, and internal organ involvement
• Onset 2-8 weeks after start of therapy
• ~10% mortality