Drug Reactions Lecture Flashcards
Common drugs
Penicillin Sulfonamides Barbiturates Anticonvulsants Insulin preps Local anesthetics Iodine preps
Prevalence and characteristics
1-5% experience cutaneous drug eruptions
No correlation with the diagnosis or underlying illness
Women»_space; men
Occur with previously tolerated drugs
Overlooked or misdiagnosed
Non-immunologic in nature (due to direct toxic effect on skin tissue or direct action to release histamine from mast cells and do not involve antibodies or T cells directly
Non-immunologic in nature means?
Due to direct toxic effect on skin tissue or direct action to release histamine from mast cells
Do NOT involve antibodies or T cells directly
Immune mediated allergic reactions
Drug-protein interactions may be mediated by metabolic enzymes and are processed by langerhans cells in skin (presented to T cells which produce TH1 or TH2 response)
Type 1 Gell-Coombs Classification
Classic immediate hypersensitivity - anaphylaxis
- Antibody: IgE mediated on mast cells and basophils
- Minutes to one hour
- Life-threatening
Type II Gell- Coombs Classification
Cytotoxic antibody reaction
- Antibody: IgE or IgM interacts with complement system resulting in cell lysis
- Within several hours
- Caused by drugs, food, emotions, environment
Type III Gell- Coombs Classification
Immune complex reaction
- Ige or IgM antibodies formed against drug to form an immune complex –> inflammation
Type IV Gell Coombs Classification
Delayed hypersensitivity reaction
- Sensitized T cells –> CYTOKINES and inflammation
- Late time course
- Drug induced skin rashes, cell mediated reactions (no antibodies)
- Stop ASAP, improves rapidly
Type V Gell Coombs Classification
Autoimmune response
- Antibody is produced and binds to some receptor in the body (self-antigen binding)
Type I Drugs
Epinephrine
Diphenhydramine (H1 blocker)
Hydrocortisone
Bronchodilators, IV fluids, and H2 antagonists
- Usually antihistamine and steroids
- 15% are H2 so just a H1 blocker wouldn’t do the job
Type II or III Drugs
H1 and H2 blocker (doxepin)
Hydrocortisone
Type IV Drugs
Mild and topical agents
- Oral antihistamine or corticosteroids
Exanthem
Rash
May be maculopapular, morbilliform, erythematous
- 2-3 days after drug admin
- Treated with an antihistamine, wet dressing or systemic corticosteroids
- Disappears after drug termination (2-4 days)
- Type IV
Urticarial eruptions
Hives
Treat with H1 and H2 blockers or systemic corticosteroids
Clear in 1-2 days
Fixed drug reaction
Oval lesion
Reoccur 30 minutes to 8 hours after rechallenge
Drugs not effective
Lesion heal 7-10 days after termination
Photosensitive
Senstivity to sun
Phototoxic: within hours of exposure
Photoallergic: within 1-2 days
Discontinue drug use
Alopecia
Toxic reaction
Interferes with normal growth phases of the hair
Acneiform eruptions
Acne like lesions, usually on neck, chest or back
2-4 week onset
Uniform size and symmetrical distribution
Erythema Nodosum
Red PAINFUL nodules
Discontinue drug
Heals over 2-3 weeks after termination
Exfoliative dermatitis
Severy with erthema and abundant flaky desquamation (skin sloughs)
Loss of fluids
Treat with fluids, steroids, pain meds and antibiotics
Toxic Epidermal Necrolysis (TEN)
Life threatening Medicated by cytotoxic T cells 30% mortality Discontinue drug use, use corticosteroids, antihistamines, fluids and antibiotics Severe pain Intensity: 1-3 days >30% of body
Stevens-Johnson Syndrome
Life threatening Mediacted by cytotoxic T cells Mortality rate 5-18% Symptoms: maculopapular bullae, vesicles, hemorrhagic lesions in the mouth, lips and conjunctiva Mild pain Intensity: 7-15 days <10% of body
Macule
Circumscribed, flat lesion of any shape or size
Differing from surrounding skin due to color
Papule
Small solid elevated lesion
