Drug Reactions Flashcards
Drug induced skin reactions- IMMEDIATE reactions
- definition
- 3 examples
occur less than 1 hour of the last administered dose
Urticaria
Angioedema
Anaphylaxis
Drug-induced skin rxns- DELAYED reactions
- definition
- 4 examples
occurs after one hour, (U) more than 6 hrs later & occasionally weeks to months after start of administration
- exanthematous eruptions
- fixed drug eruption
- systemic reactions (DIHS, SJS, TEN)
- vasculitis
Role of Allergy in Cutaneous Reaction to Medications
Allergy testing (U) limited value
Penicillin is the exception to this rule
- “penicillin” skin testing is the preferred method of evaluation of possible type I, IgE-mediated penicillin allergy (urticarial due to penicillin)
- ideally, this testing also includes the major & minor determinant mixes (metabolites of penicillin)
The seven “I’s” in a complete drug history
- Instilled (eye drops, ear drops)
- Inhaled (steroids, beta adrenergic)
- Ingested (capsules, tablets, syrup)
- Inserted (suppositories)
- Injected (IV, IM)
- Incognito (herbs, non-traditional medicine, homeopathic, vitamins, over-the-counter)
- Intermittent (patients may not reveal medications they take on an intermittent basis unless specifically asked)
most important data in determining if a rash is medication-related
TIMING
Use of a drug timeline & how to do this
-drug timelines can help the dermatologist find likely medication causes
Day 0=onset of rash (start here & work backwards & forwards)
In exanthematous drug eruptions, meds (U) 7-10 days before the rash
[for repeat exposures, it may be much shorter]
Risk factors for drug reactions (5)
- Female
- Prior hx of drug rxn
- Recurrent drug exposure (repeated courses of drug=higher rates of adverse effects)
- HLA type:
SJS/TEN caused by allopurinol shows a strong association w/HLA-B 5801 in Han Chinese - Certain Disease States:
-rxns to aminopenicillins more (C) in pts w/Epstein Barr cirus (EBV) infection
-HIV+ pts have high rates of derm rxns to sulfonamides & other drugs
Exanthematous Drug Eruption: general d
-most (C) cutaneous drug eruption (~90%); limited to the skin
lesions initially on trunk & spread centrifugally to extremities in a symmetric fashion
- erythematous macules & infiltrated papules
- (P) pruritis & mild fever
- skin lesions (U) appear more than 2 days after drug has started [(U) around day 8-11 & occasionally persists 2-3 days after having stopped the drug]
Clinical Course of Exanthematous Drug Rxn
resolves a few days to a week after med is stopped
- if eruption is not too severe & med can’t be substituted you can continue the medication
- resolves without sequelae (though extensive scaling/desquamation can occur)
Tx of exanthematous drug rxns
topical steroids
oral antihistamines & reassurance
Fixed Drug Eruption definition
adverse drug rxn characterized by formation of a solitary erythematous patch or plaque
Drugs commonly involved in fixed drug eruptions (8)
- phenolphthalein
- tetracyclines
- metronidazole
- sulfonamides
- barbiturates
- NSAIDs
- salicylates
- food coloring (yellow)
Fixed Drug Eruption Distribution, Onset & Morphology
often affects mouth, genitalia, face & acral areas
if previously sensitized, lesions can occur 30mins-8hrs after ingesting the drug
early lesions: sharply demarcated erythematous macules
lesions become edematous, forming a plaque which may evolve to become a bulla and then an erosion
Fixed Drug Eruption treatment
lesions resolve days-few weeks after discontinuing drug
non-eroded lesions can be treated with a potent topical glucocorticoid ointment
