Drug Reactions Flashcards
What are the preformed mediators in mast cells?
Proteases (tryptase, chymase), heparin, histamine
What are the synthesized mediators in mast cells?
prostaglandins, leukotrienes, platelet activating factor, cytokines
If a pediatric patient gets DRESS on phenytoin for seizures, what medication should they be switched to and what ones should they not be transitioned to?
Can transition to Valproic acid, there is no cross-reactivity.
There is cross-reactivity with all aromatic anticonvulsants = phenytoin, carbamazepine, and phenobarbitol
How are cutaneous drug reactions divided?
Simple (no visceral/systemic involvement) and complex (systemic involvement)
What is the prevalence of severe cutaneous adverse reactions among patients with drug reactions?
2% (SJS/TEN, DRESS/DHS, AGEP, anaphylaxis anticoagulant-induced skin necrosis, and generalized fixed drug)
What are the most common morphologies of drug rash?
Morbilliform (92%)>>>urticarial (6%)>vasculitis (2%)
When are HIV patients at the highest risk of getting cutaneous drug reactions?
Increased risk across the board, but the highest risk occurs when the CD4 count is 100-400/mm3.
What are the most common causes of cutaneous drug rash in patients with HIV?
TMP/SMX (rash in 40% of HIV pts), dapsone, beta-lactams, nevirapine, abacavir, and anticonvulsants
What is the timing of a morbilliform drug rash?
7-14 days after drug initiation (cell-mediated hypersensitivity)
What are the most common culprits of morbilliform drug rash?
Beta-lactams, TMP/SMX, anticonvulsants, and allopurinol
What viral infections significantly increase the risk of rash from medications?
HIV: especially true for TMP/SMX (40%)
EBV: ampicillin in pts w/ EBV-mononucleosis gives rash in all children and 70% of adults
What is the clinical presentation of a morbilliform drug rash?
The rash starts w/ red-pink macules and papules in the groin/axilla and later progress to symmetrically-distributed red macules and papules on the trunk and upper extremities often w/ pruritus (note that viral exanthems aren’t usually pruritic)
- Rash becomes more confluent over time and the lesions on the lower extremities can have a purpuric component
Doesn’t affect mucous membranes, no facial edema, no peripheral eosinophilia, no dusky/painful lesions on the skin
What is the progression of simple morbilliform drug rash?
Clears after 1-2 weeks after drug cessation (will also stop if the drug is continued… doesn’t progress to angioedema/more serious reaction in vast majority of pts)
What is the histology of a simple morbilliform drug reaction?
MIld basal vacuolar and spongiotic changes w/ few necrotic keratinocytes (50%). Can have superficial to mid dermal perivascular lymphohistiocytic infiltrate w/ some eos
What is the prognosis of Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
10% mortality
What is the timing of Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Occurs later, 2-6 weeks after initiation of a drug
What are the most common sx’s in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Fever (85%), morbilliform skin eruption (75%), arthralgias (>arthritis), multi-organ involvement (liver is most common and severe followed by kidney), peripheral eosinophilia (>1500 absolute eos), mononucleosis-like atypical lymphocytosis
What is the usual progression of the rash in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Starts on the face and upper trunk/extremities; appears morbilliform but can become more edematous (facial edema is important early sign), with follicular accentuation and you can have tense vesicles or bullae, pustules, and purpuric lesions
What are the late sequelae that can occur in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Thyroiditis/Graves, SIADH, and diabetes
Can occur up to a year out from initial rash
What virus is thought to be involved in the pathogenesis of Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
HHV-6 reactivation (>HHV-7, CMV, and EBV)
What is the most common classes of meds that are known to cause Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Aromatic anticonvulsants (phenytoin, carbamazepine, and phenobarbital), lamotrigine (especially when coadministered w/ valproate), sulfonamides, minocycline, dapsone, allopurinol, abacavir, and nevirapine
Which medications are more likely to affect the liver in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Dapsone, Minocycline, aromatic anticonvulsants
Which medications are more likely to cause cardiac issues in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Ampicillin, minocycline
Which medications are more likely to cause renal damage in Drug-induced hypersensitivity syndrome/Drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS)?
Allopurinol, carbamazapine, dapsone