Pediatric emergency medicine trisk 1305 1305
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while EM typically first appears on the hands and feet before progressing
centrally.
The treatment for drug-induced urticaria is withdrawal of the causative
medication and treatment with both H1- and H2-blocking oral antihistamines for
up to 4 to 8 weeks. For cases that persist despite maximum dosing of nonsedating
H1- and H2-blocking antihistamines, oral steroids may be beneficial.
MORBILLIFORM
Morbilliform, or measles-like, describes an eruption characterized by both
erythematous macules and papules ( Fig. 68.3 ). The term “maculopapular” is
often used to describe this eruption, but morbilliform is a more precise
description. This is the most common type of drug rash. The eruption typically
starts on the trunk before spreading to involve the extremities and face, though
the mucous membranes are spared. The eruption can become diffuse and
confluent. Pruritus may be present.
A morbilliform drug eruption typically appears 7 to 14 days after medication
initiation, but in a previously sensitized patient it may appear within hours to days
of reexposure. Antibiotics, in particular penicillins ( Fig. 68.4 ), cephalosporins,
sulfonamides, and antiepileptics are common triggers.
A morbilliform drug eruption can be difficult to clinically distinguish from a
viral exanthem. One unique example is that of the morbilliform eruption that may
result from antibiotic administration, most commonly amoxicillin, during an
Epstein–Barr virus (EBV) infection. Although early studies reported an incidence
of 90% or more, a more recent study suggests that the true incidence is closer to
30%. This eruption, however, is not actually a drug hypersensitivity reaction
(DHR), but rather is a viral exanthem.
Treatment involves a balance between the severity of the eruption and the
importance of the causative medication. The rash is generally self-limited and
will resolve within 7 to 14 days of stopping the medication. However, if the rash
is mild and the medication is essential, then the medication can be continued with
close monitoring. Morbilliform drug eruptions do not progress into more severe
drug reactions, however, severe drug reactions may mimic a morbilliform drug
eruption early on. Therefore, an uncomplicated morbilliform drug eruption must
be distinguished from DHR, which has systemic involvement. If the eruption
appears within the first 2 weeks of starting a medication, then it is more likely to
be a morbilliform drug eruption. If the eruption is delayed by several weeks, then
DHR is more likely. The presence of additional clinical features, such as facial
edema and lymphadenopathy, and laboratory findings can also aid in
