- Adverse cutaneous drug reactions (ACDRs) are unpredictable1. They affect 2% to 3% of inpatients and lead to 0.1% to 0.3% of hospital fatalities.
- In the United States, adverse drug events account for up to 140,000 deaths and $136 billion in costs annually.
- Most reactions are mild, accompanied by pruritus, and resolve promptly after the offending drug is discontinued.
- Drug eruptions can mimic virtually all the morphologic expressions in dermatology and must be the first consideration in the differential diagnosis of a suddenly appearing eruption.
- Drug eruptions are caused by immunologic or nonimmunologic mechanisms and are provoked by systemic or topical administration of a drug.
- The majority are based on a hypersensitivity mechanism and are thus immunologic and may be of types I, II, III, or IV.
Classification
IMMUNOLOGICALLY MEDIATED ACDR (see Table 23-1)
It should be noted that in most reactions both cellular and humoral immune reactions are involved. Nonimmunologic reactions are summarized in Table 23-2.
Guidelines For Assessment of Possible ACDRs
- Exclude alternative causes, especially infections (most commonly viral).
- Examine interval between introduction of a drug and onset of the reaction.
- Note any improvement after drug withdrawal.
- Determine whether similar reactions have been associated with the same compound.
- Note any reaction on readministration of the drug.
Findings Indicating Possible Life-Threatening ACDR
- Skin pain.
- Confluent erythema.
- Facial edema or central facial involvement.
- Palmar/plantar painful erythema.
- Epidermal detachment and blisters.
- Positive Nikolsky sign.
- Mucous membrane erosions.
- Urticaria.
- Swelling of the tongue.
- High fever (temperature >40°C).
- Enlarged lymph nodes.
- Arthralgia.
- Shortness of breath, wheezing, and hypotension.
- Palpable purpura.
- Skin necrosis.
Clinical Types of Adverse Drug Reactions
Adverse cutaneous drug reactions (ACDRs) can be exanthematous and can manifest as urticaria/angioedema, anaphylaxis, and anaphylactoid reactions, or serum sickness. They can mimic other dermatoses and they can also present as cutaneous necrosis, pigmentation, alopecia, and hypertrichosis. They can induce nail changes. An overview is presented in Tables 23-3 and 23-4.
1Skin reactions or changes regularly occurring after high dose or prolonged administration of certain drugs like glucocorticoids, retinoids, cyclosporine, and others are not discussed in this section but throughout the book whenever these drugs are discussed in greater detail.