DRUG ERUPTIONS

Most common are maculo-papular exanthema’s, which are usually itchy.
Drugs with a > 1‰ incidence of drug-induced exanthema are: penicillins,
sulphonamides (fansidar, trimethoprim), NSAID’s (like aspirin,
indomethacin), isoniazid, erythromycin, hydantoin derivatives (e.g. phenytoin),
carbamazepine, allopurinol, streptomycin and gold salts. They
may occur soon after taking the drug (in previously sensitised patients),
on finishing a course of drugs, or up to 3 weeks after taking a drug.
Urticaria is also a common reaction, often caused by penicillins,
NSAID’s, acetylsalicylic acid and X-ray contrast media.
Fixed drug eruptions recur on exactly the same spot every time the
responsible drug is taken. There is usually one, sometimes two or more
macules or plaques, reddish-purple in colour. They may show blistering
and leave persistent hyperpigmentation on healing. Most frequent
causes: barbiturates, paracetamol, pyrazolon derivatives, sulphonamides
and tetracyclines.
Some drugs cause photosensitivity, commonly implicated are:
amiodarone, chlorothiazide, fluoroquinolone derivatives, NSAID’s,
phenothiazines, psoralens, sulphonamides and tetracyclines.
Stevens-Johnson syndrome and toxic epidermal necrolysis are
serious blistering eruptions which may affect large areas of skin and
mucous membranes and may be fatal. Common causes: sulphonamides,
hydantoins, pyrazolon derivatives, carbamazepine and NSAID’s.
Erythema exsudativum multiforme (EEM) shows characteristic
"target" or "iris" lesions and is considered a minor form of Stevens
Johnson syndrome. EEM and Stevens-Johnson syndrome are commonly
caused by herpes simplex infections, only in second instance by drugs
and other infections such as mycoplasma infections.
Patients with HIV-infection are more susceptible to all drug eruptions.
Nearly all drugs can cause drug eruptions. Only the most commonly
implicated drugs have been mentioned here.
Management of drug eruptions
- Identify the responsible drug and stop the use of that drug.
- For itchiness and drying in: Calamine lotion with or without menthol 0.25% and/or
phenol 1% , or zinc oxide cream.
- Burn cream or honey.
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- Oral antihistamines e.g. promethazine 25 mg once or twice daily or
chlorpheniramine 4 mg 3 times daily.
- In severe reactions a short course of prednisolone may be given starting at 30-60 mg
daily and quickly reducing the dose in 2 weeks.
- When there is extensive skin loss the patient should be hospitalised, given i.v. fluids
and treated like a burn case i.e. given betadine baths, dressed with silver
sulphadiazine 1% burn cream and given antibiotics and analgesics as required.