Fixed drug eruption due to metronidazole

A 37-year-old woman was examined for a large, dark brown plaque on her left hip that had been present for three years and a second, similar plaque that had subsequently appeared on her right knee. Every four to five months the areas became swollen, red, and painful. She had been taking metronidazole intermittently for twenty years for the treatment of trichomoniasis; this drug on challenge proved to be the cause of the eruptions.     

Fixed drug eruption due to doxycycline and metronidazole

Fixed drug eruption (FDE) can be caused by an assortment of drugs. Although cross-sensitivity to 2 chemically related drugs has been frequently described, FDE to 2 unrelated agents rarely has been reported. To our knowledge, we report the first such case due to doxycycline and metronidazole.     

Topical provocation of fixed drug eruption

To determine whether topical provocation could be used for the diagnosis of fixed drug eruption (FDE) instead of systemic provocation, we applied the suspected drug at various concentrations (1-10%) in either petrolatum, 94% ethanol or dimethyl sulphoxide (DMSO) as an open test on both clinically normal skin and on previous FDE lesions in 24 patients with established FDE due to phenazone salicylate, a sulphonamide, doxycycline, trimethoprim, chlormezanone, a barbiturate, or carbamazepine. In 18 of the 24 patients, local provocation of FDE was seen at sites or previous eruption but never on clinically normal skin. With some drugs, e.g. phenazone salicylate, positive provocation of FDE was seen with all the vehicles used; with sulphamethoxazole and trimethoprim, a positive result was seen only in DMSO. To study cross-reactions to other phenazone derivatives in patients with an FDE caused by phenazone salicylate, we applied topical phenazone, aminophenazone and propyphenazone to sites of previous FDE lesions in three patients. In all three, a positive reaction was seen with phenazone, but only one patient showed positive results with aminophenazone and propyphenazone. The present study suggests that topical provocation is useful with several drugs causing FDE. Testing should always be performed on sites of previous FDE, and the sensitivity of the open topical testing can be increased in certain cases by using a vehicle which increases penetration of the drug.     

Fixed drug eruption in Nigeria

Fixed drug eruption (FDE) causes cosmetic embarrassment in Nigerian patients, particularly when the characteristic hyperpigmented patches affect the face and lips. Drugs that have been implicated in the etiology of FDE, and the sites of lesions, may vary from country to country. Antimalarials, such as Fansidar, Fancimef, Maloxine, Amalar, and Metakelfin, were the most common offending agents, accounting for 38% of FDEs, followed by trimethoprim + sulfamethoxazole (co-trimoxazole) (28%), dipyrones (10%), Butazolidin (6%), thiacetazone (6%), metronidazole (4%), paracetamol (3%), and naproxen (3%). Lesions induced by the combination of sulfadoxine and pyrimethamine (in antimalarials) mainly involved the face and lips. In most cases, patients took these sulfa-containing antimalarials in combination with numerous other drugs, particularly analgesics. Unlike chloroquine-induced pruritus, which affects most Africans, the association between antimalarials and FDE has not been well documented in our region. Co-trimoxazole was associated more often than antimalarials with FDEs involving the mucocutaneous junctions of the genitalia and lips. Males with genital lesions on the glans penis represented 11 (48%) of those with co-trimoxazole hypersensitivity. The trunk and limbs were affected mainly by pyrazoles and Butazolidin, respectively; however, solitary lesions on the trunk were usually due to co-trimoxazole, whereas solitary lesions on the limbs were associated with Butazolidin.     

Topical provocation in 27 cases of cotrimoxazole-inducedxed drug eruption

The purpose of this study was to investigate the usefulness of topical provocation in the diagnosis of cotrimoxazole-induced fixed-drug eruption (FDE). 27 patients with established cotrimoxazole-induced FDE by oral provocation and 20 healthy controls were tested with drugs at increasing concentrations in white petrolatum and dimethyl sulfoxide (DMSO) both on previously involved and uninvolved skin sites. Tape-stripping occlusive patch testing in petrolatum remained negative in 19 tested patients. Open testing with drug preparations in DMSO revealed positive results in 25 of 27 tested patients. 1 patient showed an additional positive reaction on previously uninvolved skin. Lesions on male genitalia and on face reacted to testing once with 10% or 20% of the suspected drug, whereas repeated testing with concentrations up to 50% was necessary in lesions on trunk & extremities. Open testing with drug preparations in DMSO at concentrations of 10%, 20% and 50% and pure DMSO remained negative in 20 healthy controls. The present study shows that repeated open testing with graded concentrations of the drugs up to 50% in DMSO is a reliable test method in sulfamethoxazole/trimethoprim-induced FDE. Patients and physicians should be aware of the transient irritant reaction to DMSO that is not infrequent, so as to avoid false-positive interpretations.