Contact sensitivity to tioconazole and other imidazoles

Antifungal hypersensitivity reactions and cross-reactivity patterns

PURPOSE OF REVIEW

The goal of this article is to provide an updated understanding and evidence-based approach where possible for antifungal hypersensitivity. This includes recognition of clinical phenotype, implications for cross-reactivity and diagnostic, and management strategy for immediate and delayed hypersensitivity reactions.

RECENT FINDINGS

Antifungal hypersensitivity reactions can be classified according to their latency (immediate or delayed) and clinical phenotype. The majority of the cases described in the literature are delayed T-cell mediated reactions of various severities but immediate reactions consistent with non-Immunoglobulin E (IgE)-mediated mast cell activation and IgE-mediated reactions have also been described. Ancillary information such as skin testing, drug challenge and ex vivo experimental approaches can aid causality assessments and inform antifungal class cross-reactivity, which help optimize antifungal prescribing and stewardship.

SUMMARY

This review will update the clinician on mechanisms of drug hypersensitivity as well as providing a structured approach to the recognition, diagnosis and management of antifungal hypersensitivity reaction.

Anaphylaxis to proton pump inhibitors

Proton pump inhibitors (PPI) are widely used for the treatment of peptic ulcer, but cases of anaphylactic reactions have rarely been described. We present a patient who experienced an episode of urticaria 30 minutes after oral intake of an omeprazole capsule. Skin prick tests to omeprazole, pantoprazole and lansoprazole were positive. Challenge test with lansoprazole was carried out and within 45 minutes the patient developed urticaria, facial edema, vomiting, and hypotension. Oral challenge with other imidazole derivatives (ketoconazole, cimetidine, metronidazole) were carried out with good tolerance. Serum tryptase levels determined 3 hours after the adverse reaction to lansoprazole were elevated. Specific IgE to PPI were not detected by an enzyme-linked immunosorbent assay technique. The clinical findings, positive skin prick test to PPI and elevated serum tryptase levels suggest that an IgE-mediated mechanism was implicated in the reactions to both omeprazole and lansoprazole. Skin prick tests may be a useful tool for detecting patients sensitized to PPI. An experimental protocol was used to detect specific IgE antibodies against PPI, which may explain RAST negativity. The previous findings suggest that cross-reactivity between PPI exists, but not with other imidazoles.

A study of 72 patients with contact allergy to tioconazole

Over a 3 1/2 year period, from 1991 to 1994, we detected contact allergy to tioconazole in 72 patients by epicutaneous testing. During this period, tioconazole was included in the standard series of epicutaneous tests. Except for the first 6 months, the incidence of positive patch test reactions to tioconazole was over 1% of patients tested for contact allergy. As well as those tested with the standard series, 18 additional patients with tioconazole allergy were detected by direct testing with an imidazole patch test series. Of the various imidazole derivatives, tioconazole was the most important contact allergen. About half of patients with contact hypersensitivity to tioconazole, had additional contact allergies detected by the standard series. Men and women were equally affected. The present study suggests that tioconazole is an important contact allergen, which should be included into the patch test series in countries where it is used as a topical antifungal agent.

Contact allergy to imidazoles used as antimycotic agents

The present article reviews the literature (up to 1994) on contact sensitivity to imidazoles and presents the results obtained from 15 patients observed at the Contact Allergy Unit in Leuven. The frequency as well as the cross-reaction patterns described are analyzed. Although allergic contact reactions may have been missed in the past (mainly because of problems with the correct choice of vehicle for patch testing), they seem to be relatively infrequent in view of their widespread use. The imidazole derivatives most frequently reported to be allergens are miconazole, econazole, tioconazole, and isoconazole. As far as cross-reactivity is concerned, statistically significant associations were found in the patient data between miconazole, econazole, and isoconazole; between sulconazole, miconazole, and econazole; and also between isoconazole and tioconazole. Patients sensitive to phenylethyl imidazoles (except ketoconazole) needing antimycotic therapy should be advised to use ketoconazole, clotrimazole, bifonazole, or, perhaps, the new flutrimazole. Clearly, non-imidazole antifungals can also be used.