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Year : 2022  |  Volume : 67  |  Issue : 3  |  Page : 315
Drug patch testing in patients of fixed drug reaction due to fluoroquinolones-imidazole combination

Department of Dermatology, NKP Salve Institute of Medical Sciences and Lata Mangeshkar Hospital, Nagpur, Maharashtra, India

Date of Web Publication22-Sep-2022

Correspondence Address:
Sushil Pande
Department of Dermatology, NKP Salve Institute of Medical Sciences and Lata Mangeshkar Hospital, Nagpur, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijd.IJD_627_20

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How to cite this article:
Rathi S, Pande S, Borkar M. Drug patch testing in patients of fixed drug reaction due to fluoroquinolones-imidazole combination. Indian J Dermatol 2022;67:315

How to cite this URL:
Rathi S, Pande S, Borkar M. Drug patch testing in patients of fixed drug reaction due to fluoroquinolones-imidazole combination. Indian J Dermatol [serial online] 2022 [cited 2022 Sep 30];67:315. Available from:


Fixed-drug reaction (FDR) is a characteristic cutaneous adverse drug reaction that recurs at a specific site or at different sites each time a specific drug is taken. FDR being a delayed type of cutaneous adverse drug reaction, drug patch test is suggested to help identify the exact culprit drug.[1] There have been conflicting reports of the utility of drug patch testing in patients of FDR and in other forms of cutaneous adverse drug reaction (CADR). The current study was conducted with an attempt to evaluate the usefulness and safety of the drug patch testing in FDR caused exclusively due to fluoroquinolone-imidazole drug combination.

A total of 30 consenting patients of fixed-drug reaction caused definitely due to fluoroquinolone-imidazole combination were included in a prospective study at a tertiary care and a referral center in central India after the permission from the institute's ethics committee. Causality as “definite” was established using Naranjo's algorithm for causality assessment, and only patients with “definite” causal association were enrolled in the study.[2]

Patch testing was conducted between the 6 weeks and 6 months period after complete resolution of fixed drug eruption, as per the suggested guidelines given by the International Contact Dermatitis Research (ICDR) group.[3] The patch test material was prepared in 10% and 30% drug concentration in white soft paraffin base in the Department of Pharmacology. The patch test material formulated included suspected fluoroquinolone, imidazole, and a combination of fluoroquinolone-imidazole in 10% and 30% concentration as per the type of fluoroquinolone and imidazole taken by the patient. This was applied using Finn's chamber on the lesional skin. The first reading was done at the end of 48 h after the patches were removed and the second reading was recorded on day 7 according to the criteria laid down by the ICDR group. An independent expert evaluator who was blinded for patch test drug application interpreted results of drug patch testing.

However, no positive results were observed in any patients on day 2 and day 7. No side effects were noted. Thus patch testing with fluoroquinolone, imidazole, and/or a combination of both were not positive in all 30 patients of FDR with 10% and 30% drug patch tests and did not elicit positive patch test reaction.

Among the various reasons for negative patch test results, one reason for negative patch tests in our study may be a sensitization or allergy to drug metabolites rather than the original drug that was used for patch testing. The patch tests using the commercialized form may give false-negative results because these metabolites are usually neither known nor available for patch tests.[4] Additionally, the false-negative results may be attributed to low concentrations of the drug used in patch testing. In most cases, patch tests are performed with the drug mixed in petrolatum to 10%–20% or diluted in water at the same concentration. To overcome this, we also used a 30% drug patch test formulation to enhance drug concentration despite which patch tests were negative in our study. Although positive patch test reactions can be more easily obtained with the drug diluted to 50%, this should not be done because stronger delayed reactions would occur on days 3–7, indicating patch test sensitization. Finally, false-negative results may result from the limited penetration properties of the drug. A study concluded that a positive patch test reaction confined to the previously involved sites is considered as strong evidence that the FDE lesions are caused by the drug, although a negative test does not exclude it.[5] The rates of positivity of drug patch test depend on the causative drug as well, rather than the type of reaction as is reported by Ohtoshi et al.[6]

The findings of our study of negative patch testing with fluoroquinolones and imidazoles are consistent with observations by different investigators with this group of drugs. Our study concludes that patch testing with 10% and 30% concentration of fluoroquinolones and imidazole in lesional skin of fixed drug reaction fails to elicit a positive reaction and thus is not able to detect the etiological agent responsible for it. We recommend further studies of patch testing in fixed drug reaction to confirm our observations. For etiological diagnosis, oral provocation test may be required.


The lack of availability of commercialized or readymade patch test kits for patch testing.

Further studies are required for patch testing in confirmed cases of fixed drug reaction due to fluoroquinolones-imidazole combination to know the positivity rates for identifying the culprit drug.

Patch testing in patients of other non-immediate cutaneous adverse drug reactions due to fluoroquinolone-imidazole combination is recommended.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Pinho A, Coutinho I, Gameiro A, Gouveia M, Gonçalo M. Patch testing - A valuable tool for investigating non-immediate cutaneous adverse drug reactions to antibiotics. J Eur Acad Dermatol Venereol 2017;31:280-7.  Back to cited text no. 1
Naranjo CA, Busto U, Sellers EM, Sandor P, Ruiz I, Roberts EA, et al. A method for estimating the probability of adverse drug reactions. Clin Pharmacol Ther 1981;30:239-45.  Back to cited text no. 2
Wilkinson DS, Fregert S, Magnusson B, Bandmann HJ, Calnan CD, Cronin E, et al. Terminology of contact dermatitis. Acta DermVenereol 1970;50:287-92.  Back to cited text no. 3
Shiohara T. Fixed drug eruption: Pathogenesis and diagnostic tests. Curr Opin Allergy Clin Immunol 2009;9:316-21.  Back to cited text no. 4
Friedmann PS, Ardern-Jones M. Patch testing in drug allergy. Curr Opin Allergy ClinImmunol 2010;10:291-6.  Back to cited text no. 5
Ohtoshi S, Kitami Y, Sueki H, Nakada T. Utility of patch testing for patients with drug eruption. Clin Exp Dermatol 2014;39:279-83.  Back to cited text no. 6


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