Clinical relevance of drug-drug interactions in hospitalized dermatology patients.

BACKGROUND: Potential drug-drug interactions (DDIs) are known to be a risk factor for the development of adverse drug reactions (ADRs). Data on the occurrence of ADRs related to DDIs is scarce and comes from different groups of patients. OBJECTIVES: The aim of the study was to evaluate the frequency, nature and determinants of potential DDIs in hospitalized dermatology patients and assess their contribution for the development of ADRs. MATERIAL AND METHODS: A prospective observational study comprising all consecutive inpatients admitted to the Clinic of Dermatology and Venereology, University Hospital, Stara Zagora for the period March 2009 - August 2011 was carried out. Systemic medication was screened for potential DDIs using an electronic drug interactions checker. DDIs were then verified with Stockley's Drug Interactions and divided into "clinically important" and "clinically unimportant". ADRs were classified by clinical manifestation, type and severity. Causality was scored according to Naranjo et al. (1981). RESULTS: The study included 674 patients, 513 (76.1%) of them with established comorbidities. Totally, 504 potential DDIs were identified (441 "clinically important" and 63 "clinically unimportant") in 236 patients. Hypotension was the most common expected clinical presentation of the potential DDIs. The strongest predictor for the development of DDIs was the number of systemic drugs (OR 2.25, 95% CI 1.97-2.58). Overall 43 ADRs were recorded, 53.5% "type B" and 46.5% "type A" reactions, most commonly with cutaneous and cardiovascular manifestations. The development of ADRs was attributed to 13 DDIs (2.6% of all detected potential DDIs) in 10 of these cases (23.25%). CONCLUSIONS: Potential DDIs were frequent in hospitalized dermatology patients. The drug groups most commonly involved were cardiovascular drugs. The proportion of DDIs associated with the occurrence of ADRs was relatively low, but close monitoring of patients on multiple drug regimens is essential because these reactions may be severe.

Carbamazepine-induced drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome: report of four cases and brief review.

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare but severe drug reaction, most commonly to aromatic anticonvulsants with a delayed onset, variable clinical presentation and protracted course. The exact incidence of DRESS syndrome is not known because of the variability in clinical presentation, lack of strict diagnostic criteria and universally accepted nomenclature. We report four cases of DRESS syndrome associated with the use of carbamazepine. The clinical manifestation was similar: a maculopapular eruption progressing to exfoliative erythroderma, fever, and lymphadenopathy. Leukocytosis, atypical lymphocytes and liver injury (in 2 patients) were also observed. Assessment of causality using the Naranjo algorithm established a "probable" relationship with carbamazepine in three of the cases and a "possible" relationship in one case. Detection of DRESS syndrome is dependent on the exclusion of a variety of diseases with similar manifestations and may be delayed in time. DRESS syndrome is a potentially life-threatening multisystem adverse drug reaction, and accidental reexposure or drug provocation tests must be avoided.