Epidermal necrolysis (EN)--either Stevens-Johnson syndrome (SJS) or toxic EN (TEN)--is a severe drug reaction. We constructed and evaluated a specific algorithm, algorithm of drug causality for EN (ALDEN), in order to improve the individual assessment of drug causality in EN. ALDEN causality scores were compared with those from the French pharmacovigilance method in 100 cases and the case-control results of the EuroSCAR study. Scores attributed by ALDEN segregated widely. ALDEN pointed to a "probable" or "very probable" causality in 69/100 cases as compared to 23/100 with the French method (P < 0.001). It scored "very unlikely" causality for 64% of medications vs. none with the French method. Results of ALDEN scores were strongly correlated with those of the EuroSCAR case-control analysis for drugs associated with EN (r = 0.90, P < 0.0001), with probable causality being reported in 218/329 exposures. ALDEN excluded causality in 321 drugs that the case-control analysis had described as "probably not associated" and in 22/233 drugs that had been described as inconclusive exposures. Being more sensitive than a general method, ALDEN, which correlates well with case-control analysis results, can be considered a reference tool in SJS/TEN.

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The hospitalised patients in a cardiological hospital (Lille, France) over an 18-month period were subjected to a prospective high-intensity adverse drug reaction (ADR) monitoring in order to assess the additional financial resource utilisation associated with ADRs and analyse the distribution of excess of cost according to ADR nature and therapeutic classes. Over 18 months, among the 16,916 hospitalised patients, 371 verified ADRs detected by self-report stimulated by a special unit of nurses and pharmacologists occurred in 336 patients with an overall ADR rate of 2.2%. This rate increased with age. The most common reactions were cutaneous events (24%), cardiovascular events (21%), metabolic disorders (12%), coagulation disorders (10%) and nervous system impairment (10%). The most common drug classes involved were cardiovascular agents (36%), contrast media (20%), drugs affecting blood clotting (13%) and anti-infectives (14%). Increased ADR-induced costs result especially from prolongation of length of stay and cost increase was evaluated at Euro 4150 per ADR. Among the 371 ADRs, 134 ADRs, which were significantly more severe, induced a prolongation of length of stay. Renal insufficiency and cardiovascular events were significantly over-represented in this sub-group. The most common ADR-inducing drugs associated with a prolongation of length of stay are cardiovascular agents and drugs affecting blood clotting. In contrast, cutaneous ADRs were significantly over-represented in the group of ADRs without prolongation of length of stay. The severity and substantial costs of ADRs in hospital justify investments to prevent these events. Nevertheless, only a portion of ADRs induces cost increases, suggesting that prevention efforts should focus on this limited category of ADRs.

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