Spontaneous reports of hypersensitivity adverse drug reactions in Portugal: a retrospective analysis

Background: Hypersensitivity adverse drug reactions (ADRs) are usually serious, unpredictable, and associated with high morbidity and mortality. This study describes cases of hypersensitivity ADRs spontaneously reported in Central Portugal. Methods: Spontaneous reports (SRs) of ADRs received between 2010 and 2017 were reviewed to identify cases of hypersensitivity reactions, using a Standardized MedDRA Query (SMQ). Seriousness, expectedness, and causality were assessed. Descriptive statistics were used to analyze data. Results: Among 2050 SRs, 598 (29.2%) contained 726 hypersensitivity ADRs: 657 (90.5%) serious, 569 (78.4%) unexpected, and 469 (64.6%) certainly related to drug exposure. Anaphylactic reactions (n = 93; 12.8%), rash maculopapular (n = 82; 11.3%), rash (n = 67; 9.2%) and DRESS (n = 54; 7.4%) were the most common reactions. Frequently implicated drug classes comprised antibiotics (n = 150; 23.0%), antineoplastic agents (n = 124; 19.0%), antigout preparations (n = 54; 8.3%), and anti-inflammatories (n = 44; 6.8%). Top-causative drugs were allopurinol (n = 54; 8.3%), docetaxel (n = 46; 7.1%), and trimethoprim/sulfamethoxazole (n = 26; 4.0%). Conclusions: Most hypersensitivity ADRs were serious, unexpected, and with strong causal relationship with suspected drugs. Allopurinol was the top-causative drug. Besides antibiotics and anti-inflammatories, antineoplastic agents were frequently cited. These results deserve further investigation.