RESUMO
OBJECTIVES: This study aimed to retrospectively assess whether community pharmacy customers accepted the pharmacist's recommendations for the selection of an antihistamine based on medicine optimization guidelines. METHODS: A retrospective study was conducted on the implementation of an antihistamine use optimization guide for patients who were seeking first-generation antihistamines between July and December 2019 across forty-five community pharmacies in Singapore. The primary outcome measure was the acceptance rate of ceasing or substituting first-generation antihistamine with a second-generation antihistamine. Secondary measures included the reduction in types of first-generation antihistamines used, adverse drug-related events reported, intended use of antihistamines and the types of recommendations. KEY FINDINGS: During the study period, 2328 patients fulfilled the inclusion criteria, out of which 523 patients agreed to optimize their use of sedating first-generation antihistamines. Chlorpheniramine (95.2%) was the most widely accepted first-generation antihistamine for optimization, with 59.6% of the users experiencing adverse events, the most common being drowsiness (53.2%). The main indication of use was allergic conditions (allergic rhinitis or atopic dermatitis) (70.3%). After implementation of the guide, most interventions were direct substitution (72.8%) with a less-sedating antihistamine, followed by gradual tapering (22.6%). Loratadine, a second-generation antihistamine, was most frequently (51.4%) used to substitute first-generation antihistamines. The optimization guide can potentially reduce adverse effects in 59.6% (297 patients) of chlorpheniramine users, which were mainly drowsiness (265 patients; 53.2%) and dry mouth (14 patients; 2.8%). CONCLUSIONS: This study highlighted the importance of assessing and reducing potentially inappropriate first-generation antihistamine self-use and that a guided approach and substitution with less-sedating antihistamines can be employed in the community pharmacy setting.
