Flucloxacillin formulation odour acceptability: A human sensory assessment

Palatability influences a medicine's acceptability. While medicine's taste and their acceptability have been explored, the relationship between a medicine's odour and its acceptability has received less attention. In this study, the odour acceptability of a range of oral flucloxacillin formulations was assessed by healthy adult volunteers. Flucloxacillin was chosen as it is reported to be malodourous and found to be poorly palatable by children. The odour of a commercial flucloxacillin solution and capsule formulation were rated as acceptable. The commercial solution odour was described as fruity, and aromatic, while the commercial capsule was described as odourless. An unformulated flucloxacillin solution and flucloxacillin minitablets were deemed to have an unacceptable odour described as pungent, musty, plastic, and rotten. The odour of flucloxacillin minitablets including silica was deemed as odourless and acceptable. The ability of silica to suppress flucloxacillin's malodour was attributed to its adsorption of malodourous volatile compounds. Malodourous volatile sulphur compounds, produced during flucloxacillin degradation, were identified by GC-MS in the headspace of an unformulated flucloxacillin solution. The volunteers' smell acuity was assessed and found to be normosmic or microsmic, except for one volunteer who was anosmic (odour blindness). While the odour assessments of normosmic and microsmic volunteers generally aligned, the anosmic volunteer's assessments were contrary to the general findings. This study highlights the ability of formulation to improve the odour acceptability of flucloxacillin, it demonstrates the capability of silica to suppress drug malodour, and determines the importance of volunteer smell acuity screening during medicine odour sensory studies.