Development of a Natural Preservative System in Fluticasone Propionate Nasal Spray Formulation Using Eucalyptus globulus Essential Oil

Background: Replacing all or part of synthetic preservatives with natural antimicrobials in pharmaceutical formulations can be a way to improve the safety and quality of products. Evaluating the preservative effectiveness of essential oils is valuable since most of them are generally known to be safe. Objectives: In the current research, the efficacy of Eucalyptus globulus essential oil was investigated as an antimicrobial agent individually and in combination with benzalkonium chloride in fluticasone propionate nasal spray. Methods: To determine the minimum inhibitory concentration (MIC) of E. globulus essential oil, in vitro antimicrobial activity was assayed. The stability of nasal sprays was studied in intended preservation conditions at 40°C and RH: 25 %, and also the microbial challenge test was performed according to the United States Pharmacopoeia procedure, using reference strains: Staphylococcus aureus ATCC 1112, Escherichia coli ATCC 1330, Pseudomonas aeruginosa ATCC 1074, Candida albicans ATCC 5027, and Aspergillus brasiliensis ATCC 5011. Results: The combined application of E. globulus essential oil and benzalkonium chloride at a concentration of 0.675/0.005% v/v, in nasal spray formulation could decrease the bacterial and fungal populations, in compliance with United States Pharmacopoeia criteria, with considerable preservation within 28 days of the study compared to those preserved with only benzalkonium chloride (0.02%). Conclusions: In the current research, notable antimicrobial effectiveness of the combinational preservative system was observed and followed by a decrease in the functional level of the synthetic preservative. Therefore, after further studies, a combinational preservative system can be considered as an alternative preservative for pharmaceutical formulations.