Microbiological Quality and Preservative Efficacy Testing of Marketed Oral Liquid Paediatric Formulations in Ibadan, Oyo State

Oral liquid paediatric formulations are among the most vulnerable pharmaceutical products to microbial contamination due to their aqueous base, high sugar content, and repeated opening during use. In Ibadan, Oyo State, a major pharmaceutical distribution hub in South West Nigeria, a wide variety of these products are available across different retail channels. This study evaluated the microbiological quality and preservative efficacy of eight commercially available paediatric oral liquid formulations including syrups and suspensions. Microbial enumeration was performed on freshly opened and in-use samples using standard pour plate techniques for total aerobic microbial count, total yeast and mould count, and specific pathogen testing as per USP microbiological standards. Preservative efficacy was assessed using the USP challenge test with organisms including E. coli, Pseudomonas aeruginosa, S. aureus, Candida albicans, and Aspergillus brasiliensis. Three products failed the total microbial count limits in the in-use samples, and two failed preservative efficacy testing against Candida albicans. Products from smaller domestic manufacturers showed higher rates of non-compliance compared to multinational brands. These findings highlight the need for enhanced microbial quality controls and preservative system validation in Nigerian paediatric pharmaceutical manufacturing. Keywords: paediatric formulations, microbiological quality, preservative efficacy, oral liquids, Ibadan.