Toxicological investigations of the effects carboxymethylcellulose on ciliary beat frequency of human nasal epithelial cells in primary suspension culture and in vivo on rabbit nasal mucosa

The objective of this study was to investigate the safety of a mucoadhesive carboxymethylcellulose (CMC) formulation for intranasal administration of apomorphine. The effect of different concentrations of CMC on ciliary beat frequency (CBF) was studied using a human nasal epithelial suspension cell culture system. The CBF was determined by computerized microscope photometry. The in vivo rabbit nasal mucosal tolerance of the mucoadhesive polymer was investigated using light microscopy. Twice daily, six rabbits received CMC powder in one nostril and CMC/apomorphine powder in the alternate nostril for 4 weeks. Two control rabbits received air puffs in one nostril and nothing in the alternate nostril. The rabbits were subsequently sacrificed and the stained nasal sections examined microscopically. CMC showed both concentration- and time-dependent inhibitory effects on the CBF. Only mild-to-moderate cilio-inhibition was recorded with the different concentrations of the polymer. CMC (both with and without apomorphine) caused mild-to-moderate inflammation after 4 weeks. Necrosis, squamous metaplasia or ciliary degeneration was not observed. Based on: (1) the mild-to-moderate cilio-inhibition induced by different concentrations of CMC; and (2) the mild-to-moderate nasal mucosal inflammation caused by CMC with and without apomorphine, we conclude that this polymer can be considered as a safe carrier for short-term intranasal administration. However, further investigations are required for its use in the treatment of chronic diseases such as with apomorphine in Parkinson's disease.