The effect of the nasal cycle on mucociliary clearance.

The nasal cycle is a well-recognised physiological phenomenon where each side of the nose alternates through phases of congestion and decongestion. Although many physiological properties of the nose alternate with the nasal cycle whether this has any effect on the nasal mucociliary clearance is less clear. As the nose is a potential site for the administration of pharmaceuticals, it is essential that any factors that could affect clearance (and hence absorption) are identified. This study set out to investigate if mucociliary clearance rates differed between the clear and obstructed airway at a morning peak of the nasal cycle in five healthy volunteers with normal nasal anatomy using a dual-radioisotope labelling procedure that allows both sides of the nose to be assessed simultaneously. The clearance of the radiopharmaceutical formulations from the nasal cavity was monitored using gamma scintigraphy and decay-adjusted 50%-clearance times were calculated for each nostril. The ratios of clearance times from the patent nostril when compared to the obstructed nostril were statistically significant (two-tailed t-test; P = 0.039), the mean ratio being 2.5 : 1 (SEM +/- 0.5). It can be concluded that the nasal cycle has a marked effect on the mucociliary clearance patterns of the nose. This may have both theoretical and practical implications for the nasal delivery of drugs.