Physiological Pharmaceutics

Nasal drug delivery 205penetration and infection of host cells. Viruses are able to disrupt clearance by penetratingthe mucosa and cause degeneration and shedding of epithelial cells. Once this damage hasoccurred, the nasal mucosa is open to bacterial infection by normal commensals.Cold sufferers exhibit both markedly increased and decreased mucociliary clearancerates. During the hypersecretory phase (rhinorrhea) the clearance is increased and usuallyduring recovery from a cold there is congestion which slows clearance 17 . The susceptibilityto rhinoviruses in women is significantly related to the menstrual cycle, possibly due tochanges in mucociliary function during the cycle 18 .Allergic rhinitis may be acute and seasonal (hayfever) or chronic (perennial rhinitis).In an allergic person, substances such as pollen or dust may more readily penetrate in andthrough the surface epithelium. Hayfever is the most common of all allergic diseases,affecting an estimated 10% of the population. The allergy to pollen producesrhinoconjunctivitis, for which the main symptoms are an itchy nose, sneezing and wateryrhinorrhea. Mucus clearance time is decreased because nasal secretions become alkaline (pH8) leading to increased ciliary activity 19 . There is an increase in water transport towards theepithelial surface and an altered transepithelial potential difference 20 . The same mechanismsare true for the increase in clearance seen in perennial allergic rhinitis where dust and fumesor some other allergen can provoke sneezing, rhinorrhea and nasal blockage. Thephysiological reaction to aerial contamination is of such a degree that it exceeds theselfcleaning capacity of the nose, impairing the nasal filter function.AsthmaAsthmatics and bronchiectasis sufferers, both with and without allergic rhinitis, have anincreased nasal mucociliary clearance time. It is therefore thought that there is some sort ofmucus abnormality and ciliary malfunction working in concert 21 . Observations inasthmatics of tracheal mucus transport rates suggest that the mucociliary dysfunctionobserved after antigen challenge is related to airway anaphylaxis (a hypersensitivityreaction) and its chemical mediators. Pretreatment with sodium cromoglycate, a mast cellstabiliser, prevents the expected antigen induced increase in clearance time, but histaminealone is probably not the main mediator, since it stimulates mucociliary clearance. Analternative possible mediator is known as slow-reacting substance of anaphylaxis (SRS-A).SinusitisChronic sinusitis is the sequela to acute inflammation. Any condition that interferes withdrainage or aeration of a paranasal sinus renders it liable to infection. If the ostium of a sinusis blocked, mucus is accumulated and pressure builds up. The nasal clearance time isincreased in this condition due to the increase in quantity of mucus, which is usually highlyviscous and adhesive 12 . However the inflammatory response is associated with changes inthe H + concentration of the nasal mucus, and nasal secretions tend to be alkaline in reaction,therefore increasing ciliary activity 19 .Kartegener’s syndromeKartegener’s syndrome is an inherited disorder which comprises transposition of some orall of the major organs, bronchiectasis and sinusitis. The syndrome may also be associatedwith a variety of structural and functional abnormalities of cilia (the immotile cilia or ciliarydyskinesia syndrome), common due to a deficiency of the dynein arms which normallygenerate microtubule movement 22 . Mucociliary flow rate is therefore decreased due tociliostasis. As well as the defects in nasal cilia associated with genetic disorders, evaluationof cilia from patients with chronic sinusitis, nasal polyposis, rhinitis and cystic fibrosis hasdemonstrated multiple membrane, microtubular and radial spoke alterations, although theimportance of these in the pathologies is not known 2 .