Referring to FIG. 1, the nasal airway 1 comprises the two nasal cavities separated by the nasal septum, which airway 1 includes numerous ostia, such as the paranasal sinus ostia 3 and the tubal ostia 5, olfactory cells and is lined by the nasal mucosa. The nasal airway 1 can communicate with the nasopharynx 7, the oral cavity 9 and the lower airway 11, with the nasal airway 1 being in selective communication with the anterior region of the nasopharynx 7 and the oral cavity 9 by opening and closing of the oropharyngeal velum 13. The velum 13, which is often referred to as the soft palate, is illustrated in solid line in the closed position, as achieved by providing a certain positive pressure in the oral cavity 9, such as achieved on exhalation through the oral cavity 9, and in dashed line in the open position.
There are many nasal conditions which require treatment. One such condition is nasal inflammation, specifically rhinitis, which can be allergic or non-allergic and is often associated with infection and prevents normal nasal function. By way of example, allergic and non-allergic inflammation of the nasal airway can typically effect between 10 and 20% of the population, with nasal congestion of the erectile tissues of the nasal concha, lacrimation, secretion of watery mucus, sneezing and itching being the most common symptoms. As will be understood, nasal congestion impedes nasal breathing and promotes oral breathing, leading to snoring and sleep disturbance. Worryingly, the incidence of such allergic and non-allergic inflammatory diseases is increasing. Other nasal conditions include nasal polyps which arise from the paranasal sinuses, hypertrophic adenoids, secretory otitis media, sinus disease and reduced olfaction.
In the treatment of certain nasal conditions, the topical administration of medicaments is preferable, particularly where the nasal mucosa is the prime pathological pathway, such as in treating or relieving nasal congestion. Indeed, topical administration is advantageous in minimizing the possible side effects of systemic administration. Medicaments that are commonly topically delivered include decongestants, antihistamines, cromoglycates, steroids and antibiotics.
There are now an increasing number of adults and children who rely on pharmaceuticals to relieve symptoms associated with nasal conditions. At present, among the known anti-inflammatory pharmaceuticals, topical steroids have been shown to have an effect on nasal congestion. Topical decongestants have also been suggested for use in relieving nasal congestion. The treatment of hypertrophic adenoids and chronic secretory otitis media using topical decongestants, steroids and anti-microbial agents, although somewhat controversial, has also been proposed. Further, the topical administration of pharmaceuticals has been used to treat or at least relieve symptoms of inflammation in the anterior region of the nasopharynx, the paranasal sinuses and the auditory tubes.
Aside from the delivery of medicaments, the irrigation of the nasal mucosa with liquids, in particular saline solutions, is commonly practiced to remove particles and secretions, as well as to improve the mucociliary activity of the nasal mucosa. These solutions can be used in combination with active pharmaceuticals.
Furthermore, medicaments are now increasingly systemically delivered through the nasal pathway, the nasal pathway offering a good administration route for the systemic delivery of pharmaceuticals, such as hormones, for example oxytocin, and antimigraine compositions, as the high blood flow and large surface area of the nasal mucosa advantageously provides for rapid systemic uptake.
A variety of delivery systems have been developed to deliver substances to the nasal airways of subjects.
Conventionally, spray bottles have been used to deliver a medicament-containing liquid or an irrigating liquid to the nasal airways of subjects. However, the distribution of the delivered substance, in particular to the posterior region of the nasal airway, is less than ideal, especially in the cases of moderate and severe nasal obstruction. This poor distribution is often further exacerbated by a subject inhaling through the nasal airway during delivery, as is often prescribed, in an attempt to deliver the substance to the posterior region of the nasal airway. Indeed, an amount of the substance can be drawn into the lungs or swallowed in each delivery, which could be problematic in paediatric subjects if the medicament is a potent pharmaceutical, such as a steroid, which has to be administered frequently. In addition, the spray is frequently directed against the nasal septum which can undesirably lead to localized deposition. Further, the mechanical action of the delivery mechanism of the spray bottles can cause irritation and bleeding.
GB-A-408856 discloses a delivery device, which, in one mode of use, allows for the inhalation of separate air flows entraining medicament into respective ones of the nasal cavities of a subject. This delivery device comprises a chamber containing a sponge saturated with medicament, a mouthpiece connected to the chamber and first and second nosepieces connected to the chamber. In one mode of use, the nosepieces are fitted into respective ones of the nostrils of a subject, and, on inhalation through the nosepieces, air flows entraining medicament are drawn into the lungs of the subject. In another mode of use, the mouthpiece is taken in the mouth of a subject, and, on inhalation through the mouthpiece, an air flow entraining medicament is drawn into the lungs of the subject.
WO-A-98/53869 discloses a delivery device for delivering a powder containing a medicament to the nasal mucosa in one of the nasal cavities of a subject. This device comprises a tubular section which contains a metered dose of powdered medicament. In use, the ends of the tubular section are respectively located in the nostril of one of the nasal cavities and the mouth of a subject, and on exhalation by the subject through his or her mouth the exhaled air entrains the powdered medicament and delivers the same into the one nasal cavity, with the exhaled air backflowing out of the one nostril around the tubular section. In one embodiment the tubular section includes a flexible portion upstream of the dose of powdered medicament. The provision of this flexible portion allows the subject to close the tubular section at a point upstream of the medicament, such that, on release of the closed flexible portion during exhalation, a short explosive air flow entraining medicament is delivered into the one nasal cavity. In another embodiment the end of the tubular section located in the nostril can be shaped to act to locate the tubular section in a position in the nostril which allows for the deposition of the powdered medicament on the nasal mucosa.
Whilst this delivery device is simple in construction, the operation of the device still does not provide for the effective delivery of substances, in particular one of a liquid or powder containing medicament, to the posterior region of the nasal airway, since medicament is delivered separately to each of the nasal cavities and the air flow into and out of each nasal cavity is through the same opening, namely the respective nostril, with the closed posterior region of the respective nasal cavity acting as a pressure reflecting surface which causes the exhaled air to backflow out of the one nostril before ever adequately reaching the posterior region of the respective nasal cavity. Further, in providing a short explosive burst of air flow into one of the nasal cavities, it is not possible to achieve a sustained and controlled bidirectional air flow through the nasal cavities which has been found necessary to deliver a substance effectively to the posterior region of the nasal airway.
For any substance to be delivered effectively to the nasal airway, it is highly desirable that the administration is efficient and simple. However, there can be problems in attempting to achieve this goal. In particular, the pathological changes observed with nasal inflammation make administration of substances, such as liquids or powders, tricky, particularly to the posterior region of the nasal airway and the posterior margins of the nasal structures. Indeed, as a consequence of the complex geometry of the narrow slit-like passages in the nasal airway, these passages become partially occluded when the nasal mucosa is inflamed and congested, making the distribution of topical pharmaceuticals to the nasal airway difficult.