Nasal drug delivery mechanisms

For nasal drug delivery, it has been suggested that two mechanisms of absorption exist, based on the physicochemical properties of the drug ... 

A number of adjuvants are awaiting approval for human use. The main impediment to the successful development of vaccine adjuvants is that their mechanism of action is not clearly understood. Table 5 offers a fist of available nasal drug delivery systems and the various adjuvants that have been used in the development of nasal vaccines. 

Nasal drug delivery devices can be divided into multidose and unit-dose/bi-dose systems. Multidose systems consist of a container mounted with a mechanical pump dispenser that is designed to deliver multiple doses from one container (Fig. 1). The various requirements of the customer and of the formulation are respected in the design and performance of the delivery systems. Unit-dose and bi-dose systems are becoming increasingly attractive to the pharmaceutical industry. In particular, therapies that require precise performance in their delivery system employ these single/ dual-use disposable systems. 

The entire nasal cavity is lined by pseudostratilied squamous epithelium with a cover of a thin layer of mucus providing immune and mechanical protection. Cilia beat in the mucus about 1000 times per minute and surface material is moved along at a rate of 3-25 mm/min. This transport is unidirectional and moves mucus and any trapped inhaled particles back toward the nasopharynx, where it is periodically swallowed. Drug delivery to the lung is therefore likely to be markedly reduced in the presence of excess mucous seCTetion. Further details of the anatomy and physiology of the nasal cavity can be found in published reviews (24,29,30). 

Marttin, E., J.C. Verhoef, and F.W. Merkus. 1998. Efficacy, safety and mechanism of cyclodex-trins as absorption enhancers in nasal delivery of peptide and protein drugs. J Drug Target 6 17. 

The type of nasal device employed in delivering a drug formulation plays a major role in the efficacy of the treatment. In general, two types of delivery systems are used mechanical pumps and pressurized aerosol containers. The properties of the drug to be used influence the selection of the system. The various types of delivery devices are described in the following sections. 

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