Nasal preparations systemic action

If disturbances of gastrointestinal function prevent the use of oral sustained-release morphine, the fentanyl transdermal system (fentanyl patch) can be used over long periods. Furthermore, buccal transmucosal fentanyl can be used for short episodes of breakthrough pain (see Alternative Routes of Administration). Administration of strong opioids by nasal insufflation has been shown to be efficacious, and nasal preparations are now available in some countries. Approval of such formulations in the USA is growing. In addition, stimulant drugs such as the amphetamines have been shown to enhance the analgesic actions of the opioids and thus may be very useful adjuncts in the patient with chronic pain. 

Nasal preparations can be formulated as liquid, semisolid or solid preparations and can contain one or more active substances. Whether intended for local or systemic action, the mucociliary function of the nose should be disturbed as httle as possible by the preparation However, it is well known that active substances as weU as excipients may have a negative influence on the mucociliary clearance, in other words may be cdiotoxic. In the formulation of nasal preparations one should take into consideration the possible damage to the cilia in relation to the indication and the period of use. 

Generally speaking active substances with a systemic therapeutic action can be formulated as nasal preparations under the following conditions high water-solubUity (required dose must fit in 25-150 microlitres vehicle), sufficient chemical stability, no unpleasant smell or taste, favourable nasal absorption parameters, minimal nasal irritation and clinically important properties such as fast onset of therapeutic action, low dosage (normally less than 25 mg per dose), and no toxic metabolites [3, 8]. 

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