Recent advances in drug delivery have led to significant innovations including polymer implants, transdermal patches, and sophisticated oral controlled-release formulations. These technologies, although in widespread use today, were primarily developed to provide sustained delivery of drugs and thereby reduce dosing frequency. Alongside these now-mainstream technologies, other alternative routes for introducing drugs into the body have also been exploited. As it has long been known that drugs can be absorbed into the systemic circulation through the oral and nasal cavities and lungs, these routes have generated great interest.
The need to solve the delivery problems associated with newly developed drugs and to create drug formulations that better serve patient needs and disease treatment has intensified the search for alternative delivery methods. As these new delivery routes have gained acceptance, technologies have been developed to expand the range of drugs that can be administered.
Vaccine delivery is also entering a new era, with alternative delivery modes to traditional injections being developed for both patient convenience and to enhance safety and efficacy.
The nasal route can be used both for local treatment of disease (e.g., allergic rhinitis and nasal congestion) and to administer therapeutic agents for systemic absorption and action.
As a route for systemic drug delivery, the nose is readily accessible and is a convenient and noninvasive way to administer drugs. The underlying epithelium is highly vascularized, and blood passes from the nose directly into the systemic circulation. As a result, nasally administered drugs will be readily absorbed into the bloodstream, avoiding first pass metabolism and providing rapid therapeutic effect.
Nasal administration is particularly attractive when rapid treatment is required—for critical medical conditions and where rapid symptom relief is a key aim, for example breakthrough cancer pain. Additionally, nasal administration avoids exposure to digestive enzymes, a problem when attempting to administer peptide and protein drugs orally, and offers the potential for injection-free administration of these therapeutic agents.
The nasal route is particularly attractive for vaccine administration. The nose has its own nasal-associated lymphoid tissue that is accessible for immunization. Nasal immunization has significant advantages over conventional parenteral delivery of vaccines, as both systemic and mucosal immune responses are generated. Nasal vaccination can obviate the need for needles and syringes, encouraging greater public compliance, and, at times of a pandemic, is well-suited to rapid mass vaccination programs.
Although other noninjection delivery routes claim similar advantages, nasal administration stands out for many reasons. Nasal absorption is faster, more complete, and significantly more convenient compared to oral transmucosal (buccal/sublingual) administration; compared to pulmonary delivery, nasal delivery is simpler, is independent of patient technique, and requires less expensive and complex delivery devices.