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Feature Articles : May 15, 2009 ( )
Nasal Administration Methods Stake Out Niche
A Standout among Noninjection Routes, Methodology Moves Forward Rapidly
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.
The majority of nasal products currently on the market address local conditions such as treatment of rhinitis and congestion. The nasal route provides a means for achieving rapid drug absorption and onset of therapeutic action, and is particularly advantageous for conditions where fast onset of action is needed. Currently available products in this category include sumatriptan, zolmitriptan, and ergotamine (migraine), and butorphanol (pain).
Other nasal products are available for drugs that are poorly absorbed by other routes of administration and have to otherwise be administered by injection—calcitonin (osteoporosis), nafarelin and buserelin (endometriosis), desmopressin (enuresis), cyanocobalamin (vitamin supplementation), and estradiol (hormone-replacement therapy).
While there is currently only one marketed intranasal vaccine, a live attenuated influenza antigen (FluMist®), many new intranasal drug and vaccine products are in development. The nasal delivery market is expected to continue to expand over the coming years with the arrival of new and improved products.
Although the nose is an attractive drug delivery target, not all therapeutic agents have the desired properties for optimal effect and there is still a need for innovative formulation technologies to enable the delivery of these sub-optimal compounds.
Among these innovations are Archimedes’ ChiSys®, an enabling technology for nasal drug and vaccine delivery that has been shown in preclinical and clinical studies to provide improvements in the intranasal bioavailability of drug compounds ranging from polar small molecules to peptides and proteins, as well as enhancing the immune response to nasal-administered vaccine antigens. Other nasal delivery technologies in development include CPE-215® (CPEX Pharmaceuticals) and Intravail® (Aegis Therapeutics).
Innovative systems are also needed for lipophilic drug compounds such as fentanyl with a short duration of action and/or where rapid and extensive absorption may be associated with undesirable side effects. Archimedes’ PecSys™ technology addresses this need and is currently used in NasalFent®, an intranasal fentanyl spray, which is delivered using a conventional nasal spray pump and forms a thin gel layer when sprayed into the nose, resulting in modulated drug absorption into the systemic circulation and an increased duration of action. NasalFent has successfully completed Phase III clinical trials and is expected to be approved in mid-2010.
Nasal drug delivery has compelling advantages over other delivery methods across drug classes and therapeutic indications. With a large surface area, a highly permeable epithelial membrane, an ability to avoid first-pass metabolism, and ready accessibility, the nasal route is seen as a highly promising means for rapid and effective delivery of drugs into the systemic circulation, especially in the treatment of crisis conditions where speed of onset of action is a key requirement.
These properties also mean nasal administration may offer an attractive alternative to injection for drugs that are otherwise poorly absorbed via other routes and for vaccines.
The true potential of nasal administration, however, is yet to be fully realized, largely the result of historical sub-optimal products, a failure to adopt enabling technologies, and an inability to identify the most appropriate circumstances and indications for nasal administration.
A new generation of nasal products is in development aimed at addressing these issues, many of which incorporate innovative delivery technologies, the key goal of which is to match the absorption and onset of action of the drug to the condition.
Nasal delivery also provides an attractive means for improving the commercial and therapeutic profile of well-established drug compounds, offering new product development opportunities with relatively low risk and a rapid development pathway.
For its future drugs, the pharmaceutical industry is increasingly looking to biotechnology. The resulting biological compounds typically have features that make delivery by the oral route problematic, such as high molecular weight and susceptibility to enzymatic degradation. Hence, injection is often considered the first or only option. The use of enabling technologies will allow the nasal route to be utilized as a viable alternative to injection for these compounds in the future and also offers exciting opportunities for nasally administered vaccines.
Alan Smith, Ph.D. (email@example.com), is vp of R&D at Archimedes. Web: www.archimedespharma.com.
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