Pharmaceutical companies have recognised the advantages of nasal delivery and extended both their product development and the demands on devices to efficiently deliver substances that are potentially more potent and expensive. Chris Halling reports.
Although currently a small fraction of the rapidly expanding drug delivery market, nasal devices are increasingly being considered as a vehicle for delivering active substances non-invasively for rapid onset. This growth is fuelled by a combination of factors including the shift away from traditionalCFC-propelled inhalers as well as the recognition that the nasal cavity is a good route for systemic as well as locally acting therapies.
Indeed, the nasal cavity provides several benefits as a drug delivery route. Drug uptake through its highly vascularised sub-epithelial layer avoids the body's first-pass metabolism and enables therapies to be absorbed directly into the systemic circulation. Avoiding exposure to the hostile gastro-intestinal tract also reduces the likelihood of drugs denaturing, hence the nasal cavity offers the opportunity to deliver delicate biological molecules such as proteins. Nasal delivery can also provide anon-invasive delivery solution for drugs that suffer poor oral bioavailability and offers patients obvious advantages over parenteral administration.
With the potential for delivering a wider range of therapeutic agents such as proteins, peptides and vaccines, accurate shot-to-shot consistency becomes of greater importance. As it is likely that some more innovative therapies will have shorter shelf-life and less frequent or irregular dosing regimes, Bespak developed UniDose DP which employs a sealed, single shot drug container and provides highly accurate and reliable levels of shot to shot consistency. The product provides active delivery of the drug (ie when actuated it uses mechanically compressed air to expel the drug powder) and is therefore less prone to vagaries in the user's delivery technique than a pump spray. In tests, UniDose DP consistently provided more than 96 per cent delivery efficiency of the metered dose in a single actuation.
Developments such as UniDose DP show how device/spray characteristics can be optimised to further enhance delivery to the surface of the nasal cavity. However, the challenge facing the drug delivery community is achieving similarly high levels of performance using multiple-dose devices. Work is being undertaken at Bespak to support this development and the company has invested in advanced equipment such as a sheet laser from Oxford Lasers to ascertain and analyse device performance very accurately. Using this equipment in conjunction with high-speed video, the company can assess detailed device spray characteristics.
However, the success of drug delivery through the nasal passage will increasingly necessitate a deep understanding of the nasal anatomy. Only detailed knowledge of the specific structure and complexities of the nasal cavity can translate into enhanced particle deposition and, therefore, increased availability. Close work with the CIIT Centers for Health Research, who are leading figures in respiratory and inhalation science, is also well underway to maximise the efficacy andcost-effectiveness of nasal drug delivery by developing devices that ensure the correct dose is accurately administered to the correct area within the extensive and complex nasal cavity.
Bespak anticipates that the success of this work will significantly enhance the nasal delivery ofhigh-value, systemic drugs. Continued improvements in the repeatability of shot consistency could even result in a challenge to the more invasive methods of drug delivery, promoting the nasal passages from a minor to a major drug delivery route in future.
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Chris Halling is with Bespak Europe, Milton Keynes, Buckinghamshire, UK. www.bespak.com
