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Inhalation April 2023 41 nonclinical studies of nasal for- mulations and considerations in study design and methodology. e nasal architecture of a rat or dog is far more complex than that of a human, with different di- mensions and convolutions that impact greatly on administration, whether by instillation (placing of liquid into the nose) or insuf- flation (blowing or aerosolization of liquid or powder into the nasal cavity). As such, nonclinical reg- ulatory expectations are primarily around safety. e use of nasal de- vices is not necessary, provided the formulation remains in con- tact with the nose and (if intended for a systemic indication) the drug reaches the circulation. Translation of nonclinical findings to humans would benefit from more discern- ing methods for intranasal dosing of rodents, better understanding of drug distribution in vivo and techniques to provide greater in- sight into brain exposure. Clinical development Chris Roe, Quotient Sciences (UK), discussed clinical evalua- tion of nasally administered drug product performance by scintig- raphy/magnetic resonance im- aging (MRI). Gamma scintig- raphy quantifies deposition and clearance of formulations in the nasal cavity, which is demarcat- ed by MRI. If oral absorption is minimal, imaging data can be combined with pharmacokinetic (PK) and/or biomarker data ob- tained from the same study sub- ject to provide greater insight into product performance. A limita- tion is that radiolabels typically label the formulation rather than the drug. Clinical case studies in- cluded (i) comparison of nasal delivery by a pump spray, which was superior to a nebulizer and (ii) multi-day dosing of a chi- tosan formulation demonstrating retention in the nasal cavity with negligible delivery to the lungs. e challenge in sampling nasal fluid in clinical studies was also discussed, exemplified by a study www.inhalationmag.com Redesigned to increase its educational content, the Inhalation 1-2-3 e-newsletter provides a supplier's perspective on industry issues, highlights technical articles from the magazine and previews industry conferences. Please watch for it in your inbox every other month. Sign up now by emailing your name, company name and email address to subscriptions@inhalationmag.com.