Role of Nasal Casts for <i>In Vitro</i> Evaluation of Nasal Drug Delivery and Quantitative Evaluation of Various Nasal Casts

<b>Background:</b> Nasal casts may characterize intranasal drug deposition. <b>Methodology:</b> The Koken cast, described as 'anatomically correct', and the Optinose cast, derived from MRI of a healthy male during velum closure, were dimensionally compared and assessed for deposition assessment suitability. <b>Results:</b> Smallest vertical cross-sectional areas (valve region) for Koken and Optinose right/left: 2.55/2.75 and 1.18/1.18 cm², respectively, versus a 'normative' mean (range) of 0.85 cm² (0.2-1.6 cm²). Intranasal volumes differed (computed tomography/water fill): Koken, 35.8/38.6 cm³ and Optinose, 24.1/25.0 cm³, versus a 'normative' mean (range) of 26.4 cm³ (20.9-31.1 cm³). <b>Conclusion:</b> Koken cast dimensions are larger than the normal range and the Optinose cast. The validity of casts for regulatory drug deposition studies is suspect.