A Comparison of Different Anatomical Throats vs The USP Throat

Samantha Holmes, Alex Slowey

3M Drug Delivery Systems Division, Morley Street, Loughborough, Leics, LE11 1EP, UK

Summary

Anatomical throat models, for the purpose of generating aerodynamic particle size distribution (APSD) profiles for inhaled pharmaceutical products, are increasingly available within the inhalation industry. An appreciation of the differences between profiles generated using the standard United States Pharmacopeia (USP) and anatomical throat is necessary in order to ensure that when showing in-vitro equivalence, the use of an anatomical throat is included to facilitate in-vivo prediction.

This paper presents the effect on the level of drug deposition in the throat, impactor sized mass (ISM) and <5μm fine particle mass (FPM_<5µm) when each throat model is employed during testing of a metered dose inhaler (MDI) with the next generation impactor (NGI) at a standard flow rate of 30 L/min.

A comparison of two independent anatomical throat models, developed by Emmace Consulting, (Lund, Sweden) and Nanopharm Ltd, (Newport, U.K.) respectively; demonstrated that for the three parameters considered within this paper, throat deposition, ISM and FPM_<5µm data for each of the cast designs, were comparable.

Differences in the throat deposition, ISM and FPM_<5µm predicted through the use of actuators with multiple exit orifice diameters, were enhanced when testing with the USP throat in contrast to the conclusions drawn from the anatomical throat data.

When assessing in-vitro equivalence, consideration should include an assessment of an anatomical throat in order to more closely predict in-vivo performance.