Related Experiment Video
Updated: Feb 25, 2026

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles
Published on: January 7, 2019
USP Apparatus 4: a Valuable In Vitro Tool to Enable Formulation Development of Long-Acting Parenteral (LAP)
William P Forrest1, Kevin G Reuter2, Vivek Shah2
1Analytical Sciences, MRL, Merck & Co., Inc., Rahway, New Jersey, 07065, USA. william.forrest@merck.com.
Abstract:
Long-acting or extended release parenteral dosage forms have attracted extensive attention due to their ability to maintain therapeutic drug concentrations over long periods of time and reduce administration frequency, thus improving patient compliance. It is essential to have an in vitro release (IVR) testing method that can be used to assure product quality during routine production as well as predict and understand the in vivo performance of a formulation. The purpose of this work was to develop a discriminatory in vitro release method to guide formulation and process development of long-acting parenteral (LAP) nanosuspension formulations composed of poorly water-soluble drugs (BCS class II). Injectable nanosuspension formulations were developed to serve as test articles for method development. Several different IVR methods were evaluated for their application to the formulation screening and process development including (1) USP apparatus 2, (2) dialysis and reverse dialysis sac, and (3) continuous flow-through cell (USP apparatus 4). Preliminary data shows the promising results to support the utilization of USP 4 over more widely accepted USP 2 and dialysis methods. A combination of more representative in vivo hydrodynamics and ease of maintaining sink conditions yields the USP 4 flow-through cell method a more suitable in vitro release method for nanosuspension-based LAP formulations of poorly water-soluble compounds, such as compounds A and B.
More Related Videos
Related Concept Videos
In Vitro Drug Dissolution: Compendial Testing Models I
In Vitro Drug Dissolution: Alternative Methods
In Vitro Drug Dissolution: Compendial Testing Models II
Factors Affecting Dissolution: Particle Size and Effective Surface Area
Factors Influencing Drug Absorption: Pharmaceutical Parameters
Parenteral Drug Delivery Systems: Injectables, Implants, and Infusion Devices

