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Reformulation of Stmerin(®) D CFC formulation using HFA propellants
Saburo Murata1, Takashi Izumi, Hideki Ito
1Pharmaceutical Research and Technology Laboratories, Astellas Pharma Inc. Yaizu, Japan. saburo.murata@astellas.com
Pharmaceutical Development and Technology
|April 24, 2012
Summary
This study successfully reformulated Stmerin® D using hydrofluoroalkanes (HFAs) as propellants, improving drug suspension stability with medium-chain triglycerides (MCT) and optimizing spray performance through actuator adjustments for a viable alternative to CFCs.
Area of Science:
- Pharmaceutical Technology
- Inhalation Drug Delivery
- Materials Science
Background:
- Chlorofluorocarbons (CFCs) are being phased out as metered dose inhaler (MDI) propellants.
- Hydrofluoroalkanes (HFAs) are proposed as environmentally friendly alternatives.
- Reformulating existing CFC-based inhalers to HFAs presents formulation and performance challenges.
Purpose of the Study:
- To evaluate the suspension stability and spray performance of a reformulated Stmerin® D using HFAs (HFA-134a and HFA-227) compared to the original CFC formulation.
- To identify suitable surfactants and co-solvents for improving drug suspension in HFAs.
- To optimize actuator configurations for achieving comparable spray performance to the original CFC-based MDI.
Main Methods:
- Preparation of metered dose inhalers (MDIs) using HFA propellants with various surfactants and co-solvents.
- Visual testing to assess drug suspension stability in different HFA formulations.
- Cascade impaction studies to evaluate spray performance, including fine particle dose (FPD).
- Modification of actuator orifice diameter and cone angle to control spray characteristics.
Main Results:
- Drug suspension stability was initially poor in both HFA-134a and HFA-227 formulations.
- Addition of medium-chain triglycerides (MCT) significantly improved suspension stability, especially with HFA-227.
- The higher vapor pressure of HFA-227 led to an increased fine particle dose (FPD).
- Spray performance was successfully controlled by altering actuator configuration, with a 0.8 mm orifice and 90° cone angle yielding results comparable to the original CFC formulation.
Conclusions:
- Reformulation of Stmerin® D using HFA-227 is feasible.
- Medium-chain triglycerides (MCT) are effective suspending agents for HFA-based inhaler formulations.
- Actuator design is a critical factor in achieving desired spray performance for HFA MDIs, enabling a successful transition from CFCs.
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