Investigation of injectable drospirenone organogels with regard to their rheology and comparison to non-stabilized oil-based drospirenone suspensions

Abstract

The objective of this study was to evaluate organogels as potential injectable drug-delivery systems for drospirenone (DRSP). Recently, studies on organogel characterization with focus on the parenteral injection are rarely to find in the literature. DRSP organogels contained the drug suspended in medium-chain triglycerides and were stabilized by various organogelators. The DRSP organogels were assessed in comparison to non-stabilized DRSP microcrystal suspensions (MCSs). Furthermore, rheological properties of the organogels, in particular the elastic modulus (G′), the complex viscosity (η*) and the elasticity, were evaluated with respect to the long-term stability, syringeability/injectability and in vitro release. DRSP organogels showed significantly improved storage stability compared to non-stabilized MCSs with regard to sedimentation and particle growth. Furthermore, all of the DRSP organogels showed shear-thinning behavior. Thus, ejection from syringes was possible by an autoinjector using 23G needles comparable to non-stabilized MCSs. Nevertheless, DRSP organogels exhibited significantly more sustained drug release than non-stabilized MCSs most likely caused by partial recovery of the organogelator structures at 37 °C after destruction. Consequently, DRSP organogels were evaluated to be superior to conventional non-stabilized MCSs. Silica organogels, which provided the highest elasticity, moderate G' and η* and avoided most efficiently particle growth, are slightly more preferable compared to the other DRSP organogels.

• Gel
• long-term stability
• particle size
• sedimentation
• silica
• steroid
• suspension
• viscosity

Acknowledgements

We thank Sven Wegner and the Department of Analytical Development Physical Chemistry, Intendis, as well as the Department of Pharmaceutical Technology Packaging Development for the opportunity to accomplish the experiments and for the technical assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

S. N. was supported by a PhD scholarship of Bayer HealthCare Pharmaceuticals.