Polymorphism of glyceryl behenates: From the individual compounds to the pharmaceutical excipient

• Glyceryl behenates are widely used in pharmaceutical formulations, from solid dosage forms to nanoparticles.
• Solid state behavior of glyceryl behenates result from the presence of the three main constituents: mono, di and tri-behenin.
• The monoglycerides content was shown to be essential to give its final structure to the glyceryl behenates excipient.
• Special attention has to be required when mixing glyceryl behenates with other constituents that could trap monoglycerides.

The present paper deals with the crystallization behavior of glyceryl behenate mixtures that are extensively used in the field of drug delivery. The aim of the study was to understand the structural and thermal behaviors of Compritol® by considering first the individual polymorphism of the main components constituting this excipient and then their mixtures. This excipient mainly contains dibehenin (∼50%), tribehenin (∼30%) and monobehenin (20%). It appeared clearly that the mixture polymorphism did not result from a simple addition of the individual behavior. Indeed, the solid state organization of this excipient strongly depended on the presence of the third main component, monobehenin, into the mixture. Furthermore, a threshold ratio of monobehenin, at least 10%, must be reach in order to obtain the typical structural organization (co-existence of α/sub-α subcells) and thermal behavior (solid–solid transition and melting) of Compritol®. This underlines that special attention is required when mixing Compritol® with other pharmaceutical ingredients that could trap monoglycerides and modify the equilibrium present in the pure excipient.

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