From waste to a resource? Hemicelluloses enhance the dissolution and stability of the amorphous state of carbamazepine

Both synthetic and natural polymers are used as excipients in various pharmaceutical prepara-tions. Natural polymers offer advantages, such as abundant availability, cost-effectiveness, non -toxicity, biocompatibility, and biodegradability. Hemicelluloses are highly promising natural polymers for pharmaceutical applications due to their advantageous colloidal properties, but their ability to solubilize poorly water-soluble drugs and stabilize their amorphous form is cur-rently virtually unexplored. In this study, we showed the applicability of birch, spruce and wheat straw hemicelluloses as tablet excipients and their ability to enhance dissolution and stability of a model drug, carbamazepine (CBZ), in amorphous solid dispersions. The hemicelluloses formed sufficiently strong tablets by direct-compression, although addition of CBZ weakened the tablets. The hemicelluloses did not modify drug release from the tablets when compared to plain CBZ powder. Solid dispersions with CBZ were identified as amorphous one-phase mixtures, with hy-drogen bonding between the hemicelluloses and CBZ. The mixtures remained stable for at least nine months under 40 degrees C/23 % RH. Dissolution of the amorphous solid dispersions decreased with increasing hemicellulose molar mass. Up to 7.6-fold CBZ supersaturation was achieved, al-though it did not improve CBZ permeation through a PAMPA (parallel artificial membrane per-meability assay) barrier when compared to the corresponding physical mixtures. In summary, birch, spruce, and wheat straw hemicelluloses formed direct-compressed tablets and stable amor-phous solid dispersions that may improve dissolution properties of drugs. Differences exist be-tween hemicelluloses from different plant sources and thus more research with structurally dif-ferent drug substances is needed in the future.