Development of a long-acting intramuscularly injectable formulation with nanosuspension of andrographolide

In this research, andrographolide (AG) nanosuspension was produced using wet milling method and its pharmacokinetic behavior was evaluated after intramuscular (i.m.) and oral administration. AG nanosuspension was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The crystal structure wasn't damaged by wet milling and no obvious crystal structure change was found between bulk AG and AG nanosuspension. In vitro dissolution showed a higher dissolution rate from AG nanosuspension (85.5%), compared with that of bulk AG (69.1%) at 90 min. Following intramuscularly injection, the release of AG lasted for 4 weeks. The histological examination implied that AG nanosuspension produced very few inflammation responses and gradually returned to normal after 14 d i.m. administration. These results suggested that AG nanosuspension could be developed as a potential delivery system for long-acting intramuscular administration.