Chemotherapeutic potential of alginate-chitosan microspheres as anti-tubercular drug carriers

OBJECTIVES: This study was designed to develop alginate-chitosan microspheres as drug carriers to reduce dose/dosing frequency in the management of tuberculosis (TB), which otherwise demands prolonged chemotherapy. METHODS: Alginate-chitosan microspheres encapsulating three frontline anti-tuberculous drugs (ATDs), rifampicin, isoniazid and pyrazinamide, were formulated. A therapeutic dose and a half-therapeutic dose of the microsphere-encapsulated ATDs were orally administered to guinea pigs for pharmacokinetic/chemotherapeutic evaluations, respectively. RESULTS: The drug encapsulation efficiency ranged from 65% to 85% with a loading of 220-280 mg of drug per gram microspheres. Administration of a single oral dose of the microspheres to guinea pigs resulted in sustained drug levels in the plasma for 7 days and in the organs for 9 days. The half-life and mean residence time of the drugs were increased 13- to 15-fold by microsphere encapsulation, along with an enhanced relative/absolute bioavailability. The sustained release and increase in bioavailability were also observed with a sub-therapeutic dose of the microspheres. In Mycobacterium tuberculosis H37Rv-infected guinea pigs, administration of a therapeutic dose of microspheres spaced 10 days apart produced a clearance of bacilli equivalent to conventional treatment for 6 weeks. The most important observation, however, was the documentation of therapeutic benefit with a half-therapeutic dose of the microspheres administered weekly. CONCLUSION: Alginate-chitosan microspheres hold promise as a potential natural polymer-based oral ATD carrier for better management of TB.