Encapsulating Rifampicin into SLNs: A Viable Option for Managing its Bioavailability Issues Upon Co-Delivery with Isoniazid

Background: Rifampicin is known to degrade at the acidic pH of the stomach, especially in the presence of isoniazid. Although isoniazid also degrades partially, its degradation is reversible. Objective: Presently, we provide a proof of the fact that the simultaneous oral administration of rifampicin (RIF), upon incorporation into solid lipid nanoparticles (RIF-SLNs), with isoniazid (INH) overcomes its INH-induced degradation and improves its oral bioavailability in rats. Methods: Solid lipid nanoparticles of RIF (RIF-SLNs) were prepared using a novel and patented method. The effect of INH was investigated on in vivo bioavailability of RIF both in its free and encapsulated (RIF-SLNs) form, after oral administration to rats. Results: C_max and AUC_0-∞ of RIF increased 158 % and 125 %, respectively, upon incorporation into SLNs versus free RIF when combined with INH. The T_max decreased from 5.67 h to 3.3 h, and the plasma concentration of RIF remained above its MIC (8 μg/ml) at all the tested time points starting with 15 min, when administered as RIF-SLNs in combination with INH. Conclusion: The results confirm the scope of combining RIF-SLNs with INH to overcome the bioavailability of free RIF when combined with INH, especially in fixed dose combinations.