Formulation and Release Characteristics of Zidovudine-Loaded Solidified Lipid Microparticles

Purpose: To formulate and determine the release profile of zidovudine (AZT)-loaded solidified lipid microparticles (SLMs).Methods: Different concentrations (0, 1, 2, 3 and 5 %w/w) of zidovudine (AZT) were formulated into microparticles in melt dispersion of Phospholipon® 90H and goat fat in the ratio 1:1, 2:1, 2:3 and 1:3 followed by lyophilization. They were characterized for particle size, yield, entrapment efficiency (EE) and loading capacity (LC). In vitro release kinetics and mechanism of release were assessed sequentially in simulated gastric fluid (SGF, pH 1.2)and simulated intestinal fluid (SIF, pH 7.2).Results: The ratio 1: 1 formulation was the most stable in terms of physical observation.. Particle size analysis indicated that the particles were irregular in shape with size ranging from 5.10 ± 0.10 to 13.40 ± 2.20 μm. Yield decreased with increase in drug concentrations in the SLMs formulations. EE data showed that the microparticles containing 1 % w/w of AZT had the highest entrapment efficiency of 74.0 ± 0.03 %. LC also decreased with increase in concentration of AZT. AZT tablet released most of its content within 5 min with a sharp decrease in the concentration but the SLMs maintained its release for 8 to 12 h in different batchesConclusion: The results show that drug content has influence on drug release from the SLMs, but not on the mechanism of release. Furthermore, dose dumping was avoided and drug release mechanism was mostly non-Fickian while for the reference (commercial) tablet, it was Fickian.Keywords: Phospholipon® 90H, Solidified lipid microparticles, Solidified reverse micellar microparticle, Zidovudine

Evaluation of Gentamicin-Entrapped Solid Lipid Microparticles Formulated with a Biodegradable Homolipid from Capra hircus

Purpose: To formulate solidified reverse micellar solutions (SRMS)-based solid lipid microparticles (SLMs) using homolipid from Capra hircus, and evaluate its suitability for the delivery of gentamicin.Methods: SLMs were formulated by melt-emulsification using SRMS (15 % w/w Phospholipon® 90G in 35 % w/w Capra hircus), PEG 4000 and  gentamicin (1.0, 2.0 and 3.0 % w/w), and characterized with respect to size, morphology, encapsulation efficiency (EE) and pH-dependent stability. In vitro release of gentamicin from the SLMs was performed in phosphate buffer (pH 7.4) while bioevaluation was carried out using clinical isolates of Pseudomonas aeruginosa and Staphylococcus aureus.Results: Stable and discrete SLMs of size range 1.47 ± 0.02 to 3.55 ± 0.09 µm were obtained. The SLMs showed a biphasic pattern of drug release and exhibited time-dependent and capacity-limited bioactivity. Overall, SLMs containing 2 % w/w SRMS, 3 % w/w gentamicin and PEG 4000 entrappedthe highest amount of drug, released 99 % of drug and gave the highest inhibitory zone diameter (IZD) against the organisms within 420 min, while plain gentamicin gave the least.Conclusion: SRMS-based SLMs prepared with homolipid from Capra hircus offers a suitable delivery system for gentamicin.Keywords: Solid lipid microparticles, Gentamicin, Capra hircus,   Phospholipon® 90 G, Solidified reverse micellar solutio