Formulation and Characterization of Modified Release Microspheres of Lornoxicam Using Okra Gum as Natural Polymer and Ethyl Cellulose as Synthetic Polymer

Objective: The nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely used medications in the world because of their demonstrated efficacy in reducing pain and inflammation. The arthritis, pain and inflammation are effectively treated with Lornoxicam, an effective NSAIDs. Because the drug is weakly acidic, it is absorbed easily in the GI tract, and has a short biological half-life of 3 to 5 hours. To meet the objectives of this investigation, we developed a modified release dosage form to provide the delivery of lornoxicam at sustained rate which was designed to prolong its efficacy, reduce dosage frequency, and enhance patient compliance. The present research work was focused on the development of lornoxicam microspheres using natural polymer like okra gum extracted from the pods of Abelmoschus esculentus Linn. and synthetic polymer like ethyl cellulose along with sodium alginate prepared by Ca2+ induced ionic-gelation cross-linking in a complete aqueous environment were successfully formulated.

Materials and Method: The microspheres were prepared by using sodium alginate with natural polymer (okra gum) and synthetic polymer (ethyl cellulose) in different ratios by Ca2+ induced ionic-gelation cross-linking. The formulations were optimized on the basis of drug release up to 12 hrs. The physicochemical characteristics of Lornoxicam microspheres such as drug polymer interaction study by Fourier Transform Infrared (FTIR) and further confirmation by Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD). The formulated microspheres were characterized for particle size, percentage drug entrapment efficiency, micromeritic properties, surface morphology, percentage swelling index, in-vitro drug release study and mechanism of drug release.

Results and Discussion: The FTIR Spectra revealed that there was no interaction between polymer and Lornoxicam which was further confirmed by DSC and XRD. All the formulated Lornoxicam microspheres were spherical in shape confirmed by SEM. The microspheres exhibited good flow properties and also showed high percentage drug entrapment efficiency. All the batches have excellent flow properties with angle of repose in the range of 25.38° ± 0.04 to 30.41° ± 0.07, carr’s index and hausner’s ratios in the range of 10.40% ± 0.018 to 16.66% ± 0.012 and 1.128 ± 0.09 to 2.225 ± 0.01, respectively. The optical microscopic studies revealed that the mean particle size of all the formulations were found in the range of 819.46 ± 0.07 to 959.88 ± 0.02 μm and percentage of drug entrapment were found to be between 72.35 ± 0.02 to 90.00 ± 0.05. Swelling index of prepared microspheres revealed that with increasing the polymer ratios, there were increase in the swelling of prepared microspheres, showing in the range of 600.76 ± 0.42 to 690.11 ± 0.03% for okra gum microspheres at the end of 9 hr in comparison with ethyl cellulose microspheres which ranges between 179.71 ± 0.07 to 227.73 ± 0.05% at the end of 7 hr. In-vitro drug release of prepared microspheres formulation code LSO4 and LSE4 were found to be 88.654 ± 0.25% and 93.971 ± 0.20% respectively at the end of 12 hr. It was suggested that increase in polymer concentration, the drug release from the prepared microspheres got retarded producing sustained release of lornoxicam. In-vitro drug release data obtained were fitted to various release kinetic models to access the suitable mechanism of drug release. Drug release from lornoxicam-loaded alginate-okra gum microspheres followed a pattern that resembled sustained release (Korsemeyer-Peppas model) (R2 = 0.9925 to 0.9951), and n ≤ 1 indicated anomalous diffusion (non-Fickian), supercase-II transport mechanism LSO4 (n = 1.039) over a period of 12 hour underlying in-vitro drug release. Moreover, zero order model (R2 = 0.9720 to 0.9949) were found closer to the best-fit Korsemeyer - Peppas model.

In addition, the drug release from lornoxicam-loaded alginate-ethyl cellulose microspheres also follow Korsemeyer-Peppas model (R2 = 0.9741 to 0.9973) with near to Hixson-Crowell model (R2 = 0.9953 to 0.9985) and n < 1 indicated non-Fickian diffusion or anomalous transport mechanism. Moreover, first order model with non-Fickian diffusion mechanism (R2 = 0.9788 to 0.9918) were found closer to the best-fit Korsemeyer-Peppas model/ Hixson-Crowell model.

Conclusion: The present study conclusively demonstrates the feasibility of effectively encapsulating Lornoxicam into natural polymer (okra gum) and synthetic polymer (ethyl cellulose) to form potential sustained drug delivery system. In conclusion, drug release over a period of 12 hrs, could be achieved from these prepared microspheres. A pH-dependent swelling and degradation of the optimized microspheres were also observed, which indicates that these microspheres could potentially be used for intestinal drug delivery.