Metoprolol Succinate Microspheres: Influence of Pectins Obtained from the Peels of Lemon (Citrus limon) and Orange (Citrus sinensis) Fruits as Controlled Release Polymers

Drug-release characteristics of microspheres can be influenced by the type of coating material used in the formulation. The peels of the citrus fruits, Lemon (Citrus limon) and Orange (Citrus sinensis) Family Rutaceae, are sources of pectins, and these were evaluated as sustained release polymers in the formulation of microspheres of metoprolol succinate (MS), an antihypertensive agent. Lemon and Orange pectins were characterized using morphology, Fourier Transform Infra-red (FTIR) analysis, qualitative and quantitative tests. Metoprolol succinate microspheres were prepared by ionic gelation using each pectin, co-blended with sodium alginate. The microspheres were characterized using Scanning Electron Microscope (SEM), FTIR analysis, drug entrapment and quantity of drug released in 12 hours (Q12). The 23 full factorial design was applied to evaluate the individual and interactive effects of three variables: X1, pectin:alginate ratio, X2, Polymer: drug ratio, and X3, type of pectin in polymer blend on size, swelling, drug entrapment and Q12. Yields of pectin from Orange and Lemon were 16.40 and 18.24%, respectively with methoxy content of 4.30 and 5.20%. Spherical microspheres with drug entrapment of 57.71 ± 8.96 to 90.72 ± 9.21% and Q12 of 7.40 to 12.50% were obtained. The FTIR spectra suggested that there were no interactions between metoprolol and polymers. The swelling, entrapment and dissolution time increased with increase in pectin content. The factor X2 had the most influence on microsphere properties while the interactive effects of X2X3 had the most influence. Optimization of the analyzed responses demonstrated that peak conditions for obtaining desired maximum properties was by using Orange pectin at pectin: alginate and polymer: drug ratios of 2:1. Lemon and Orange pectins showed potential as cheaper alternative polymers in sustaining the release of metoprolol succinate from microspheres.