Preparation and in-vitro evaluation of sustained release theophylline micro-spheres

A modified emulsion-solvent evaporation technique was utilized to prepare sustained release microspheres containing theophylline [TH]. Two polymers were used for microspheres preparation, namely cellulose propionate [CP] and ethyl cellulose [EC]. The two polymers were used at 1:1, 2:1, and 3:2 [drug - polymer ratios]. The prepared microspheres were evaluated for their total recovery, drug loading, particle size distribution, surface morphology, drug content and drug release rate characteristics. The results have shown that, the total percentages drug recovery reached 96, 97.7and 90.3 for cellulose propionate at 1:1, 2:1 and 3:2 [drug -polymer ratios], and that of drug loading reached 89, 90, and 92 respectively. However, with ethyl cellulose, the total% drug recovery reached 99, 100, and 94 using the same drug -polymer ratios, and the total% drug loading reached, 85, 90, and 90 respectively. The results obtained have shown a significant complete recovery with an excellent drug loading and thus the efficiency of the procedure utilized to encapsulate the drug. The drug release characteristics from the prepared microspheres in simulated gastric fluid [pH 1.2] and phosphate buffer [pH 6.8] were compared with commercial sustained release capsules of theophylline [Theo SR 100]. Results have revealed that, the release rate of theophylline was influenced by the type of polymer, microsphere size, pH as well as drug to polymer ratio. The decrease in particle size of the prepared microspheres led to increase in the release rate. However, the prepared microspheres showed more retarded release of theophylline than from the tested commercial product. Moreover, ethyl cellulose as a polymer was more effective for sustained effect. The release data were fitted to Peppas diffusion equation. Results have indicated that the release pattern of theophylline followed zero-order kinetics

Formulation and stability of ciprofloxacin hydrochloride ophthalmic eye drops

Ciprofloxacin hydrochloride [CPX-HCL] ophthalmic solutions were formulated using different, polymers, buffers and antioxidants. The polymer solutions tested were sodium carboxy methylcellulose [SCMC] 0.1%, hydroxypropyl methylcellulose [HPMC] 2%, methylcellulose 400 [MC] 0.6%, polyethylene glycol 6000 [PEG] 10%, polyvinyl alcohol [PVA] 2% and polyvinylpyrrolidone K25 [PVP] 10%. [CPX-HCL] gave clear solutions with only [MC] and [HPMC] at the same pH range of other tested polymers. Also, the acetate buffer [pH 4.8] was the only suitable buffer for forming a stable ophthalmic solution. The results also revealed that 0.05% is the optimum EDTA concentration as antioxidant. Consequently, the eye drops were prepared with 0.6% MC and 2% HPMC in distilled water or in presence of acetate buffer [pH 4.8]. Benzalkonium chloride [0.004%] was added in all formulae and the isotonicity was adjusted by sodium chloride. The stability of the four formulae was investigated for 24 months at different temperatures [4C, 37C and 45C]. The drug showed greater stability in acetate buffer than in double distilled water. The formula prepared with HPMC in acetate buffer exhibited the highest stability at all tested temperatures. This formula showed reduction in drug potency by 94.69, 91.09 and 86.01% after storage for two years at 4C, 37C and 45C, respectively. All formulae showed reduction in drug potency to about 85% of its initial potency after storage for 14 days in presence of light at room temperature. The low density high density polyethylene plastic containers and amber colored glass showed insignificant difference on drug stability