methylcellulose and sibutramine

Obesity is a major chronic health problem in adults. It is a complex, multifactorial disorder characterised by excess accumulation of adipose tissue. It is associated with a number of complications including cardiovascular disease, hypertension, type 2 diabetes, dyslipidaemia and cancer. A weight loss in the order of 5-10% is associated with clinically meaningful reductions with respect to all comorbidities. Diet and exercise has been the cornerstone of weight management therapy, but this approach has limitations, especially for weight maintenance. Previous drugs used in obesity had serious side effects including valvular heart disease. However, recent drugs like orlistat and sibutramine have been rigorously tested and proven safe. Orlistat, a lipase inhibitor, inhibits absorption of dietary fat by approximately 30%. Taken with a hypocaloric diet, it produces and maintains clinically meaningful weight loss. Sibutramine is a centrally-acting agent which enhances satiety and thermogenesis by inhibiting serotonin and noradrenaline re-uptake. It is appropriate for patients who are unable to lose weight by lifestyle modification.

Topics: Anti-Obesity Agents; Appetite Depressants; Clinical Trials as Topic; Cyclobutanes; Humans; Lactones; Methylcellulose; Obesity; Orlistat; Phentermine

To develop a novel sibutramine base-loaded solid dispersion with enhanced solubility and bioavailability, various solid dispersions were prepared using a spray drying technique with hydrophilic polymers such as gelatin, HPMC and citric acid. Their solubility, thermal characteristics and crystallinity were investigated. The dissolution and pharmacokinetics of the sibutramine base-loaded solid dispersion were then compared with a sibutramine hydrochloride monohydrate-loaded commercial product (Reductil). The solid dispersions prepared with gelatin gave higher drug solubility than those prepared without gelatin, irrespective of the amount of polymer. The sibutramine base-loaded solid dispersions containing hydrophilic polymer and citric acid showed higher drug solubility compared to sibutramine base and sibutramine hydrochloride monohydrate. Among the formulations tested, the solid dispersion composed of sibutramine base/gelatin/HPMC/citric acid at the weight ratio of 1/0.8/0.2/0.5 gave the highest solubility of 5.03+/-0.24 mg/ml. Our DSC and powder X-ray diffraction results showed that the drug was present in an altered amorphous form in this solid dispersion. The difference factor (f(1)) values between solid dispersion and commercial product were 2.82, 6.65 and 6.31 at pH 1.2, 4.0 and 6.8, respectively. Furthermore, they had the similarity factor (f(2)) value of 65.68, 53.43 and 58.97 at pH 1.2, 4.0 and 6.8, respectively. Our results suggested that the solid dispersion and commercial product produced a similar correlation of dissolution profiles at all pH ranges. The AUC, C(max) and T(max) of the parent drug and metabolite I and II from the solid dispersion were not significantly different from those of the commercial product, suggesting that the solid dispersion might be bioequivalent to the commercial product in beagle dogs. Thus, the sibutramine base-loaded solid dispersion prepared with gelatin, HPMC and citric acid is a promising candidate for improving the solubility and bioavailability of the poorly water-soluble sibutramine base.

Topics: Animals; Anti-Obesity Agents; Area Under Curve; Biological Availability; Chemical Phenomena; Cyclobutanes; Desiccation; Dogs; Drug Carriers; Gelatin; Hypromellose Derivatives; Male; Methylcellulose; Polymers; Powders; Solubility