CHina Sibutramine powder

CHina Sibutramine powder

(sibutramine hydrochloride monohydrate) is an orally administered agent for the treatment of obesity. Chemically, the active ingredient is a racemic mixture of the (+) and (-) enantiomers of cyclobutanemethanamine, 1-(4-chlorophenyl)-N,N-dimethyl-α­ (2-methylpropyl)-, hydrochloride, monohydrate, and has an empirical formula of C17H29Cl2NO. Its molecular weight is 334.33. The structural formula is shown below:

Sibutramine hydrochloride monohydrate is a white to cream crystalline powder with a solubility of 2.9 mg/mL in pH 5.2 water. Its octanol: water partition coefficient is 30.9 at pH 5.0. Each MERIDIA capsule contains 5 mg, 10 mg, and 15 mg of sibutramine hydrochloride monohydrate. It also contains as inactive ingredients: lactose monohydrate, NF; microcrystalline cellulose, NF; colloidal silicon dioxide, NF; and magnesium stearate, NF in a hard-gelatin capsule [which contains titanium dioxide, USP; gelatin; FD&C Blue No. 2 (5- and 10-mg capsules only); D&C Yellow No. 10 (5- and 15-mg capsules only), and other inactive ingredients].

Mode of Action Sibutramine produces its therapeutic effects by norepinephrine, serotonin and dopamine reuptake inhibition. Sibutramine and its major pharmacologically active metabolites (M1 and M2) do not act via release of monoamines. Pharmacodynamics Sibutramine exerts its pharmacological actions predominantly via its secondary (M1) and primary (M2) amine metabolites. The parent compound, sibutramine, is a potent inhibitor of serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine reuptake in vivo, but not in vitro. However, metabolites M1 and M2 inhibit the reuptake of these neurotransmitters both in vitro and in vivo. In human brain tissue, M1 and M2 also inhibit dopamine reuptake in vitro, but with ~3-fold lower potency than for the reuptake inhibition of serotonin or norepinephrine.

CHina Sibutramine powder

Sibutramine and its metabolites (M1 and M2) are not serotonin, norepinephrine or dopamine releasing agents. Following chronic administration of sibutramine to rats, no depletion of brain monoamines has been observed. Sibutramine, M1 and M2 exhibit no evidence of anticholinergic or antihistaminergic actions. In addition, receptor binding profiles show that sibutramine, M1 and M2 have low affinity for serotonin (5-HT1, 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2C), norepinephrine (β, β1, β3, α1 and α2), dopamine (D1 and D2), benzodiazepine, and glutamate (NMDA) receptors. These compounds also lack monoamine oxidase inhibitory activity in vitro and in vivo.

CHina Sibutramine powder

Absorption Sibutramine is rapidly absorbed from the GI tract (Tmax of 1.2 hours) following oral administration and undergoes extensive firstpass metabolism in the liver (oral clearance of 1750 L/h and half-life of 1.1 h) to form the pharmacologically active mono- and didesmethyl metabolites M1 and M2. Peak plasma concentrations of M1 and M2 are reached within 3 to 4 hours. On the basis of mass balance studies, on average, at least 77% of a single oral dose of sibutramine is absorbed. The absolute bioavailability of sibutramine has not been determined. Distribution Radiolabeled studies in animals indicated rapid and extensive distribution into tissues: highest concentrations of radiolabeled material were found in the eliminating organs, liver and kidney. In vitro, sibutramine, M1 and M2 are extensively bound (97%, 94% and 94%, respectively) to human plasma proteins at plasma concentrations seen following therapeutic doses. Metabolism Sibutramine is metabolized in the liver principally by the cytochrome P450 (3A4) isoenzyme, to desmethyl metabolites, M1 and M2. These active metabolites are further metabolized by hydroxylation and conjugation to pharmacologically inactive metabolites, M5 and M6. Following oral administration of radiolabeled sibutramine, essentially all of the peak radiolabeled material in plasma was accounted for by unchanged sibutramine (3%), M1 (6%), M2 (12%), M5 (52%), and M6 (27%). M1 and M2 plasma concentrations reached steady-state within four days of dosing and were approximately two-fold higher than following a single dose. The elimination half-lives of M1 and M2, 14 and 16 hours, respectively, were unchanged following repeated dosing. Excretion Approximately 85% (range 68-95%) of a single orally administered radiolabeled dose was excreted in urine and feces over a 15-day collection period with the majority of the dose (77%) excreted in the urine. Major metabolites in urine were M5 and M6; unchanged sibutramine, M1, and M2 were not detected. The primary route of excretion for M1 and M2 is hepatic metabolism and for M5 and M6 is renal excretion.