Molecule

Drug Groups

illicit; approved; withdrawn; investigational

Description

Sibutramine (trade name Meridia in the USA, Reductil in Europe and other countries), usually as sibutramide hydrochloride monohydrate, is an orally administered agent for the treatment of obesity. It is a centrally acting stimulant chemically related to amphetamines. Sibutramine is classified as a Schedule IV controlled substance in the United States. In October 2010, Sibutramine was withdrawn from Canadian and U.S. markets due to concerns that the drug increases the risk of heart attack and stroke in patients with a history of heart disease.

Indication

For the treatment of obesity.

Pharmacology

Sibutramine is an orally administered agent for the treatment of obesity. 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 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. 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-HT_1A, 5-HT_1B, 5-HT_2A, 5-HT_2C), norepinephrine (b, b1, b3, a1 and a2), dopamine (D1 and D2), benzodiazepine, and glutamate (NMDA) receptors. These compounds also lack monoamine oxidase inhibitory activity in vitro and in vivo.

Toxicity

Side effects include dry mouth, anorexia, insomnia, constipation and headache.

Affected Organisms

Biotransformation

Hepatic

Absorption

Rapid absorption following oral administration. Absolute bioavailability is not known, but at least 77% of a single oral dose of sibutramine is absorbed.

Half Life

1.1 hours

Protein Binding

97% (to human plasma proteins)

Elimination

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. 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. The primary route of excretion for M1 and M2 is hepatic metabolism and for M5 and M6 is renal excretion.

Clearance

* Oral cl=1750 L/h [oral administration]

References

External Links