402 Sibutramine
and other medicine). The drug is a “serotonin reuptake inhibitor,” meaning it
can interact with various medicines (includingdextromethorphan,fentanyl,
meperidine, andpentazocine) to cause “serotonin syndrome,” a serious con-
dition that can involve hyperactivity, confusion, and influenzalike symptoms.
Sibutramine should be used cautiously if a person is takingephedrine, con-
tained in some cold and allergy remedies.
Cancer.Mice experiments involving blood plasma levels similar to normal
human dosage found no evidence that sibutramine causes cancer. In experi-
mentation producing levels of sibutramine metabolites (breakdown products)
many times higher than those seen in humans, female rats showed no evi-
dence of cancer; but male rats developed tumors that are commonly caused
by hormone changes. Typical laboratory tests used to measure a chemical’s
cancer potential show none for sibutramine, though its breakdown products
produced ambiguous results in one test.
Pregnancy.Rat studies involving doses strong enough to produce metabo-
lite blood levels 43 times higher than normal human levels yielded no ob-
servable birth defects. Some rabbit studies involving doses high enough to be
poisonous have produced birth defects, but other testing at a poisonous dos-
age level has not. Sibutramine’s potential for causing human congenital ab-
normalities is unknown, and pregnant women are advised to avoid the drug.
Its potential for transfer into milk is unknown, so nursing mothers are advised
to avoid the drug.
Additional information.The hydrochloride anhydrous form of sibutramine
was tested as an antidepressant in the 1980s, but medical literature has re-
ported little about this form of the drug since then. The hydrochloride mon-
ohydrate form became available in the 1990s to help people lose weight.
Additional scientific information may be found in:Cole, J.O., et al. “Sibutramine: A New Weight Loss Agent without Evidence of the
Abuse Potential Associated with Amphetamines.”Journal of Clinical Psychophar-
macology18 (1998): 231–36.
James, W.P., et al. “Effect of Sibutramine on Weight Maintenance after Weight Loss:
A Randomised Trial.”Lancet356 (2000): 2119–25.
Lean, M.E. “Sibutramine—A Review of Clinical Efficacy.”International Journal of Obesity
and Related Metabolic Disorders21 (1997, Suppl. 1): S30–S36.
Luque, C.A., and J.A. Rey. “Sibutramine: A Serotonin-Norepinephrine Reuptake-
Inhibitor for the Treatment of Obesity.”Annals of Pharmacotherapy33 (1999):
968–78.
Schuh, L.M., et al. “Abuse Liability Assessment of Sibutramine, a Novel Weight Control
Agent.”Psychopharmacology147 (2000): 339–46.
“Sibutramine for Obesity.”Medical Letter on Drugs and Therapeutics40 (1998): 32.