Reboxetine

Reboxetine is an antidepressant drug used in the treatment of clinical depression, panic disorder and ADD/ADHD. Its mesilate (i.e. methanesulfonate) salt is sold under tradenames including Edronax®, Norebox®, Prolift®, Solvex® or Vestra®. Reboxetine has two chiral centers, but it only exists as two enantiomers, (R,R)-(-)- and (S,S)-(+)-reboxetine.

Mode of action
Unlike most antidepressants on the market, reboxetine is a norepinephrine reuptake inhibitor (NRI); it does not inhibit the reuptake of serotonin, therefore it can be safely combined with an SSRI.

Side effects
Common side effects of reboxetine include: dry mouth, constipation, headache, drowsiness, dizziness, excessive sweating and insomnia. Hypertension has been infrequently seen.

In 4 to 8% of all patients treated the medication has to be discontinued due to following reasons (percentages represent mean values):
 * insomnia 1.3%
 * excessive sweating 1.1%
 * vertigo/hypotension and paraesthesia 0.8%
 * dizziness, impotence, and other urological problems 0.5% each

Some other rare side effects include anxiety, loss of appetite, urinary retention in men, pain on ejaculation, increased orgasm intensity, and premature/quickened ejaculation.

Reboxetine is very well tolerated. So far no attributable fatalities have been noted. However, it is known to induce a massive mania in those with bipolar disorder.

Metabolism
Both the (R,R)-(-) and (S,S)-(+)-enantiomers of reboxetine are predominantly metabolized by the CYP3A4 isoenzyme. The primary metabolite of reboxetine is O-desethylreboxetine, and there are also three minor metabolites&mdash;Phenol A, Phenol B, and UK1, Phenol B being the most minor.

Interactions with other medications
Because of its reliance on CYP3A4, reboxetine O-desethylation is markedly inhibited by papaverine and ketoconazole.

According to Weiss et al, reboxetine is an intermediate-level inhibitor of P-glycoprotein, which gives it the potential to interact with ciclosporin, tacrolimus, paroxetine, sertraline, quinidine, fluoxetine, fluvoxamine. It has also been known to interact with the analgesic codeine.

The sedative properties of Lorazepam can be increased because Reboxetine interferes with its excretion.

History
By mid-2001, reboxetine was licensed worldwide in over 50 countries, including Italy, Germany and the United Kingdom. In May 2001, however, the Food and Drug Administration declined Pharmacia's license application for the American market. As such it is yet to be available in the United States.