Orexin-blocking pill speeds sleep onset.

A new compound that inhibits the activity of alertness-promoting brain peptides called orexins shows promise as a sleeping pill, according to tests in people and animals.

Men who took the drug fell asleep more quickly than did men who took a placebo, neurobiologist Francois Jenck of Actelion Pharmaceuticals in Allschwil, Switzerland, and his collaborators report in the February Nature Medicine.

Larger doses of the drug act faster and seem to have a stronger effect than do smaller doses, the researchers found. They previously observed similar effects in both dogs and rats.

The duration of drug-induced somnolence also depends on dose. The highest dose used in people caused drowsiness that lasted about 10 hours, the researchers report.

The drug, now known as ACT-078573, harnesses the 8-year-old discovery that insufficient orexin activity in the brain causes narcolepsy, a disorder of excessive sleepiness (SN: 8/14/99, p. 100). Researchers have since theorized that an orexin-blocking drug might overcome insomnia.

Narcoleptic people experience sudden bouts of muscle weakness, called cataplexy. Jenck's team found no signs of cataplexy as a side effect of the drug.--B.H