Pregnancy Category C

Uses. This substance is a sleep inducer that also has anticonvulsant properties. Zaleplon is neither an opiate nor a barbiturate nor a benzodiazepine depressant.

The drug's sleep-inducing effects wear off so quickly that zaleplon seems suitable for use in the middle of the night without risk of hangover drowsiness after waking up. The substance has been approved for NASA (National Aeronautics and Space Administration) space shuttle crews and has been carried on flights, an environment where immediate alertness is required upon awakening. Despite lack of grogginess after people rouse themselves, they should nonetheless avoid dangerous activity (such as driving a car) right after taking a drug intended to induce sleep. Researchers testing zaleplon when it was active, rather than after its effects should have worn off, found that it interfered with people's actions to about the same extent as triazolam but less than lorazepam or Zolpidem. Sleep medicines with short action sometimes make people nervous after extended use, and nervousness has been reported by some persons using zaleplon, but that unwanted effect was not observed in formal tests with the drug. Experiments with rats and mice find zaleplon to have an antianxiety property. Results of human research conflict on whether zaleplon has a brief rebound insomnia effect, but the trend is to find no rebound. "Rebound" is when people have trouble sleeping for a night or two after dosage stops.

One study found doses to be more potent among Japanese than among Americans. The reason is unclear; it may be related to average body weights or to some ethnic factor.

Drawbacks. Zaleplon can cause people to forget what happens for a couple of hours after a dose, and some persons still have amnesia trouble the day after a dose. One experiment found the intensity of that effect to be compa-

rable to lorazepam's but shorter in duration. Because of possible memory difficulty, an individual using zaleplon may want to avoid situations involving important decisions. Other unwanted effects may include skin rash, muscle tightness, pain in chest and back, migraine headache, constipation, difficulty in concentrating, and emotional depression. Euphoria is a less common effect.

Abuse factors. Studies indicate zaleplon has about the same potential for abuse as benzodiazepine class depressants do. Researchers using volunteers who had previously abused drugs concluded that zaleplon and triazolam have the same abuse potential. No tolerance emerged in studies where people took zaleplon for weeks and months. No dependence developed either, but that finding is not considered conclusive. In animal studies dependence has occurred, severe enough that some animals died when the drug was cut off. Researchers conducting a baboon experiment found zaleplon to have about the same dependence potential as triazolam.

Drug interactions. Alcohol should be avoided when taking zaleplon. Tests have demonstrated that zaleplon boosts the effects of alcohol and also boosts some action of the psychiatric medication thioridazine.

Cancer. Cancer emerged in some mice that received 6 to 49 times the maximum human dose of zaleplon for two years, but cancer did not develop in rats that received 5 to 10 times the maximum human dose. Likewise, laboratory tests of the drug's cancer-causing potential have had mixed results.

Pregnancy. The drug has not caused birth defects in rats and rabbits receiving almost 50 times the maximum human dose. Rat offspring had impaired growth, however. The drug passes into maternal milk of rats at levels high enough to affect offspring; keep in mind, however, that these milk levels result from doses exceeding the maximum recommended for humans. In humans the drug passes into milk of nursing mothers; impact on the infants is unknown but is presumed to be harmless. At its peak the amount of zaleplon in milk is less than 0.02% (two one-hundredths of one percent) of the mother's dose, and that amount declines rapidly an hour after a mother takes zaleplon.

Additional information. Sonata tablets contain FD&C Yellow No. 5 (tartra-zine), to which some persons seem allergic, particularly if they have an aspirin sensitivity.

Additional scientific information may be found in:

Chagan, L., and L.A. Cicero. "Zaleplon: Possible Advance in the Treatment of Insomnia." P&T: A Peer-Reviewed Journal for Formulary Management 24 (1999): 590. Heydorn, W.E. "Zaleplon—A Review of a Novel Sedative Hypnotic Used in the Treatment of Insomnia." Expert Opinion on Investigational Drugs 9 (2000): 841-58. Mangano, R.M. "Efficacy and Safety of Zaleplon at Peak Plasma Levels." International

Journal of Clinical Practice: Supplement 79, no. 116 (2001): 9-13. Rush, C.R., J.M. Frey, and R.R. Griffiths. "Zaleplon and Triazolam in Humans: Acute Behavioral Effects and Abuse Potential." Psychopharmacology 145 (1999): 39-51. Troy, S., and M. Darwish. "Maximal Effects and Residual Effects: Zaleplon vs. Zolpidem and Triazolam." American Society of Hospital Pharmacists Annual Meeting 56 (June 1999): 59.

Troy, S., et al. "Comparison of the Effects of Zaleplon, Zolpidem, and Triazolam on Memory, Learning, and Psychomotor Performance." Journal of Clinical Psycho-pharmacology 20 (2000): 328-37. "Zaleplon for Insomnia." Medical Letter on Drugs and Therapeutics 41 (1999): 93-94.

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