Ativan is a member of the benzodiazepine family, similar in compound somewhat to Xanax (alprazolam) and Valium (diazepam) and will have mild sedative effects in that dosage for approx. 6-8 hours. I find this family of prescription medicines a terrific aid in reducing stress and also as a sleep inducing agent on long flights without the grogginess that can result from getting <6 hours sleep on 5 mg. of Ambien or 8 hours on 10mg. I generally take my dosage just before boarding and find that it takes effect in about 30 minutes. If you're intereted in more of the effects from this family of drugs, do a google search and you'll find plenty of additional information (after wading through the links to offshore drug suppliers!) Hope that helps, happy flying!