slippahs is right on the money! Try 'em at home first, be sure you consult with your health practitioner - not every medication is for every one - and check the effects very carefully. At least one medication some flyers use has anterograde amnesia as a side effect; make an unscheduled early landing, e.g. Gander instead of London, and you may not be compos mentis. And be very, very cautious about mixing most of these with alcohol - they are often potentiated by alcohol, so rather than a "1+1 = 2" you may have a "1+1=8" effect.

OTOH, there are IMO alternative, better and more natural ways to deal with flying and jet lag that are entirely natural, using your diet and preparation. The most notable is probably the "jet lag" diet developed for the Argonne National Laboratory by Dr. Charles Ehret, which has been used by military and global diplomatic workers. I use a modified Argonne diet and do not use any medication; in the military, I used to be on global two hour alert - from the US West Coast, we could be on our way to anywhere in the world within two hours, and had to be fully functional on arrival; we were only called out when the local folks could not handle a critical issue.

I can easily acclimate myself to local time (e.g. SFO-LHR-JNB, with the diet and getting as much natural light in the afternoon, hitting bed at 9 - 10 PM I awake at my normal hour of 6 AM and am ready to go.) Basically, using the Argonne / Ehret diet you use your body's natural biochemical and photochemical cycles to work for you, not against you, when you cross several time zones.

They will calculate the diet for you or you can use the link that says "Free - How to do it yourself." I find I don't have to be too exact in the application of this diet, but merely follow the main ideas.