According to an article in the New York Times: http://www.nytimes.com/2008/12/21/world/middleeast/21drugs.html?_r=1&pagewanted=all
Trihexyphenidyl an antimuscarinic typically prescribed for Parkinson's disease can provide one with a sense of "euphoria and well being" when taken in larger doses. There's been a dramatic rise in its abuse with Iraqi soldiers and police.
Dear Drugs-Forum readers: We are a small non-profit that runs one of the most read drug information & addiction help websites in the world. We serve over 4 million readers per month, and have costs like all popular websites: servers, hosting, licenses and software. To protect our independence we do not run ads. We take no government funds. We run on donations which average $25. If everyone reading this would donate $5 then this fund raiser would be done in an hour. If Drugs-Forum is useful to you, take one minute to keep it online another year by donating whatever you can today. Donations are currently not sufficient to pay our bills and keep the site up. Your help is most welcome. Thank you.