Two articles:

http://trynerdy.com/?p=1890

The first a warning about tetrahydrozoline.  Eye drops bought over the counter.  In the US two common brand names are VISINE and CLEAR EYES but suspect any eye drops your date may have on them.  As always, do not leave your drink unattended; keep it where only you can easily reach it, beware of being distracted.   Women have been known to use them on their dates as well to "escape" a bad date.  They drop your blood pressure, slow your heart rate and impair your breathing and make you drowsy.  "Just taking her outside for some fresh air." 

http://gizmodo.com/5829080/this-straw-might-prevent-date-rapes

The second, a new product being developed in Israel.  A straw that detects date-rape drugs.  "All you have to do is dip the straw in your drink and see if it lights up."

Of course, make sure you know the ID of your date and make sure others know or have seen him or, better yet, do a selfie with him and send it to a friend so he know's he's identified.  Of course, this comes with additional issues in our community, so use your judgement on how you protect yourself.  Nothing like him knowing that at least someone you know has seen him and can identify him.  PROTECT YOURSELF! Remember a weapon or a black belt in karate are useless if you are unconscious.

GGs know that leaving with a stranger is a risky behavior.