Juliet, while I certainly do see your point, and just making it different because she is a woman would definitely be wrong, there is one big difference imho between what the potency drug did and what a date rape drug does.
The potency drug just affected Clark on a physical level, just like a laxative would. So, would a guy get arrested for putting a laxative into a woman's drink and she had then urgent business to attend to? Or would he only get arrested later on because she slept with him after she felt well enough for such things? To very unrelated actions, mind you, if you discount her perhaps feeling not up to her game that night.
And I'm sorry if the example is a bit far fetched or, um, not appropriate, but I can't think for the life of it of another drug that only has a (to a healthy person) harmless physical effect. And laxative-jokes are not that uncommon on TV anyway. (Think laxative chewing gum and the likes offered to a rival.)
But on a different note, your comments about soul mates gave me some very nice little plot bunnies on who to get from A to C to E, with B and D being unknowns before. So thanks a lot
Michael