i asked the pharmacist about that at target when i found out that it's the same ingredient in the two, it's that benedryl contains it in a smaller amount. she said it's because it's an allergy medication they federally can't suggest people use it for inducing sleep even though it's commonly used for that.
i've tried dramamine for motion sickness before on plane rides. i didn't get sleepy, just very spacey and out of it.