Melatonin works best when your sleep cycle is messed up, thus leading to insomnia. If you go to bed at the same time every night, but can't fall asleep, it probably won't work since low melatonin levels is likely not the problem.
And what is this based on? Just pulled it straight out your ass?
This is what I was basing my comments on.
http://www.ncbi.nlm.nih.gov/pubmed/7028792?dopt=AbstractAnd as the study shows, it is actually CBD, as opposed to THC which gives Marijuana its hypnotic properties. Perhaps if we had rational laws regarding Marijuana, Clarence could get a CBD capsule and maybe it could work for him without the other effects caused by THC.