This is why antiemetic abuse is generally not a problem for healthy people, because they might have one bad trip like greasydago did and never want to do it again. Drugs like phenegran are most dangerous for young children and people with severe breathing and cardiac problems or a severe allergy to the drug otherwise greasydago's outcome and some constipation is generally the worst likely outcome. This all changes if you mix it with alcohol and other drugs, then you must be very careful and do not make any combinations that you haven't checked out thoroughly preferably with a medical professional. I always check combinations and doses on sites like fda.gov and drugs.com, but if in doubt, ask a medical professional before you act, but those sites will get you close in terms of correct dosing. I also think you should use your antiemetics as rarely as possible so they will pack the most punch when you need them. It may be that continued use doesn't reduce their effectiveness, but it definitely lowers their effect on you in terms of side effects like drowsiness so I think that means that at least in some ways your body does get used to them.