So I certainly can provide some insight. I'm not going to give any of the classic judgemental or suggestive recommendations, I'm going to answer your question with knowledge gained through years of experience and study into the safest usage of DXM.
First things first, you want to be sure that you get DXM. There are two different "variants" you want to be familiar with. The first is dextromethorphan HBr, which is dextromethorphan hydrobromide. DXM HBr can be considered rapid-release DXM, and is the one typically sought out. The second type is dextromethorphan polistirex, which is found in most Delsym cough syrups. This is extended-release and though less sought, I prefer it. We'll get to that though.
Starting with the more common DXM HBr.. You can find this at most places that sell OTC medicine. Don't look for brands, look at the labels. If you can find pills that contain only dextromethorphan HBr, this is obviously preferable to drinking a syrup that contains the same. Simply put, it's easier to swallow some pills than it is to drink thick gross syrup. Don't buy any pill or syrup that contains additional ingredients like guaifenesin, phenylephrine, acetaminophen, or anything else. All you want is dextromethorphan HBr. Once you've found that, you're golden. As a 140lb male, I'd suggest starting with 300mg DXM HBr. You have to understand though, effects with these types of dissociative are not linear. That considered, this is a safe does that'll give you a good feel for the experience. I'd also suggest NOT taking all 300mg at once. Your body has to metabolize this stuff, so it's okay to do it in stages.. a good plan would be taking the 300mg over an hour, with 75mg doses every 15 minutes. Doing it this way will also allow a slower onset, which is preferable in any first time experimentation.
Now, say you want to go about it a different way and want a longer trip. For this, I recommend dextromethorphan polistirex. Doing a simple cold-water extraction, you can easily take the whole bottle's worth in one shot. Now, you're looking for a little higher dose due to the extended release. I'd suggest 400mg dxm polistirex, which will be a solid 2nd plateau trip.. potentially a low 3rd plateau. Buy some Delsym or cheap equivalent that ONLY has dextromethorphan polistirex. Buy enough where you can separate enough syrup that it contains 400mg dxm polistirex. Also purchase a large gallon sized zip lock bag. When home, fill the zip lock bag with cold water and pour in your syrup with a 400mg dose of dxm polistirex. Close it, and shake that thing around to mix it evenly. Now clip or hang the bag from one of it's top corners and wait about an hour. When you return, you'll see that a bunch of orange sand looking stuff has collected at the bottom corner. Drain the water (carefully) above the sandy orangeness. That stuff is the dxm polistirex separated from the syrup. Once enough water is gone, you can mix it in come chocolate milk or dry it and put the powder in a gel-cap pill. Trust me, it's not all that complicated lol. I prefer this method, as I am removing anything in the syrup that came from the manufacturer. With only water, you get pure dxm polistirex.
In closing, either way you go.. the importance can't be stressed enough that you take a safe starting dose and that you avoid anything that isn't dxm HBr or dxm polistirex. Also, start low. There are plateaus and the effects between one and the next can be drastic. In the 2nd to 3rd plateau, it's probably good times. 1st plateau is pointless. Once you get into the 4th plateau and above, things become truly experimental and potentially dangerous. The good thing is, if you are careful on dosing, you shouldn't have any issues. Again, start low and work your way up. You don't have to punch a ticket to oblivion during your first dxm trip.
Happy and safe travels my friend.
