when I was in st. louis the popular cut was Dormin, which is Diphenhydramine. you can also use name brand benadryl (the capsules, not the pills), so Dormin brand or Benadryl. the generic benadryl gels up for whatever reason.
but even when shot alone, Diph gives a decent feeling rush, and if done with opiates adds to the rush, and nod, and helps cut down on itch (you're gonna itch anywayz, which I still like).
I also notice that phenergen (or promethazine, which is actually what I got in pill form) is an antihistamine and I wouldn't say it has a rush, but you immediately wanna lay down and sleep. but I think that one is a little heavy of a cut unless if only used in small amounts, the pills I got are 25mg, and they make me sleep.
but yeah, I'm stoned and morphed and rambling so anyayz Diphenhydramine is a decent cut thats not any worse than shooting the dope.