Codeine is not necessarily the best choice bc it has too metabolized into morphine in the liver and that process may not workout fast enough. You should consider stronger opiates or TCAs (Amitriptyline). You can read about ODs in the PPeH.
This. Codeine's far too weak to be useful in any small capacity. You'd have to swallow a
lot to get it to work well, and even then good luck coughing up the cash for that.
If you opt for an opiod, morphine or anything stronger will do the trick, although you'll have to look around for some tablets, since oral solution is probably more likely to be vomited back up. SR tablets are a good shout, especially the non-capsule ones, because you can very easily crush them up to make them IR. I find capsules harder to do that with on account of the fact that it contains those tiny wax balls - chances are you'll never break
all of them fully open.
Couple the opiod of your choice (p.s, don't be conservative with the dosage) with the benzo and add in an antiemetic too, and you'll have a good cocktail for the bus.
As for antiemetics? Wikipedia's got a good list of ones to choose from. By far the best ones from what I hear are dopamine blockers, but any antiemetic will do in a decent enough dosage. If you don't grab dopamine blockers, or even if you do, look for medications that potentiate the effects. For example, morphine and other opiods tend to cause respiratory and CNS depression. Slower heartbeat, breathing, you start to black out, all that. But add in an antiemetic with those same properties and you're going to exacerbate the effect quite a lot, especially with the benzo making you feel a bit snoozy.
TL;DR: Benzo, antiemetic, opiod, and go nuts with the dosage if you're really into CTB.
