I think it's going to depend a lot on what your opiate tolerance is, what drug you're utilizing the synergy of, dosages, unique effects that may or may not be a general trend among users or a person-by-person unique reaction...etc
For instance, if I take benzodiazepines and/or antihistamines to potentiate buprenorphine, I'm not going to notice buprenorphine tolerance growing.
If you use drinking alcohol in order to boost the effects of benzodiazepines, you bet your ass there'll be a tolerance increase.
If you're using tramadol/codeine/hydrocodone to potentiate oxycodone/morphine/oxymorphone/heroin/fentanyl, then yeah, tolerance is going to grow.
IME, if you're using cannabis to potentiate opiates, I don't think you're going to notice an actual tolerance to the opiates. You will likely be able to go back to not using cannabis with your opiates, and won't need a higher dosage.
If you're using methamphetamine to potentiate opiates (
horrible fucking idea), it will raise your opiate tolerance. The reason being is that methamphetamine reduces the effects of
all other recreational drugs either from a slight to heavy degree. For instance, if you're going to be using a point of heroin to get a mild buzz or nod (if you're still lucky and have low tolerance), just being on methamphetamine, will require you to use at least 2x as much opiates to attain the same opioid effects. The synergy will be there, especially due to how good you'll feel. However, it does lead to a raised tolerance.
The same goes for benzodiazepines and methamphetamine. Off methamphetamine, 1mg alprazolam is felt strongly. On (a mild dosage) of methamphetamine, 2mg of alprazolam might not even deliver 50% of the effects that just one 1mg alprazolam would without methamphetamine in the system.
One last example for a "person to person" type unique reaction... take psychedelics and opiates. I have done LSD + heroin several times. Some people really,
really,
really enjoy this combination. They claim it's the perfect way to balance out the stimulant-type effects of LSD as well as increasing visuals. However, other people feel the heroin dulls down the psychedelic visuals/feel to the trip. And yet other people may feel the heroin over powers the LSD, and other people might even say LSD would over power the effects of the heroin.
So all in all, opiate potentiation isn't exactly black and white; there's lots of unique outcomes here, so everyone, please be careful when consuming drugs.
