For potentiation you would need more like 600mg Tagamet, probably. When people use it to potentiate benzos or opiates, they almost always have to take higher doses of it. I would just try the Butalbital on its own first but I don't know of your supply. Either way just be careful. Tagamet doesn't work for everyone either way. It mostly just potentiates opiates and increases the half-life of benzos. There's little to no evidence it does anything for Butalbital given the lack of info online about it.