They are practically blood pressure pills, my friend - they are very similar pharmacologically-speaking to clonodine which is an antihypertensive (lowers high blood pressure in (mostly old) people). Unless you want to potentiate the low blood pressure produced by opioids (aka worsen that undesirable side effect), they're essentially useless.
Sorry but 'is this recreational?' threads aren't allowed in here so I'm going to close this but please feel free to PM me or the BDD mods if you have any questions.