That is dangerous advice mr tambourine man!
It has already been stated why it is dangerous.
Clonidine is not an alphablocker, there are two types of alpha receptor, alpha1 and alpha2. Alpha1 controls vasoconstriction/vasodilation, an alphablocker is a hypotensive drug. Clonidine is an alpha2 adrenoreceptor agonist. The alpha2 receptor (which has subtypes, alpha2a, alpha2b, alpha2c and possibly, can't remember for sure, but I think there might be an alpha2d...POSSIBLY...I may well be mistaken there, its been a while since I read up on alpha2 receptor subtypes and I am very tired, 20 hour days will do that to you)
Alpha2 is what is called an autoreceptor, autoreceptors essentially act as a feedback mechanism, reducing neurotransmitter release when stimulated, an alpha2 antagonist (yohimbine being a prominent example) blocks alpha2 receptors, resulting in the brain getting the message 'noradrenaline release needs to occur, less stimulation of alpha2 means less noradrenaline is present, need more', clonidine, tizanidine, guanfacine (a subtype selective alpha2 agonist, used as a nootropic, to aid concentration and memory...I wish it was used here in the UK, or I would have had my tizanidine script changed ages ago) and the three I really want to try sometime, romifidine and xylazine, and dexmedetomidine do the opposite, in effect, turning down the gain control, as the brain is getting the signal that there is too much noradrenergic activity and to lessen release of NA.
This is the safer option here, beta blockers are dangerous with stimulants, you are unlikely ever to see clinical use of a beta blocker, for instance, for treating the hypertension associated with cocaine overdose, the adrenergic/noradrenergic activity, being unable to stimulate beta adrenoreceptors as normally happens without the beta blocker, well, the neurotransmitter has to go somewhere, aside from being broken down by monoamine oxidase, can't bind to beta receptors, so it has only alpha adrenoreceptors to bind.
The result is paradoxical from what one could expect from a hypotensive drug, with alpha1 mediated vasoconstriction occuring, and trouble following.
I've been on both, beta blockers and alpha2 agonists. I'm autie, and both have been tried for overstimulation and sensory overload. Fucking hated propranolol, it was active only on peripheral symptoms such as rapid heart rate if I got overloaded, piloerection, etc. Think yes, the opposite, WITHOUT amphetamine being present in the users system, only a betablocker, of the peripheral effects of ephedrine, subjectively that is. Lowered heart rate, lowered BP, less tendency for sweating of palms if it is scripted to an anxious patient. Will steady shaking of hands/fingers or voice also, but thats more or less what you get.
I have taken it when anxious, and thats all it did. No use for the psychological/central bits of an anxiety response. I'm not an anxious person myself, not without a reason at least, but the only thing it made me feel was shitty.
I used to have a clonidine rx, now its tizanidine, although I preferred clonidine really, tizanidine is way too short acting for my liking although its really useful to me. They ARE effective in cases of stimulant comedowns, I wouldn't want anything to do with stimulants without one or the other drug. They are strong hypotensive agents, clonidine being much much more powerful in dropping BP, lower heart rate, good for anxiety, although a side effect is fatigue, which on a large dose can be extreme, and make it too much to carry on a task. Depends on the route of administration also. Good for stopping the hyperstimulation, restless legs (and the rest of one's body) that is caused by opioid withdrawal also. Orally is less likely to make one too tired. At least in the case of tizanidine.
Plugged in solution or insufflated in a low dose can dramatically increase the sedation and nodding on an opioid, and its one of the very few things, short of the times I have had medical procedures, like knee surgery and a general anaesthetic combination has been used that will knock me out cold or sedate me in a manner that actually makes me sleep. I have had trouble gettin GABAergics to work effectively as a sleep aid. Without a tolerance to them, monstrous doses of nitrazepam have effectively just made me feel better about not being able to sleep, I've had to be switched from that to a non-benzo, that acts more like a barbiturate to have something for that purpose that actually works. Tizanidine though, plugged, will literally knock me out until it wears off in perhaps 10-15 minutes at most.
So, much better, safer choice for stimulant related use. Alpha2 adrenoreceptor agonists are also strong myorelaxants.