Here's a reminder that xylazine itself can create a withdrawal syndrome (although this is still fortunately rare). This is an evolving and new area of exploration, but here's the general approach to treating it:
For milder symptoms, first recommendation would be to start with 0.1 mg clonidine TID
Titrate this up to 0.3 mg TID as tolerated (would require hospitalization or a patient reliable enough to dc and self-titrate)
If this fails, add on a GABA-ergic agent
Gabapentin 300-600 mg TID-QID
Benzos (any!) or phenobarbital, similar to how you might use it for EtOH dependence
Adjuncts like hydroxyzine or olanzapine, typical doses
all the way up to
Dexmedetomidine (Precedex--clonidine's big kahuna relative)
Ketamine, typical agitation doses
Keep in mind that most of the time, you'll be treating a very significant opioid dependence at the same time, so first priority will often be to be controlling that as aggressively as you need to. The extent of treatment these patients can require is illustrated nicely in the sole case report with clinical detail that we have for in-hospital management of xylazine dependence, concomitant with opioid dependence (in brief, it involved a opioid PCA, a micro-dosed transition to buprenorphine, a phenobarbital taper, spot ketamine, gabapentin, and a 19-day hospital stay).