I've used primidone (= desoxy)phenobarbital to withdraw from high dose clonazepam. Worked for that.
Primidone is approved for essential tremor (a neurological problem). It's anxiolytic properties seem not to be as strong as those of benzos at equivalent doses, at least for me. Taking it daily long-term for psychiatric disorders is a bad idea IMHO because it results in tolerance / dependence and eventually other psychological (and physical) problems. Primidone's active metabolite phenobarbital has a very long half life.
I'm aware its primary use is neurological disorders, hence the question. Since I've tried about every benzo typically prescribed, I thought I'd try something that relieves my worst symptom rather than anxiety itself.
That's quite disappointing though. One less option left for my anxiety.
I wouldn't say Primidone is no option for you. In general it helps with tremor at much lower doses compared with those used for epilepsy (e.g. 250mg vs. 1000-1500mg). This of course means fewer side effects. I think you can give it a shot and see how you react. Talk about it with your doctor.