How do you manage severe chronic scalp pruritus in older women when biopsies and exams show no primary skin disease and standard therapies fail?

I use gabaergic drugs like Pregabalin and Gabapentin in high doses up to 300 mg and 3600 mg, slowly tapering up as many of these cases are neuropathic. I use compounded topical KAL cream 10% ketamine, lidocaine 5, and amitriptyline 5, or foam formulation or pramoxine lotion bid or topical compounded...