Rifampicin - This is used for moderate to severe itching. Usually given if cholestryamine has been ineffective in helping the itch. Dosage begins at 150mgs daily.
It can sometimes cause nausea, and more significantly can cause some elevation in liver enzymes. When starting it, liver function tests should be done 2-4 weeks afterwards.
For some it has been very effective for many years controlling their itch. * It can cause your sweat and urine to be orange.. beware.