tokens: Capsaicin 100 micrograms was injected intradermally on the volar forearm followed by an i . v . infusion of ketamine ( bolus 0 . 1 mg kg - 1 over 10 min followed by infusion of 7 micrograms kg - 1 min - 1 ) , lidocaine 5 mg kg - 1 or saline for 50 min .