Llamas were given each of four treatments intramuscularly with a 1-week washout : TZ ( 2 mg kg ( -1 ) ) combined with either morphine ( 0.5 mg kg ( -1 ) ; M ) , xylazine ( 0.15 mg kg ( -1 ) ; X ) , morphine ( 0.5 mg kg ( -1 ) ) and xylazine ( 0.15 mg kg ( -1 ) ) ( MX ) , or saline ( C ) .