Inclusion Criteria:  18-45 years of age Healthy Non-obese (body mass index less than 30 kg/m2) Body mass greater than or equal to 65 kg Speak English  Exclusion Criteria:  Subjects not in the defined age range Subjects who have cardiac, respiratory, neurological and/or metabolic illnesses Any known history of renal or hepatic insufficiency/disease Pregnancy or breast feeding Body mass less than 65 kg Current smokers, as well as individuals who regularly smoked within the past 3 years Subjects who cannot speak or read English Positive urine drug screen Currently taking pain modifying medication(s)