Mean maximum arterial plasma nicotine concentrations ( C ( max ) ) were 2.11 , 3.73 , and 4.38 ng/mL and mean times to C ( max ) were 10.2 , 7.3 , and 6.5 min after the start of inhalation for the 0.22 , 0.45 , and 0.67 mg doses , respectively .