Lack of tolerance to cyclopropane and cross-tolerance to halothane in rats

Cyclopropane requirement (MAC) in rats was determined before, during, and after repeated exposure to anaesthetic concentrations of cyclopropane and halothane for one hour every day for 20 and 30 days, respectively. MAC values during and after exposure ranged from 93 to 103 per cent (mean = 99 per cent) of control values, which indicates a lack of significant tolerance to cyclopropane or a cross-tolerance between cyclopropane and halothane.