The effects of nefopam on blood acid-base status in the rabbit: interactions with morphine in the mouse and rabbit.

Nefopam, a non-narcotic analgesic, had only minor effects upon the blood pH, PCO2 and standard bicarbonate of the conscious rabbit. In contrast morphine caused a dose-dependent increase in PCO2 and standard bicarbonate. When nefopam was administered in conjunction with morphine (2.5 mg kg-1 and 1 mg kg-1 i.v. respectively) the increase in PCO2 was greater than with morphine alone. Nefopam also increased the antinociceptive and respiratory frequency depressant effects of morphine in the mouse.