Pain remains the leading cause of consultation. Despite a wide therapeutic arsenal, a significant percentage of patients disclaim little or no pain relief with common analgesics, specific or not their type of pain. This is especially true in cases of chronic pain, and current treatments are associated with many side effects. A need for therapeutic innovation is needed. Paracetamol is currently the most widely used analgesic worldwide but despite its excellent safety, its analgesic effect is limited from moderate to severe pain. Many analgesic drug combinations include paracetamol, recently the co-administration of paracetamol and nefopam showed a supra-additive antinociceptive effect (Van Elstraete AC et al. 2013). The development of a formulation associating paracetamol and nefopam first requires searching a possible pharmacokinetic interaction between the two active substances and assessing safety of this combination in healthy volunteers. No published studies providing such information.

This is a randomised, cross-over, open label trial assessing drug interaction between paracetamol and nefopam in healthy volunteers.

Inclusion Criteria:

• Age over 18
• ALT, AST, PAL, normal GGT, creatinine <133μmol / L, hematocrit>38%
• Informed consent to the trial
• Healthy volunteers affiliated to the French Social Security