Paracetamol is one of the most commonly used drugs in the world, indicated for the symptomatic treatment of fever and pain of mild to moderate. More precisely, it is a drug used to relieve pain and reduce fever. The objective of this study is to analyze whether a placebo effect occurs when you take paracetamol for pain, ie if the analgesic effect of paracetamol is partly due to the simple fact of taking a drug.

Moreover, during the study you propose to do a saliva sample, optional, for biological research, pharmacogenetics, to assess how paracetamol is processed and eliminated in your body..

Clinical trial conducted in healthy volunteers, prospective, single center, randomized, open / hidden.

Inclusion Criteria:

- Healthy volunteers,

• Aged over 18 years and more than 50 years
• Males,
• Values of vital signs before administration of the test products:
• Systolic between 100-140 mm Hg
• diastolic between 50-90 mm Hg
• cardiac pulse between 45-90 beats per minute
• Free from any treatment in the 7 days preceding inclusion including no use of analgesics or anti-inflammatory)

Exclusion Criteria:

• Contraindications to the administration of paracetamol : Hypersensitivity to paracetamol, History of hepatitis B or C, Severe renal impairment
• Hepatic insufficiency
• Medical history and / or surgical judged by the investigator or his representative as being incompatible with the test, especially subjects with neuropathic pain,
• Pathology evolutionary time of the review of inclusion
• Excessive consumption of alcohol, tobacco (over 10 cigarettes / day), coffee, tea or drinks containing caffeine (equivalent to more than 4 cups per day) or drug abuse,