Paracetamol and Neuropathic Pain

Analgesic Effect of Paracetamol in Neuropathic Pain Patients

The aim of this study is to evaluate the analgesic effect of paracetamol in patients suffering from pain with a peripheral neuropathic component in the presence of their usual treatment.

This is an interventional, randomized, placebo-controlled, double-blind, crossover study about the use of paracetamol in therapeutic doses in peripheral neuropathic pain patients. The analgesic effect of paracetamol will be assessed by the painful intensity measured by numerical pain rating scale over one week after taking paracetamol/placebo.

The secondary objectives will be:

• To determine the number of patients in whom paracetamol is effective in reducing pain by at least 30% and 50%,
• To evaluate the effect of paracetamol on pain, on the number and intensity of paroxysms,
• To evaluate paracetamol consumption,
• To evaluate the effect of paracetamol on neuropathic pain patient,
• To evaluate the effect of paracetamol on mechanical allodynia,
• To monitor routine biological parameters (liver function),
• Compare Glutathione (GSH) concentrations before and after taking paracetamol,
• To perform a blood test for paracetamol and its metabolites before and after each study period,
• To perform urine dosage of paracetamol and its metabolites before and after each study period,
• To study pharmacogenetics parameters,
• To evaluate patient feeling and satisfaction after taking paracetamol,
• To evaluate the effect of paracetamol on cognition, anxiety, depression and sleep by different questionnaires,
• To collect adverse events.

Inclusion Criteria:

• Patient aged 18 to 65 years,
• Patient suffering from chronic pain (for more than 3 months) with the characteristics of peripheral neuropathy and having pain assessed by a numerical scale ≥ 3 for one week, with at least 10 assessments completed,
• Patient agrees with not to take paracetamol, other than the treatment provided as part of the protocol, from inclusion to completion of the study,
• Acceptance to give a written consent.

Exclusion Criteria:

• Patient taking paracetamol daily,
• Patient with a contraindication to paracetamol administration (liver or renal failure, ...),
• Patient with a biological evaluation evaluated by the investigator as not compatible with the trial,
• Patient with a medical and/or surgical history evaluated by the investigator to be not compatible with the trial,
• Patient with drug treatments evaluated by the investigator to be not compatible with the trial,
• Pregnant or nursing woman,
• Patient with a cooperation and an understanding that does not allow for a strict compliance under the conditions set out in the protocol,
• Patient participating in another clinical trial, or being in an exclusion period, or having received a total amount of compensation exceeding 4500 euros over the 12 months preceding the start of the trial,
• Patient benefiting from a legal protection measure (curatorship, guardianship, protection of justice...),
• Patient not affiliated to the French Social Security system,
• Paracetamol intake during wash-out period.