Effect of High-dose Naloxone Infusion on Pain and Hyperalgesia in Patients Following Groin-Hernia Repair.

Inclusion Criteria: * Age ≥ 18 years and ≤ 65 years * Signed informed consent * Patients submitted to unilateral, primary inguinal, open herniotomy 6-8 weeks prior to study start. * Open operating procedure a.m. Lichtenstein. * Urin sample without traces of opioids (morphine, methadon, buprenorphine, codeine, tramadol, ketobemidone, oxycodone, hydromorphine, dextromethorphan) * ASA I-II * Body mass index (BMI): 18 \< BMI \< 30 Exclusion Criteria: * Volunteers , who do not speak or understand Danish * Patients, who cannot cooperate with the investigation * Patients who have had previous surgery in the groin region * Patients with pain at rest \> 3 (NRS) * Activity-related pain in the surgical field \> 5 * Allergic reaction against morphine or other opioids (including naloxone), * Abuse of alcohol or drugs - according to investigator's evaluation * Use of psychotropic drugs (exception of SSRI) * Neurologic or psychiatric disease * Chronic pain condition * Regular use of analgesic drugs * Skin lesions and tattoos in the assessment areas * Nerve lesions in the assessment sites (for instance, after trauma, disc herniation, etc.) * Use of prescription drugs 1 week before the trial * Use of over-the-counter drugs 48 hours before the trial