Study To Assess The Effect Of Gabapentin, Diphenhydramine And Morphine On Cold Pain In Healthy Male Volunteers

• Drug: Gabapentin
  
  Capsule, single 1200mg dose
• Drug: Diphenhydramine
  
  Tablet, single 50mg dose
• Drug: Morphine
  
  IV, single 10mg dose
• Drug: Placebo
  
  Placebo formulations (Capsule, tablet, IV to match the active treatments and to be administered in a double-dummy fashion).

• Active Comparator: Gabapentin 1200mg
  
  Intervention: Drug: Gabapentin
• Active Comparator: Diphenhydramine 50 mg
  
  Intervention: Drug: Diphenhydramine
• Active Comparator: Morphine 10 mg
  
  Intervention: Drug: Morphine
• Placebo Comparator: Placebo formulations
  
  Intervention: Drug: Placebo

Inclusion Criteria:

• Healthy male volunteers having given consent to participate in the study who have no clinically significant anomalies and whose vital signs are within normal range.
• Subject having performed the cold pain test reproducibly ie, if the area under the pain-time curve (AUC) must be within 20% during successive tests within one cold pain test screening visit and within 30% between the two cold pain test screening visits.

Exclusion Criteria:

• Subject who have had a serious adverse reaction or significant hypersensitivity to any of the study drugs.
• Subjects with a history of or evidence of any neurological condition which could affect pain sensation.
• Subjects with an AUCcpt 0-120 sec in the cold pain test of <1000 in any of the screening tests (excluding familiarization).