This study aims to evaluate the analgesic efficacy of single and repeated doses of fixed combination of dexketoprofen trometamol (DKP) and tramadol hydrochloride (TRAM) in comparison to the single agents (and placebo for the single dose phase only) Approximately 600 male and female patients presenting moderate to severe pain after an elective primary hip arthroplasty are eligible to be randomised provided that they experience moderate to severe pain on the day after surgery.

In this clinical trial patients were randomized to the described 6 treatment arms, where each arm define the treatment to be received in the first single dose phase (lasting 8 hours after the 1st treatment intake) and in the subsequent multiple-dose phase (lasting from the second treatment intake up to the 8 hours after the last intake). Namely:

• DKP/TRAM followed by DKP/TRAM;
• DKP followed by DKP;
• TRAM followed by TRAM;
• placebo followed by DKP;
• placebo followed by TRAM;
• placebo followed by DKP/TRAM;

The analyses of endpoints pertinent to the single dose phase were performed combining all the 3 treatment arms including placebo into one group, which resulted in the following 4 analysis groups: DKP/TRAM, DEXKETOPROFEN, TRAMADOL, and Placebo.

The analysis of endpoints pertinent to the multiple dose phase were performed combining the treatment arms including the same active treatment, which resulted in the following 3 analysis groups: DKP/TRAM, DEXKETOPROFEN, and TRAMADOL.

Inclusion Criteria:

• Male or female patients aged 18 to 80 years. Females participating in the study must be either of non-childbearing potential, or willing to use a highly effective contraceptive method.
• Scheduled to undergo standard primary (first-time) one-sided total hip replacement surgery due to primary osteoarthritis.
• Patients experiencing pain at rest of at least moderate intensity the day after surgery.

Exclusion Criteria:

• Patients not suitable for study treatments and rescue medication (RM) or those for whom non-steroidal anti-inflammatory drugs (NSAIDs), opioids, acetyl salicylic acid, pyrazolones or pyrazolidines are contraindicated.
• Patients with clinically significant abnormalities in vital signs, safety laboratory tests and 12-lead ECG at screening.
• Patients with history of any illness or condition that might pose a risk to the patient or confound the efficacy and safety study results.
• Patients using and not suitable to withdraw analgesics other than those specified in the protocol.
• Patients using and not suitable for withdrawing any of the prohibited medication specified in the protocol.
• Pregnant and breastfeeding women.