BACKGROUND AND OBJECTIVE: The combination of opioids with supplemental analgesics is commonly used for additive or synergistic analgesic effects. We aimed to determine the most advantageous supplemental analgesic for postoperative pain relief after lumbar disc surgery. METHODS: This prospective, placebo-controlled, randomized, double-blind study compared the effects of intravenous metamizol, paracetamol and lornoxicam on postoperative pain control, morphine consumption and side effects after lumbar disc surgery. Eighty patients with American Society of Anesthesiologists classification 1 or 2 scheduled for elective lumbar disc surgery under general anaesthesia were treated using patient-controlled analgesia with morphine until 24 h postoperatively and randomized to receive additional intravenous injections of metamizol 1 g, paracetamol 1 g, lornoxicam 8 mg or isotonic saline 0.9% (placebo). The primary endpoint was pain over 24 h after surgery measured by visual analogue scale. Secondary endpoints were morphine consumption and side effects. RESULTS: During the 24 h study period, pain was reduced in the metamizol (P = 0.001) and paracetamol (P = 0.04) groups, but not in the lornoxicam (P = 0.20) group compared with the control group. Further analysis revealed that pain scores in the metamizol group were significantly lower than in the lornoxicam group (P = 0.031). Although the rate of morphine consumption in the paracetamol group was decreased over time (P < 0.001), the total amounts of morphine consumed in 24 h were not different between groups. No significant differences with respect to morphine-related side effects were observed between groups. CONCLUSION: Metamizol or paracetamol, but not lornoxicam, provides effective analgesia following lumbar disc surgery.