The present study contrasted the pharmaco-economics and analgesic efficacy of intramuscular (i.m.) opioid treatment with a parenteral disposable patient-controlled analgesia (PCA) system in two groups of 20 female patients (ASA I-II, aged 35-69 years) scheduled for abdominal hysterectomy. The PCA group received a continuous infusion of 1.5 mg h-1 piritramide, a mu-opioid receptor agonist, with incremental doses of 1.5 mg (lock-out interval = 15 min). The i.m. group received 0.3 mg kg-1 piritramide i.m. when requested by the patient with a minimum interval of 5 h. Pain intensity, sedation and the functional recovery of the patients were followed for 72 h post-operatively. The sum of pain intensity differences (SPID) was used as a measure of analgesic efficiency. Equipment and drug costs, and the demand on nursing time were recorded over 3 days post-operatively. The costs of PCA and i.m. therapies per patient were used to calculate the cost-benefit (cost of treatment vs. nursing time) and cost-effectiveness (cost of treatment vs. SPID) analyses. Both treatments initially provided comparable analgesia, but PCA was more efficient after 16 h and significantly reduced nursing time for pain treatment (PCA = 61 +/- 4 min, i.m. = 88 +/- 5 min; P < 0.001). Functional recovery was not different for either treatment. Cost analysis indicated a better cost-benefit ratio for the i.m. treatment (0.35 vs. 1.1 for PCA treatment), but a similar cost-effectiveness for both treatments (PCA = 1.9 Belgian Francs (BEF) unit-1 SPID; i.m. = 1.7 BEF unit-1 SPID).