Patient-controlled analgesia with morphine plus lysine acetyl salicylate

Using a patient-controlled analgesia (PCA) delivery system, we evaluated the clinical advantages and disadvantages of morphine PCA compared with morphine plus lysine acetyl salicylate (LAS), a soluble aspirin. After major orthopedic surgery, 50 adult patients were enrolled in a prospective, randomized, and double-blinded study. When a patient in the recovery room complained of pain, an initial dose of morphine or the morphine/LAS mixture was titrated to achieve analgesia of visual analog score less than or equal to 3 in 30 min. An equivalent volume PCA dose of either morphine 1 mg/mL or morphine 0.5 mg + LAS 90 mg/mL was used with a lockout interval of 10 min. Pain score, patient satisfaction, vital signs, and adverse effects were observed for 48 h. Adequate analgesia (visual analog scale score less than or equal to 3) was achieved with either drug. Morphine consumption in the morphine/LAS group was significantly less than in morphine group (13.9 vs 18.4 mg in 24 h and 24.3 vs 32.4 mg in 48 h). Significantly more sedation was evident with the morphine group (P < 0.05). We conclude that injectable LAS can be used as an effective and safe adjuvant to morphine for PCA. This combination reduces dose requirements of morphine and hence some of its adverse effects. Implications: Injectable aspirin could be used as an effective and safe adjuvant to morphine for patient-controlled analgesia. This combination reduces the dose requirement of morphine and therefore some of the morphine-related untoward effects.