Study of long-term side effects of morphine intrathecal administration in cancer pain model

镇痛剂量的IT吗啡和IT DEX输注产生耐受性。小剂量IT DEX与IT吗啡合用有明显的镇痛作用，且无耐受性。在注射吗啡的动物身上，可以看到在导管沿途有严重的脊髓压痕，表明肉芽肿的形成。加入小剂量的IT DEX可抑制IT吗啡注射诱导的肉芽肿形成和随后的运动障碍。然而，在癌症诱导的骨痛大鼠模型中，IT DEX和吗啡提供的止痛作用很小。加入地塞米松可抑制慢性IT吗啡诱导的耐受性和肉芽肿形成以及随后的运动障碍。联合应用IT吗啡和地塞米松可能有助于慢性癌痛患者避免副作用。

Analgesic doses of IT morphine and IT DEX infusion produce tolerance. Co-administration of low doses of IT DEX with IT morphine has significant analgesia without tolerance. Severe impression of the spinal cord along the course of the catheter indicating granuloma formation could be seen in morphine infusion animals. Addition of low dose of IT DEX inhibits IT morphine infusion-induced granuloma formation followed by motor impairment. However, IT DEX and morphine provided a littleanalgesic effects in a rat model of cancer induced bone pain. Development of tolerance and granuloma formation followed by motor impairment induced by chronic IT morphine were inhibited by addition of DEX. Combination of IT morphine and DEX may contribute to patients with chronic cancer pain to avoid side effects.