Objective: To assess the benefit of ketamine addition to a morphine-clonidine-lidocaine mixture administered continuously by the intrathecal route for the treatment of cancer pain.
Study design: Case series analysis.
Patients and method: Four patients experiencing cancer pain with nociceptive and neuropathic components were treated with a continuous intrathecal administration of a mixture of ketamine (10 mg)-morphine (1-20 mg)-clonidine (30 micrograms)-lidocaine (20 mg) in 12 mL of normal saline, injected daily with an infusor (Baxter) pump. This treatment, associated with oral administration of sustained release morphine (SRM), was extended over 35 to 58 days, until the death of the patients.
Results: Either the secondary addition of ketamine to the morphine-clonidine-lidocaine mixture after the 40th and 15th days of treatment in patients no 1 and 2 respectively, because of a loss of efficiency of the mixture, or the immediate administration of the association of the four agents in patients no 3 and 4 provided efficient analgesia, unchanged over time, without significant adverse effects and allowed a decrease of the SRM doses.
Conclusion: Ketamine by intrathecal route potentiates analgesia obtained with morphine-clonidine and lidocaine, while impeding the development of a tolerance vis-à-vis the former.