Analgesic effect of subarachnoid neostigmine in two patients with cancer pain.

Two patients suffering with severe pain due to metastatic abdominal neoplasm were selected to examine whether subarachnoid neostigmine provided effective pain relief. Neostigmine was injected through a catheter introduced into the subarachnoid space at L4-L5. Patients were monitored for changes in arterial blood pressure, cardiac and respiratory rates, body temperature, level of consciousness and neurologic change. Pain was classified by the patients on a verbal four-grade scale, and analgesia was classified on a verbal three-grade scale. Complete pain relief was obtained 2 h after neostigmine (0.2 mg) in one patient and 4 h after neostigmine (0.1 mg) in the second patient. Pain of mild intensity returned 20 and 22 h after drug administration, respectively. Gastrointestinal discomfort was observed in both cases, but nausea and vomiting occurred only in the patient treated with the highest dose of neostigmine. No significant change in the monitored parameters was observed, except for a 6-h period of decreased blood pressure in the patient treated with the lower dose of neostigmine which required no specific treatment. The results obtained in these anecdotal cases indicate that subarachnoid neostigmine may provide analgesia in patients with pain arising from neoplasia, but further studies using controlled trials are needed before the drug is brought into clinical use.