Analgesic effect of ketamine in a patient with neuropathic pain
Oye, I.; Rabben, T.; Fagerlund, T.H.
Tidsskrift for den Norske Laegeforening Tidsskrift for Praktisk Medicin Ny Raekke 116(26): 3130-3131
1996
ISSN/ISBN: 0029-2001 PMID: 8999575 Document Number: 464891
We report the effect of a single daily dose of ketamine in a 54 year old woman with fibromyalgia and severe post-traumatic neuropathic pain. A number of different approaches for pain relief had been tried with little effect. An intramuscular test dose of 0.4 mg/kg ketamine combined with 0.05 mg/kg midazolam lead to analgesia which lasted for almost two days. Long-term analgesia was also obtained by 250 mg ketamine hydrochloride taken orally in the form of capsules every night at bedtime. The patient has now used this dose for nine months. Ketamine is an NMDA receptor antagonist. A single sub-anaesthetic dose of ketamine causes a long-term depression of pain intensity in some, but not in all, patients suffering chronic pain. This effect is distinctly different from the short-lasting (10-30 min) analgesic effect in cases of acute nociceptive pain. The long-term depression of the intensity of chronic pain states may be due to a reversal of NMDA receptor-dependent long-term potentiation of synapses in central pain pathways. By giving ketamine as a single dose at night the mental side-effects are reduced or avoided.