Efficacy and safety of oral ketamine for the relief of intractable chronic pain: A retrospective 5-year study of 51 patients.
BACKGROUND
This work summarizes the efficiency, failures and adverse effects of oral administration of ketamine at home for intractable pain.


METHODS
This 5-year retrospective study involved testing ketamine by intravenous in-hospital administration, then a conversion to an oral route, or oral treatment directly administered at home. The daily intravenous dose was increased by steps of 0.5 mg/kg to attain an effective daily dose of 1.5-3.0 mg/kg. Pain was evaluated on a numeric scale from 0 to 10, and evidence of adverse effects was collected every day. The effective daily dose was delivered orally (three to four intakes). If effective, ketamine was continued for 3 months. Short infusions or direct oral treatment began with a 0.5-mg/kg dose, then the daily ketamine dose was increased in 15- to 20-mg increments.


RESULTS
Among 55 cases (51 patients, neuropathic pain 60%), the mean effective oral dose was 2 mg/kg. Ketamine was effective in 24 patients (44%, mean pain reduction 67 ± 17%), partially effective in 20% (mean pain reduction 30 ± 11%), with a mean opioid sparing of 63 ± 32%, and failure in 22%. Half of the patients experienced adverse effects, but only eight had to stop treatment. For patients with opioid therapy, failure of ketamine was less frequent (7% vs. 36%; p < 0.02), with fewer adverse effects (33% vs. 68%; p < 0.01).


CONCLUSIONS
Pain was reduced or abolished in two-thirds of patients under ketamine therapy; ketamine was effective for patients taking opioids and resulted in few adverse effects.
Unité d'évaluation et de traitement de la douleur, Groupe hospitalier Pitié Salpêtrière, Paris, France.
F
F
Marchetti
Unité d'évaluation et de traitement de la douleur, Groupe hospitalier Pitié Salpêtrière, Paris, France.
A
A
Coutaux
Unité d'évaluation et de traitement de la douleur, Groupe hospitalier Pitié Salpêtrière, Paris, France.
A
A
Bellanger
Unité d'évaluation et de traitement de la douleur, Groupe hospitalier Pitié Salpêtrière, Paris, France.
C
C
Magneux
Unité d'évaluation et de traitement de la douleur, Groupe hospitalier Pitié Salpêtrière, Paris, France.
P
P
Bourgeois
Département d'anesthésie-réanimation, Hôpital Cochin, Paris, France.
G
G
Mion
D061605:Administration, Intravenous; D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D059350:Chronic Pain / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007649:Ketamine / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000188:drug therapy; D010147:Pain Measurement / Q000187:drug effects; D010148:Intractable Pain / Q000188:drug therapy*; D061214:Patient Safety; D012189:Retrospective Studies
D000701:Analgesics, Opioid; D000778:Anesthetics, Dissociative; D007649:Ketamine