MILAN, ItalyA small Italian study of gabapentin (Neurontin) in
patients with neuropathic cancer pain only partially responsive to
opioid therapy suggests that the anticonvulsant may have a role to
play in this situation.
Although the usefulness of gabapentin as an analgesic has been
studied in several neuropathic pain syndromes, no report is
available at the moment about the use of this drug as an adjuvant
analgesic in cancer pain, said Augusto Caraceni, MD, and his
colleagues in the Pain Therapy and Palliative Care Division, National
Cancer Institute of Milan.
The researchers studied 22 consecutive patients with neuropathic
cancer pain that was not completely controlled with opioid analgesics
or in whom the opioid dose was limited by side effects. Neuropathic
pain was defined as pain due to a peripheral neurologic lesion caused
by cancer and included at least one of the following symptoms:
burning pain, paroxysmal episodes of shooting pain, or pain with
light touch (allodynia).
Global pain and burning pain intensity were assessed on a scale of 0
to 10; paroxysmal pain episodes were quantified as approximate number
per day. Allodynia was rated as present or absent after the skin was
gently brushed with cotton or lightly stimulated with a finger.
Patients underwent a dose titration period of 3 to 7 days, using 300-
or 400-mg gabapentin capsules, to optimize analgesia while keeping
the opioid dose stable. Pain and side effects were assessed at
baseline and when the patient had reached a stabilized gabapentin
dose (at least 3 days without a dose change)after 7 to 14 days
The mean daily gabapentin dose was 1,004 mg (range, 600 to 1,800 mg),
while the mean opioid daily dose was 147 mg (range, 20 to 900 mg). In
all patients, opioid dose remained stable during the study period.
Pain Scores Decreased
With use of gabapentin, mean global pain scores decreased from 6.4 to
3.2. Burning pain intensity decreased from a mean of 5.1 to 2.0.
Episodes of shooting pain fell in frequency from 7.2 per day to 2.2
per day. Allodynia was present in nine patients at baseline, and it
disappeared in seven after gabapentin use (J Pain Symptom Manage
Of the 22 patients, 20 judged gaba-pentin as efficacious in reducing
their painful neuropathic symptoms. Of the other two patients, one
had complete control of lancinating pain but no change in constant
pain. The other patient had rapidly progressing malignant melanoma
that had invaded the brachial plexus.
Side effects did not change with the addition of gabapentin, with the
exception of one case of increased sedation and one of new-onset dizziness.
Dr. Caraceni noted that the mechanism of gabapentin analgesia in
animals has been linked to an interaction with the N-methyl-D-aspartate
receptor system. This raises the possibility that gabapentin
can interfere with some of the mechanisms of opioid resistance often
considered associated with the clinical phenomena of neuropathic pain
and tolerance, he said.
He added that gabapentin has no major drug interactions and does not
increase hepatic enzymes. It might therefore be an attractive
adjuvant drug in advanced cancer patients who already are on multiple
medications and have altered metabolic functions, Dr. Caraceni said.
He concluded: Controlled clinical trials are needed to confirm
whether gabapentin is indicated for specific cancer pain syndromes,
to show dose-effect relationships, and to compare it with other