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Low-Dose Effexor Palliates
Pain of Peripheral Neuropathy
Summary
Low-dose Effexor (venlafaxine hydrochloride)
successfully palliates the pain of peripheral neuropathy (PN)—although not
the numbness. In addition to a personal verification of this, there are
published articles describing this use. This drug is psychoactive
antidepressant, and it has many potential side effects; therefore, the user
should carefully review the PDR prior to using Effexor. At high doses
(75-225 mg/day), the drug will likely cause serious nausea and result in a
continuously drugged feeling. Consequently, it is recommended that you begin
with a dose of 10 mg a day. After 5 days, you can go to 10 mg b.i.d. At
these levels, the side effects seem to be trivial. It is necessary to cut
the tablets or to divide up the granules in the XR capsules to obtain a 10
mg dose.
In my own case, the neuropathy pain disappeared within a few days, but I
needed to take the second dose to gain the benefit 24 hours a day. Even at
these doses, the drug has a noticeable antidepressant effect. It is not
known whether this treatment will lead to permanent palliation of the PN
pain.
Background
It has long been known that antidepressants help to
reduce the pain of neuropathy. Egbunike [1] reported in 1990 on the use of
antidepressants to palliate the pain of diabetic neuropathy, neuralgia, and
phantom limb pain. He pointed out that the analgesic effects were separate
from the antidepressant effects and that doses used for pain were generally
lower than those used to treat depression. He recommended that doses “should
be started low and gradually increased until the patient reaches the highest
tolerable dose. Onset of analgesia is variable, ranging from 1 day to 10
weeks.” He did not establish optimum dosages.
In my case, I started at 9 mg q.d., then increased to 9 mg b.i.d. after 4
days. The pain disappeared by the time I was taking two doses a day. Since I
have continuous-release capsules of 75 mg each, I poured out a circle of the
beads to about the diameter of the capsule. That yielded about 9 mg/day. One
could order capsules containing 37.5 mg each. The other alternative is to
order the immediate-release tablets of 37.5 mg each and cut them twice with
a pill cutter. I do not know what the difference in response will be between
the XR capsules and the immediate-release pills. At this point, my
recommendation would be to use either form of the 37.5 mg dose—pill or XR
capsule.
Egbunike used an antidepressant called amitriptyline, one of a group of
tricyclic (having 3 organic rings) depressants. Kalso [2] reported in 1996
on the use of amitriptyline to relieve neuropathic pain in the arm and
around the surgical scar following a breast cancer operation. Eight of 15
patients had at least a 50% decrease in pain intensity. The problem,
however, is that the “adverse effects of amitriptyline put most of the
patients off from using the drug regularly.” Enter venlafaxine
hydrochloride.
In a murine experiment, Lang showed that venlafaxine
HCl—a new antidepressant--reduced the pain due to induced neuropathy [3].
Further, the PDR [4] reports that Effexor “is chemically unrelated to
tricyclic, tetracyclic, or other available antidepressant agents.” Thus, it
might be hoped that the side effects would be tolerable.
Tasmuth [5] reported on a trial in 2002 of venlafaxine HCl following breast
cancer treatment (he participated in the 1996 trial of amitriptyline). In a
10-week study, he used 18.75 mg tablets (half the standard tablet). He also
increased the dose by 1 tablet a week. Although he used a variety of
different pain assessments, his results showed that there was a significant
palliative effect due to the Effexor. Two of his group of 13 did not respond
to the palliation.
Although Tasmuth used twice the dose that I used, I would not recommend
using any more of the drug than necessary to achieve palliation. The larger
the dose, the greater the likelihood of experiencing undesirable side
effects.
Whether or not Effexor is a permanent fix for PN is not known. However, Li
[6] reported that these depressants cause an increase in the output of
neuroprotective genes. The drugs caused an in vitro increase in the mRNA
that leads to the production of the neuroprotective enzyme superoxide
dismutase. Does this mean that Effexor plays a preventive role, or even a
curative role?
There is a serendipitous benefit for some in the use of
Effexor. Quella [7] reported a trial in which the drug reduced the hot
flashes of men undergoing androgen blockade. For 4 weeks 16 men were given
12.5 mg Effexor twice a day. On a subjective assessment, 63% of the men
experienced a significant decrease in the effects of hot flashes.
There have also been some studies [8] [9] to determine whether
antidepressants promote or inhibit cancer. The results are unclear. The
studies were done with the tricyclic antidepressants, phenelzine, and
fluoxetine (Prozac), which do not include Effexor. No mention was made of
prostate cancer. Most of the studies were done in the laboratory.
Dosing
Although Tasmuth [5] used 18.75 mg doses, with
increasing increments, my own experience is that half as much is entirely
adequate. It is possible to subdivide either the tablet or the capsule
granules into doses that are 9-10 mg. It is recommended that the doses be
taken twice a day for full coverage.
The PDR [4] recommends a starting dose of 75 mg, with higher doses up to 375
mg/day. DO NOT TAKE THESE LARGE DOSES FOR TREATING PERIPHERAL NEUROPATHY;
THE SIDE EFFECTS CAN BE SEVERE. In my own case, 18-20 mg/day seems to be
entirely adequate for the purpose.
Side Effects
At a dose of 75-150 mg/day, I experienced continuous
nausea, enough to cause me to lie down frequently. I also experienced a
drugged feeling that caused me to sleep an additional four hours a day. Even
then, I felt tired continually. Even though the pain of PN was relieved, I
stopped the drug due to these effects.
At the dose of 9 mg b.i.d., the feeling of nausea was trivial and has
disappeared after 5 days. There is no drugged feeling, but there is a
noticeable antidepressant effect.
The PDR includes a warning that this drug may interact with monoamine
oxidase inhibitors. At the full dose, this drug has a wide range of
potential side effects, led by headache, asthenia (weakness), sweating,
nausea, constipation, somnolence, dry mouth, dizziness, insomnia,
nervousness. At the low dose, I have only experienced a slight nausea, which
has disappeared, and the antidepressant effect.
According to the PDR, the risk of drug-dependence is not serious. However,
it would be good to taper off the usage when stopping.
References
1. Egbunike IG, Chaffee, BJ. Antidepressants in the
management of chronic pain syndromes. Pharmacotherapy 2000; 10(4): 262-70.
2. Kalso E, Tasmuth T, Neuvonen PJ. Amitriptyline effectively relieves
neuropathic pain following treatment of breast cancer. Pain 1996; (64)2:
293-302.
3. Lang E, Hord AH, Denson D. Venlafaxine hydrochloride (Effexor)
relieves thermal hyperalgesia in rats with an experimental
mononeuropathy. Pain 1996; 68(1): 151-55.
4. Effexor. Physicians’ Desk Reference. 2000. Medical Economics Co., Inc.
3232-42.
5. Tasmuth T, Hartel B, Kalso E. Venlafaxine in neuropathic pain
following treatment of breast cancer. European Journal of Pain
2002; 6(1): 17-24.
6. Li XM, Chlan-Fourney J, Juorio AV, Bennett VL, Shrikhande S,
Bowen RC. Journal of Psychiatry Neuroscience 2000; 25(1): 43-7.
7. Quella SK, Loprinzi CL, Sloan J, Novotny P, Perez EA, Burch PA,
Antolak SJ Jr, Pisansky TM. Pilot evaluation of venlafaxine for the
treatment of hot flashes in men undergoing androgen ablation
therapy for prostate cancer. Journal of Urology 1999; 162(1): 98-
102.
8. Steingart AB, Cotterchio M. Do depressants cause, promote, or
inhibit cancers? Journal of Clinical Epidemiology 1995; 48(11):
1407-12.
9. Brandes LJ, Arron RJ, Bogdanovic RP, Tong J, Zaborniak CL, Hogg GR,
WEarrington RC, Fang W, LaBella FS. Stimulation of malignant
growth in rodents by antidepressant drugs at clinically relevant
doses. Cancer Research 1992; 52(13): 3796-800.
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