Neurotoxic Medications and Worsening of Neuropathy

[Guest guest]

Neurotoxic Medications and Worsening of Neuropathy

The CMTA also has a " Medical Alert " list of potentially neurotoxic

medications. The list is published on the web at http://www.charcot-

marie-tooth.org/med_alert.php

Neurologists Louis H. Weimer of Columbia University and Podwall

of the Albert Einstein College of medicine, however, note that

while " existing peripheral neuropathy is a generally accepted risk

factor for increased susceptibily to neurotoxic agents, " there is

some question whether CMT patients should avoid neurotoxic

medications even when their use is clearly indicated. The extensive

distribution of the list raises the additional concern that, in some

cases, an inordinate degree of perceived risk could deter the use of

a preferred medication for a condition unrelated to CMT.

Weimer and Podwall conducted an extensive literature search and and

found that 22 of 26 reports of neurotoxicity in CMT patients

concerned vincristine, a chemotherapeutic agent (listed on Medical

Alert as " definite high risk " ). The remainder concerned nucleoside

analogs and taxoids (which fall in the " moderate to significant risk "

category).

They also reviewed data from the CMT North American Database,* a

computerized registry of clinical details of CMT patients in the U.S.

and Canada. The database provided 996 drug entries of 209 persons

from 190 families. Medications with multiple reported exposures and

more than one claim of symptomatic worsening of neuropathy included

metronidazole, nitrous oxide, statins, nitrofurantoin, phenytoin, and

sertraline. Others (isoniazid, penicillin — high IV doses) had 1 or 2

adverse reports. Still other agents were notable for exposures

without reported neuropathic effect. These included adriamycin,

chloramphenicol, dapsone, disulfiram, hydralazine, lithium, and

pyridoxine.

Overall, Weimer and Podwall conclude that treatment with vincristine

poses an " unacceptable risk to patients with known or possible

CMT1A. " They further conclude that the use of other agents in the

significant risk category of the list should be considered with

caution, and " the probable lesser risk of agents in lower categories

should also be weighed when prescribing these drugs for people with

CMT. "

At the same time, however, Weimer and Podwall are careful to point

out that these conclusions are based on limited direct evidence, and

that there are several possible explanations for the lack of

documentation in the literature regarding adverse effects of many of

the drugs on the CMTA neurotoxic drug list.

In particular, cases of worsening of neuropathy may by unreported or

unrecognized, so it is still prudent to make your treating physician

aware that drugs on the Medical Alert list may have the potential to

adversely affect someone with CMT and to discuss alternative

medications. More importantly, if you begin taking any of the

medications on the list, or any other medication, and you notice a

change in your condition, you should notify your physician

immediately.

More information at

http://www.charcot-marie-tooth.org/archives/cmt_headlines_story.php?

id=26

*The CMT North Ameican Database was initiated at Wayne State

University. Funded by the CMTA and the MDA, it is currently

maintained in the Department of Medical and Molecular Genetics at

Indiana University.