Post-Polio Health ISSN 1066-5331)
Vol. 14, No. 1, Winter 1998
Pyridostigmine was not found to provide significant benefits with respect to quality of life, fatigue, or isometric muscle strength compared with placebo, although a trend was noted towards increased strength in very weak muscles.
The North American Post-Poliomyelitis Pyridostigmine Study (NAPPS) received support from ICN Pharmaceuticals, the company that markets and distributes pyridostigmine as Mestinon. Currently approved for the treatment of myasthenia gravis, Mestinon is an oral anticholinesterase agent which improves the transmission of impulses across the neuromuscular junction, the interface of nerve and muscle cells.
NAPPS was initiated by participating investigators in five medical centers in the United States and Canada:
Neil R. Cashman, MD and Daria A. Trojan, MD, Montreal Neurological Institute and Hospital, Montreal, Quebec, Canada;
Burk Jubelt, MD, SUNY Health Science Center, Syracuse, New York;
James Agre, MD, PhD, University of Wisconsin at Madison;
Theodore L. Munsat, MD and Dave Hollander, MD, New England Medical Center, Boston, Massachusetts;
and Robert Miller, MD, California Pacific Medical Center, San Francisco.
Conducted during 1996-97, NAPPS was a double-blind, randomized, placebo-controlled trial that followed 126 patients given either 60 mg of pyridostigmine three times daily or placebo for six months; 64 received pyridostigmine and 62 received placebo. All participants completed the study.
During the six-month course of the study, 70 percent of patients on pyridostigmine and 73 percent of patients on placebo had at least eighty percent compliance with the medication. The study medication was well tolerated: four severe adverse events were observed during the trial, three of which occurred in pyridostigmine-treated patients. Some relative contraindications to pyridostigmine include certain cardiac arrhythmias, increased bronchial secretions and reactivity, and some urological disorders.
The study did not show a difference between pyridostigmine and placebo patients in terms of their health-related quality of life, fatigue, (as measured by two fatigue scales), and most measures of isometric muscle strength.
Health-related quality of life was assessed with the short form health survey – 36 (SF-36). Fatigue was measured with two subjective fatigue scales: the fatigue severity scale and the Hare fatigue symptom scale. Muscle strength was measured as isometric strength in twelve muscle groups in each patient by a modified Tufts quantitative neuromuscular exam.
Dr. Trojan, who presented at the annual meeting of the American Academy of Physical Medicine and Rehabilitation (AAPM&R) in Atlanta in November, noted that there was a non-significant increase in strength in very weak muscles (1% to 25% of predicted normal strength) in pyridostigmine-treated patients at six months of treatment.
Dr. Trojan also commented that the results were unexpected and did not reflect the investigators' clinical impression that there appeared to be a clear benefit in some patients.
Another purpose of the study was to assess the effect of Mestinon on IGF-1 (insulin-like growth factor-1) which is believed to support the sprouting of motor neurons. IGF-1 is known to decrease with age and may be a contributing factor to the onset of post-polio syndrome.
IGF-I serum analyses have not yet been completed. Data analysis for the trial is still ongoing. The open trial phase of the study is still in progress. Therefore, this is not "the last word" on the study. We expect the NAPPS trial to be submitted for publication in the next few months.
ICN Pharmaceuticals has no plans to fund further research into the use of Mestinon for post-polio fatigue. During these few years of affiliation, considerable literature aimed at educating health professionals has been created under the auspices of the Post-Polio Task Force, supported by an unrestricted educational grant from ICN Pharmaceuticals.