The goal of this observational study is to compare the impact of an antipyretic, acetaminophen to a placebo on gait fatigue in persons with multiple sclerosis (MS). The primary question this study is asking is the following: will the antipyretic effects of acetaminophen result in less gait fatigue in persons with MS? Participants will be asked to come for two sessions over a 1 week period. In the first week, subjects will be blind-randomized into either the acetaminophen or placebo group. They will then undergo a test to determine their gait speed by performing two 25 foot walks at their best comfortable pace. The walks will be 1 minute apart. The average speed from those 2 walks will be obtained. Subjects will then take either the acetaminophen or the placebo. Following a 45 minute rest period they will then get on a treadmill and will walk at the previously determined speed for as long as they can. Walking will stop if the subject can no longer maintain the speed or if they wish to no longer continue. The subjects will wear a safety harness at all times during the walk to prevent falls. Heart rate and core body temperature will be measured via skin sensors. One week later the subjects will return and repeat the procedure but this time in the opposite condition. Subjects who took the acetaminophen will take the placebo and subjects who took the placebo will take the acetaminophen. The difference between distance walked in the 2 conditions will be compared.

Persons with Multiple Sclerosis have difficulty with walking longer distances because of fatigue. The fatigue is in large part a result of heat sensitivity; during exercise the increase in metabolism results in increases in core temperature which reduces conduction through demyelinated nerves.

Medications such as Acetaminophen are antipyretic which are used to reduce temperature in persons with a fever. Antipyretics may therefore result in lowering the temperature in persons with MS and allow them to walk longer distances.

In this study, ambulatory persons with MS will be randomly assigned to receive either acetaminophen or a placebo. Participants will be blinded to which they receive. They will then perform a 25 foot walk test where they will be asked to walk 25 feet at their best comfortable speed. The walks will be 1 minute apart. The average speed of the 2 walks will be obtained. Subjects will then receive either the acetaminophen or the placebo and rest for 45 minutes so that the medication can reach peak effect, and then will walk on a treadmill at the previously obtained speed until they can no longer maintain the original speed, or they wish to stop. One week later subjects will return and take whichever pill they did not take the first time.

We hypothesize that subjects who take the antipyretic will walk for a longer period than those who took the placebo. If our hypothesis is correct, it will suggest that antipyretics should be further investigated as a means of addressing thermosensitivy leading to gait fatigue in persons with MS

Inclusion Criteria:

• A definitive MS diagnosis confirmed by self-report,
• The ability to walk for 2 minutes continuously with or without assistive device ---Age 18-65
• Provide a blood test within the last 6 months to 1 year reflecting normal liver and renal profile (normal liver enzymes and normal creatinine level).

Exclusion Criteria:

• Any current or recent exacerbations
• Any adverse reaction to antipyretics
• Recent use of steroids
• Any non-MS conditions that interfere with walking performance.

ambulatory persons with MS

all de-identified data will be shared upon request

for 7 years following termination of data collection