The primary objective of the study was to evaluate the effect of Nerispirdine (50 mg or 400 mg) and placebo given orally as a single dose once a week in crossover design on latency of Visual Evoked Potentials (VEP) P100 in optic nerves.

Secondary objectives included evaluation of the effect of Nerispirdine on VEP amplitude and other visual parameters including visual acuity and contrast, as well as evaluation of the safety and tolerability of Nerispirdine in patients with Multiple Sclerosis (MS).

Contrast sensitivity and visual acuity examinations (in addition to Optical Coherence Tomography [OCT] and VEPs) were needed during the screening period for defining etiologic relationships (if non-MS related impairment) and for assessing the effect of treatment of age-related eye disease versus the MS-related vision impairment.

The crossover design included 3 treatment periods 1 week apart and 6 treatment sequences. Study participation were to be 5 weeks.

Inclusion Criteria:

• Clinically definite MS (McDonald criteria), which includes patients with remitting-relapsing, secondary progressive, progressive-relapsing, or primary progressive MS who have had a past history of Optic Neuritis.

Exclusion Criteria:

• Multiple sclerosis exacerbation within 60 days of the Screening Visit and the relapse involved the visual fields or visual acuity
• No eye with appropriate degree of lesions for this study as defined by criteria based on degree of visual acuity deficit, refractive error, VEP P100 latency and average retinal nerve fiber layer thickness of as measured by Optical Coherence Tomography (OCT)
• Any MS-unrelated prior ophthalmological impairment (eg, compressive, ischemic, toxic, or nutritional optic neuropathies, Leber's hereditary optic atrophy)
• Previously exposed to 3,4-diaminopyridine or 4-aminopyridine

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.