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Source: J Am Coll Cardiol | Posted 12 years ago

Sildenafil Citrate (Viagra) Increases Brain Blood Flow in MS Patients and Could Treat Cognitive Impairment Associated With the Disease

By Bruce Sylvester

THESSALONIKI, GREECE — October 3, 2005 — Sildenafil citrate (Viagra) appears to help cerebral blood perfusion and brain activation in patients with secondary progressive multiple sclerosis (MS), researchers reported here on September 29[ ]th[ ] at the 21[ ]st[ ] Congress of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS).

“Sildenafil it could become a treatment for the cognitive impairment which affects more than 50% of MS patients,” said investigator and presenter Stephanie Manson, MD, researcher, Resonance Imaging Brain Center, University of Oxford, Oxford, United Kingdom.

“MS patients have reduced cerebral flow as part of the onset of the disease. This starts at a very early stage of the disease,” Dr. Manson said. “We took secondary progressive patients and we gave them 1 dose of Viagra. We found that it acutely increased their cerebral blood flow, which means that the neurons are getting more oxygen. It is quite dangerous to have a low cerebral blood flow.”

Explaining the reasoning behind the study, the researchers wrote that sildenafil citrate is a potent and specific inhibitor of phosphodiesterase type 5, and inhibition of it causes vasodilatation only in the presence of elevated nitric oxide. Multiple sclerosis patients show reduction of cerebral blood flow, particularly in the grey matter of the brain, which is believed to be linked with cognitive dysfunction. Due to elevated levels of the nitric oxide precursor inducible nitric oxide synthase (iNOS) in the multiple sclerosis brain, the researchers hypothesised that sildenafil might increase cerebral blood flow in MS patients.

For their study, the investigators enrolled 6 patients with secondary progressive MS and 5 healthy controls, in addition to 7 diabetic patients, who were also scanned to determine if the effects of sildenafil were disease specific. All of the subjects were men, and all received sildenafil as a treatment for erectile dysfunction.

The subjects underwent functional magnetic resonance imaging (fMRI) immediately prior to taking sildenafil and again 1 hour after dosing. During each scan, a perfusion arterial spin labeling (PASL) scan was taken using a method that quantifies resting cerebral blood flow for both pre- and postsildenafil administration. FMRI was also performed to evaluate visual activation, pre- and postsildenafil.

Results show that after treatment with sildenafil the MS patients achieved a 33% +/= 29% increase in grey matter perfusion (P = .03) and a 22% +/= 14% increase in white matter perfusion (P = .01), and that neither diabetic subjects nor healthy controls had a significant change in perfusion.

The scans showed no significant difference in centers of activation between MS patients, diabetics, and healthy controls, either before or after drug administration.

However, MS patients had a significant decrease in activation after sildenafil dosing compared with baseline, particularly in areas of visual association in the parietal lobe, the investigators reported.

Dr. Manson added, “So the implication of the finding is that Viagra could prove to be neuroprotective for MS patients. This was a small study with large implications and, clearly, more research is called for on this subject. Next, we want to study for the safety and efficacy of chronic dosing of Viagra for MS patients.”

[Presentation title: Effect of Sildenafil Citrate on CBF and BOLD Activation in Multiple Sclerosis Patients. Poster 237]

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