Viagra (sildenafil citrate)


Other name: Sildenafil citrate

Sildenafil citrate is a treatment for erectile dysfunction, a symptom that can affect men with multiple sclerosis.

Viagra was the first drug to become available as a treatment for erectile dysfunction, being licensed in 1998. Originally tested as a treatment for heart problems, it has also been used in treating high blood pressure (under the name Revatio) and altitude sickness.

Generic sildenafil can be prescribed without restriction by a GP to anyone with erectile dysfunction. A version called Viagra Connect can also be ordered from high street pharmacies without a prescription, though you will need to talk to a pharmacist to make sure this is an appropriate drug for your symptoms.

How do I take sildenafil?

Sildenafil is taken about 30 minutes to an hour before sexual activity and the effects last for about four hours. It will take longer for the drug to take effect if taken after eating fatty foods. The maximum dose frequency is once a day.

Side effects and contraindications

Common side effects include headaches, flushing, upset stomach, visual disorders, nasal congestion and dizziness.

You should not take sildenafil if you:

  • are receiving treatment with drugs containing nitrates, such as are used to treat angina or are using recreational drugs such as poppers 
  • have serious heart disease
  • have low blood pressure or uncontrolled high blood pressure.

If you have problems with liver or kidney function, talk to your doctor before starting treatment with sildenafil.

Studies have shown that sildenafil is not effective in treating women with sexual dysfunction in MS.

How sildenafil citrate works

Erectile dysfuntion is the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. In multiple sclerosis this is commonly associated with bladder symptoms and both disorders are believed to be as a direct result of damage to the nerves in the spinal cord.

Sildenafil works by delaying the action of enzymes called PDE5 (phosphodiesterase type 5), which regulate blood flow in the penis. Altering levels of this enzyme means that normal sexual stimulation leads to better erections.

Find out more

References
Fowler CJ, et al.
A double blind, randomised study of sildenafil citrate for erectile dysfunction in men with multiple sclerosis.
Journal of Neurology, Neurosurgery and Psychiatry 2005;76(5):700-705.
Full article (link is external)
Safarinejad MR.
Evaluation of the safety and efficacy of sildenafil citrate for erectile dysfunction in men with multiple sclerosis: a double-blind, placebo controlled, randomized study.
Journal of Urology 2009;181(1):252-258.
Summary (link is external)
Xiao Y, et al.
Sildenafil citrate for erectile dysfunction in patients with multiple sclerosis.
Cochrane Database Systematic Reviews 2012 Apr 18;4:CD009427.
Full article (link is external)
On this page