Viagra approved in Canada for Treatment
of Erectile Dysfunction
Medical Update Memo
March 9, 1999
Pfizer Canada announced on March 9 that the federal Health
Protection Branch has approved the oral therapy Viagra (sildenafil
citrate) for the treatment of erectile dysfunction. It is anticipated
that the therapy will be available by prescription at the end
of March. Erectile dysfunction can occur as the result of multiple
On March 9, Pfizer Canada announced that the federal Health
Protection Branch has approved the use in Canada of Viagra (sildenafil
citrate), a new type of medication for erectile dysfunction
(ED). In large Phase III clinical trials involving more than
4,500 men with ED, the drug was found to be effective as a treatment
for ED in about 70 percent of the treated group compared to
placebo. Participants were diagnosed as having mild, moderate
or complete ED because of a broad range of medical conditions
including high blood pressure, high cholesterol levels, spinal
cord injury, diabetes and prostate surgery. The median age was
55, and participants had experienced ED for an average of five
years prior to the trials.
Erectile dysfunction is defined as the consistent
inability to achieve and/or maintain an erection sufficient
for satisfactory sexual activity. It is associated with a broad
range of medical conditions including multiple sclerosis, diabetes,
prostate cancer surgery, spinal cord injury, cardiovascular
diseases and depression.
Viagra works by increasing the blood flow
to the penis which is necessary for establishing and maintaining
an erection. The drug is the first in a new class of medications
known as phosphodieterase type 5 inhibitors. It is taken orally
as a single tablet in three different choices of dosage strength
about 30 minutes to one hour before anticipated sexual activity.
Although the original clinical trial did
not include men with multiple sclerosis, clinical trials of
Viagra's safety and efficacy in men with MS are now underway
in the United States and Europe. Results are anticipated sometime
Erectile dysfunction is the most commonly
reported sexual concern of men with multiple sclerosis. Some
studies suggest that up to 70 percent of men with MS experience
ED at some point in the disease.
Viagra should not be taken by individuals
who are taking any form of nitrates, including the heart medicine
nitroglycerine. The combined use of nitrates and Viagra may
lead to sudden and potentially dangerous drops in blood pressure.
During the clinical trial, the most common side effects of taking
Viagra were headache, facial flushing and indigestion.
As with other treatments which can benefit
people with MS, the Multiple Sclerosis Society of Canada will
be urging provincial governments as well as private and group
health insurance payers to provide coverage for this new drug.
The Multiple Sclerosis Society of Canada is an independent,
voluntary health agency and does not approve, endorse or recommend
any specific product or therapy but provides information to
assist individuals in making their own decisions.