A new type of drug which increases blood flow to the vagina in animal
experiments has now been shown to be safe in rats. Derived from an
experimental heart drug, the new compounds could one day help treat
women who find it difficult or impossible to become sexually aroused,
say researchers at the drugs company Pfizer.
Previous tests have shown that the new compounds, including the most
potent one, called R-13, increased vaginal blood flow in animals. New
tests now demonstrate that the drugs are safely tolerated by rats.
The ultimate aim is to address female sexual arousal disorder (FSAD)
in women. The condition sometimes involves blood flow problems in the
pelvic region, which might be restored by a drug intervention.
Experts agree the approach might eventually benefit the small subset
of women who suffer sexual dysfunction due to a physiological cause,
due to nerve damage in the pelvic area from surgery, for example. But
they stress that such drugs would not effectively treat FSAD when it
is due to purely psychological factors.
In fact, some question the very existence of FSAD, adding that some
women's sexual dissatisfaction may have to do with the nature of the
relationship the women are in (see Caution over sexual arousal patch
for women).
Sex differences
In the late 1990s, the approval of the drug sildenafil (Viagra) made
by Pfizer, popularised the idea that men could be treated for erectile
dysfunction with a simple pill. It became one of the pharmaceutical
giant's best-selling drugs.
Drug companies' search for a compound to treat sexual dysfunction in
women, however, are complicated by the fact that the disorder appears
to have a wider number of causes in women, suggests Lori Brotto at the
University of British Columbia in Vancouver, Canada.
Researchers at Pfizer derived the new compounds from a drug called
Candoxatrilat, which was tested in clinical trials during the 1990s
for treating chronic heart failure.
Tests show that a precursor of Candoxatrilat appears to disable a key
enzyme called neutral endopeptidase, or NEP. This is important because
NEP usually degrades a hormone called vasoactive intestinal peptide
that promotes blood flow to the vagina. So blocking NEP may allow the
hormone to maintain this blood flow.
"Too early"
The Pfizer group found that rats can tolerate NEP inhibitors derived
from Candoxatrilat, such as a newly designed compound, R-13. New
research carried out by the team also shows that R-13 rapidly
inactivates NEP when ingested by laboratory animals. They add that
previous experiments have suggested that R-13 can somewhat increase
vaginal blood flow in rabbits.
"The objective of the research is to identify a rapid-acting,
efficacious and well tolerated compound," says Joel Morris, a
spokesman for Pfizer in Sandwich, Kent, UK.
"A small subgroup of women might benefit from a biological approach,"
says Brotto, who studies FSAD. But she adds that because there is such
limited testing of the compound in animals, let alone humans, "it's
far too early to conclude anything" about the compound's potential to
treat sexual dysfunction in women.
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# posted by Network @ 4:05 AM
