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news.Pfizer's blockbuster impotence drug Viagra could effectively treat a chronic heart condition, according to a study conducted by researchers at the John Hopkins University.
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Viagra (sildenafil citrate), which was originally intended to be a heart medication, was found to effectively treat enlarged hearts in mice, stopping further muscle growth from occurring and reversing existing growth, including the cellular and functional damage it created.
Sildenafil became the focus of the research because it blocks or stops an enzyme, called phosphodiesterase 5 (PDE5A), involved in the breakdown of a key molecule, cyclic GMP, which serves as a “natural brake” to stresses and overgrowth in the heart. PDE5A is also the biological pathway blocked in the penis to prevent the relaxation of blood vessels and maintain erections.
The findings are the first to show that sildenafil is an effective treatment for a chronic heart condition. It is also the first study to reveal that the enzyme pathway blocked by sildenafil (PDE5A), never before known to play a significant role in the heart, is active when the heart is exposed to pressure stress and hypertrophied.
The results provide some of the strongest evidence to date that blocking the heart’s adaptive response to hypertrophy does not harm its function but, in fact, may improve it, Dr David Kass, the study’s senior author, said.
Plans are now underway by the researchers for a multicenter trial to test if sildenafil has the same effects on hypertrophy in humans.
“This study shows that sildenafil can make hypertrophy go away,” said Kass. “Its effects can be both stopped in their tracks and reversed. Overall, the results provide a better understanding of the biological pathways involved in hypertrophy and heart dilation, leading contributors to heart failure.”
Kass continued, “They suggest possible therapies in the future, including sildenafil, which has the added benefit of already being studied as safe and effective for another medical condition.”
Cardiac hypertrophy commonly develops from high blood pressure, which forces the heart to pump harder to circulate blood throughout the body. According to the latest statistics from the American Heart Association, in 2002, 65 million Americans have high blood pressure. Patients that develop hypertrophy have two to three times the risk of suffering cardiovascular disease, including heart failure and sudden cardiac death.