Cialis, a drug marketed to treat erectile dysfunction and benign prostatic hyperplasia in men, is also effective in treating pulmonary hypertension. A number of studies have investigated the uses for phosphodiesterase-5 (PDE5) inhibitors beyond the treatment of erectile dysfunction. Pulmonary hypertension is an ideal disease candidate for such studies as the smooth muscle cells of the lungs also produce PDE5.
Pulmonary Hypertension
Pulmonary hypertension is a progressive and chronic condition that usually arises out of an underlying disease such as chronic lung or heart disease. It involves the vasoconstriction of the blood vessels within the lungs, which increases the pressure at which the blood flows through. Over time, the increased blood pressure causes fibrosis or thickening in those vessels, which further impairs blood flow and increases blood pressure. Extremely high blood pressure in the lung vasculature results in difficulty in breathing and shortness of breath, fatigue, peripheral edema or swelling of the extremities, dizziness and fainting.
Patients with pulmonary hypertension exhibit a marked decrease in exercise tolerance that inhibits daily activities. However, because the disease presents slowly, they may experience symptoms such as a non-productive cough, fatigue and dizziness, peripheral edema and chest pain for years before seeking consultation with a physician. Pulmonary hypertension can lead to heart failure, and can result in death within three years of diagnosis without active medical intervention. Pulmonary hypertension is found in 60% of patients with scleroderma, up to 21% of patients with rheumatoid arthritis, 14% of patients with systemic lupus erythematosus, from 20% to 40% of patients with sickle cell disease and more rarely at 0.05% in patients with HIV(2).
Treatment
There are five categories of pulmonary hypertension, and type will determine complete treatment protocol. Pulmonary venous hypertension or congestive heart failure is treated through diuretics, beta-adrenergic blocking agents, angiotensin-converting-enzyme inhibitors, or surgical repair or replacement of the mitral or aortic valve. Lifestyle changes are also recommended, such as increased exercise and lower salt intake to complement diuretics. Patients with pulmonary arterial hypertension will also be treated with diuretics, but not with other PVH drugs; rather, digoxin, anticoagulants and oxygen therapy will be used.
Use of PDE5 Inhibitors to Treat Pulmonary Hypertension
Recent scientific research has focused on using PDE5 inhibitors in pulmonary arterial hypertension because the smooth muscle cells of the lungs are similar in pathology to erectile tissue in that they also produce phosphodiesterase-5. Two related studies conducted by the Pulmonary Arterial Hypertension and Response to Tadalafil (PHIRST) Study Group using Tadafil (generic Cialis) are worth noting as they report significant potential as treatment possibilities.
As reported in Circulation, the journal of the American Heart Association, in 2009 the PHIRST Study Group released its findings of a 16 week, double-blind, placebo-controlled study to investigate the efficacy of treating pulmonary hypertension with Tadalafil, the generic equivalent of Cialis. Four hundred and fifty patients with pulmonary hypertension participated in the study, and were randomly placed in either the group receiving a placebo or the group receiving Tadalafil. Significant findings of this study included improvements in exercise capacity, decreased incidence of clinical worsening, and an improvement in the quality of life for patients. Inhibition of clinical deterioration, improved exercise abilities and a better quality of life were particularly marked in the patients receiving a daily Tadalafil dose of 40 mg (1).
The PHIRST Study group conducted a second 52-week, double-blind, uncontrolled extension study using participants from the first 16-week study with the objective of evaluating the efficacy, safety and durability of using Tadalafil for the treatment of pulmonary arterial hypertension. The study found that, similar to the shorter investigation, long-term treatment with Tadalafil was well tolerated by patients, and produced the same improvements in exercise tolerance and quality of life. There were also fewer clinical deteriorations among patients on either a 20 mg or a 40 mg daily dosage.(3)
In October 2008, U.S. News and World Report informed the world of the expanded possibilities of Cialis in treating pulmonary hypertension. “This new study of Cialis, taken once daily, demonstrates that the drug substantially improves functional capacity, improves quality of life, and also results in less clinical worsening in patients with pulmonary arterial hypertension.”(3) Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, noted that “These are impressive findings….Tadalafil represents a very promising new therapy for patients with pulmonary arterial hypertension, that may be used alone or in combination with other treatments such as bosentan.’ ”(4)
Sources
(1) http://circ.ahajournals.org/content/119/22/2894.full, retrieved 3/4/2014. (2) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1745964/, retrieved 3/4/2014. (3) http://www.ncbi.nlm.nih.gov/pubmed/22818063, retrieved 3/4/2014 (4) http://health.usnews.com/health-news/family-health/heart/articles/2008/10/28/cialis-may-help-ease-pulmonary-hypertension, retrieved 3/4/2014.
