Advances in the Treatment of RARE BLOOD PRESSURE DISORDERS
A person's blood pressure is continually changing depending on activity, temperature, diet, emotional state, posture, physical state, and medication use. Blood pressure is a measurement of the force applied to the walls of the arteries as the heart pumps blood through the body. It is determined by the force and amount of blood pumped, and the size and flexibility of the arteries. When any of these factors is compromised, disease may occur.
The pulmonary artery is the blood vessel that carries blood from the heart to the lungs to be re-oxygenated. In pulmonary arterial hypertension (PAH) there is continuous high blood pressure in the pulmonary artery. Possible causes of the increased pressure may include tightened muscles within the artery walls, thickened walls of the pulmonary arteries or scar tissue making the arteries narrower. Tiny blood clots may form within the smaller arteries and cause blockages. The heart, as a result, must work harder to supply the body with enough oxygen-rich blood, and over time the heart muscle weakens.
Shortness of breath is the primary symptom of PAH. People with PAH might also experience tiredness, dizziness, chest pain, or a racing pulse. As the disease progresses, energy level decreases, and these symptoms can occur even when resting.24
There are two types of pulmonary hypertension: primary and secondary. Primary pulmonary hypertension is inherited or occurs for no known reason. Secondary pulmonary hypertension is caused by another condition, such as chronic heart or lung disease or blood clots in the lungs.25 According to the American Heart Association, an estimated 500 to 1,000 new cases of pulmonary hypertension are diagnosed each year.26 Although this condition is very rare, four new orphan drugs have been approved to treat it in the last decade.
Patient Perspective: Women with PAH Face Tough Decisions
Helping Blood Get to the Lungs
Epoprostenol was approved in 1995 for treatment of primary pulmonary hypertension. It is an intravenously administered medicine that works by dilating the arteries, which allows more blood to flow through the vessel, and by preventing blood clot formation.27
Bosentan, the first in a new class of medicines called endothelin-receptor antagonists, was approved in 2001 for the treatment of primary pulmonary hypertension to improve exercise ability and to decrease the rate of disease progression. Taken orally twice a day, it works by decreasing the stiffness of the blood vessels as well as widening them to allow blood to flow more easily.28
Treprostinil was approved in 2002 for patients with the New York Heart Association (NYHA) Class II—IV pulmonary arterial hypertension.29 Heart disease patients are classified according to the NYHA classification system, which is based on the capacity of patients with heart diseases to participate in physical activities, with Class IV disease resulting in discomfort with any activity and symptoms of the disease occurring even at rest. In other words, treprostinil treats patients with moderate to severe PAH, those who experience limitations on physical activity as a result of the disease. Administered by continuous infusion, treprostinil works by dilating the arteries and preventing blood clot formation.30
Iloprost is the newest medicine for treatment of pulmonary arterial hypertension and was approved in 2004 for use by patients with NYHA Class III or IV pulmonary arterial hypertension to increase exercise ability and decrease symptoms.31 It is a novel treatment in that it is inhaled by mouth using a special nebulizer. It works by dilating the arteries and prevents blood clot formation.32
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Hypotension is an abnormal condition in which a person's blood pressure is lower than it should be. It causes symptoms such as dizziness or lightheadedness and inadequate blood flow to the heart, brain, and other vital organs. Orthostatic hypotension results from a sudden change in body position, usually from lying down to an upright position.33 This condition affects 156,000 people34 and can be caused by certain medicines, dehydration, or heart failure/attack.35
Drug Makes Standing Up a Safe Activity
Midodrine hydrochloride is used to treat symptomatic orthostatic hypotension. It works by stimulating the blood vessels to tighten, thereby raising blood pressure. Midodrine was approved in 1996 based on its ability to increase one-minute standing systolic blood pressure.36
The Orphan Drug Act was enacted in 1983 and encourages companies to develop and manufacture drugs for rare conditions.
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24 National Heart, Lung, and Blood Institute, What Is Pulmonary Arterial Hypertension?, http://www.nhlbi.nih.gov/health/dci/Diseases/pah/pah_what.html (accessed 12 September 2005).
26 American Heart Association, Primary or Unexplained Pulmonary Hypertension, http://www.americanheart.org/presenter.jhtml?identifier=4752 (accessed 16 May 2005).
27 S. Reents et al., Clinical Pharmacology, Gold Standard Multi-media, Inc., Flolan®, http://cp.gsm.com (accessed 16 May 2005).
28 S. Reents et al., Clinical Pharmacology, Gold Standard Multi-media, Inc., Tracleer®, http://cp.gsm.com (accessed 16 May 2005).
29 S. Reents et al., Clinical Pharmacology, Gold Standard Multi-media, Inc., Remodulin®, http://cp.gsm.com (accessed 16 May 2005).
31 Food and Drug Administration, Patient Information Sheet: Iloprost, http://www.fda.gov/cder/drug/InfoSheets/patient/iloprostPIS.htm (accessed 12 September 2005).
32 S. Reents et al., Clinical Pharmacology, Gold Standard Multi-media, Inc., Ventavis®, http://cp.gsm.com (accessed 16 May 2005).
33 National Library of Medicine, MedlinePlus Medical Encyclopedia, Hypotension, http://www.nlm.nih.gov/medlineplus/ency/article/003083.htm (accessed 12 September 2005).
34 Food and Drug Administration, Office of Orphan Products Development (OOPD), Approved Orphan Drug Spreadsheet, available upon request from OOPD.
35 National Library of Medicine, MedlinePlus Medical Encyclopedia, Hypotension, op. cit.
36 S. Reents et al., Clinical Pharmacology, Gold Standard Multi-media, Inc., Midodrine, http://cp.gsm.com (accessed 3 August 2005).
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