Flolan (epoprostenol) is a therapy manufactured by GlaxoSmithKline and approved by the U.S. Food and Drug Administration for patients with pulmonary arterial hypertension (PAH).

It is also being used to treat patients with PAH associated with systemic scleroderma.

How Flolan works

Scleroderma is a rare disease characterized by the scarring and thickening of the connective tissue in the skin and, in more severe cases, the internal organs. As the disease progresses, the thickening of the connective tissue around the blood vessels results in poor blood flow and can lead to PAH.

Flolan is a synthetic analog of prostacyclin, a natural hormone produced by cells in the walls of blood vessels. This hormone activates signaling pathways that cause blood vessels to relax and widen. It also prevents blood cells called platelets from clumping together and blocking the blood vessels.

Flolan, therefore, works by relaxing blood vessels and facilitating blood supply from the heart to the lungs reducing the workload of the heart and improving patients’ ability to be physically active.

Flolan in clinical trials for scleroderma-associated PAH

The short- and long-term effects of epoprostenol directly injected into the bloodstream in patients with systemic scleroderma-associated PAH were first evaluated in a clinical trial conducted in 1999.

During the study, 16 patients received epoprostenol in increasing doses to determine the best dose. Of these patients, 13 continued to receive epoprostenol after being discharged, and their symptoms, exercise tolerance, and resistance in the blood vessels of their lungs were measured.

Results, published in the journal Arthritis & Rheumatology, showed that epoprostenol treatment led to a reduction in the resistance in the blood vessels of their lungs by 25 percent or more. Patients’ symptoms and exercise capacity also improved.

Another trial investigated the effect of epoprostenol in 111 patients with moderate to severe PAH due to scleroderma. During the trial, patients received epoprostenol plus conventional therapy or conventional therapy alone for 12 weeks. Results, published in the journal Annals of Internal Medicine, showed that epoprostenol treatment was associated with significant improvements in exercise capacity and hemodynamic parameters such as heart rate and blood pressure at 12 weeks compared with conventional therapy alone. Data from a three-year extension period of this study showed improved survival in patients receiving epoprostenol compared with controls from previous studies.

The effect of epoprostenol on the survival of 102 patients with scleroderma-associated PAH was evaluated in an open-label, three-year extension trial following an initial, randomized, controlled, 12-week trial. Researchers also collected information about adverse events and dosing throughout the study.

Results of these studies, published in The Journal of Rheumatology, showed that the probabilities of survival during the first two years for the patients treated with epoprostenol were 71 percent during the initial study and 52 percent in the extension study. This measure remained constant at 48 percent during the third and fourth years following diagnosis. These results were better than other studies that had an approximately 50 percent survival rate at one year following a diagnosis of PAH associated with scleroderma.

Other details

The most common side effects of epoprostenol include dizziness, jaw pain, headache, muscle or bone pain, nausea, and vomiting.

To overcome handling limitations of Flolan, Actelion Pharmaceuticals developed a new formulation of epoprostenol called Veletri. Veletri requires less frequent mixing than Flolan and does not need to be stored in cold temperatures.

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