Volibris is a medicine that contains the active substance ambrisentan. It is available as tablets (pale pink, square: 5 mg; deep pink, oval: 10 mg).
|Table of Contents|
|What is it used for?|
|How is it used?|
|How does it work?|
|How has it been studied?|
|What benefits has it shown during the studies?|
|What is the risk associated?|
|Why has it been approved?|
Volibris is used to treat patients with pulmonary arterial hypertension (PAH) to improve exercise capacity (the ability to carry out physical activity). PAH is abnormally high blood pressure in the arteries of the lungs. Volibris is used in patients with class II or III disease. The ?class? reflects the seriousness of the disease: ?class II? involves slight limitation of physical activity and ?class III? involves marked limitation of physical activity. Volibris has been shown to be effective in PAH with no identified cause and in PAH caused by connective tissue disease.
Because the number of patients with PAH is low, the disease is considered ?rare?, and Volibris was designated an ?orphan medicine? (a medicine used in rare diseases) on 11 April 2005. The medicine can only be obtained with a prescription.
Treatment with Volibris must be started by a doctor who has experience in the treatment of PAH. The standard dose of Volibris is 5 mg once a day. The tablets should be swallowed whole. A 10 mg dose may have a greater effect in patients with class III disease but this is associated with an increased risk of fluid retention and swelling. Patients with PAH caused by connective tissue disease may also need to take 10 mg to get the best benefit from Volibris. The dose should only be increased if the 5 mg dose is well tolerated. Patients also taking ciclosporin (a medicine that reduces the activity of the immune system) should not take more than 5 mg Volibris a day and should be closely monitored by their doctor.
PAH is a debilitating disease where there is severe constriction (narrowing) of the blood vessels of the lungs. It causes high blood pressure in the vessels taking blood from the heart to the lungs. This pressure reduces the amount of oxygen that can get into the blood in the lungs, making physical activity more difficult. The active substance in Volibris, ambrisentan, blocks the receptors for a hormone called endothelin, which causes blood vessels to constrict. By blocking the effect of endothelin, Volibris allows the vessels to dilate (expand), helping to lower the blood pressure and improving symptoms.
Various doses of Volibris (2.5, 5 and 10 mg) have been compared with placebo (a dummy treatment) in two main studies involving a total of 394 patients with PAH, most of whom had class II or III disease that was of unknown cause or caused by connective tissue disease. The main measure of effectiveness was the change in the distance the patients could walk in six minutes after 12 weeks of treatment. This is a way of measuring the change in exercise capacity.
Volibris was more effective than placebo at improving exercise capacity in patients with class II or III disease. Overall, in the two studies taken together, the patients could walk an average of around 345 m in six minutes at the start of the study. The patients taking 5 mg Volibris once a day could walk an average of 36 m further after 12 weeks of treatment, and the patients taking placebo showed a reduction of 9 m. Patients with class III disease and those with PAH caused by connective tissue disease gained a greater benefit from the 10-mg dose than from the 5-mg dose.
The most common side effects with Volibris (seen in more than 1 patient in 10) are headache (including sinus headache and migraine), peripheral oedema (swelling, especially of the ankles and feet) and fluid retention. For the full list of all side effects reported with Volibris, see the Package Leaflet.
Volibris should not be used in people who may be hypersensitive (allergic) to soya, ambrisentan or any of the other ingredients. Because it might be able to cause birth defects, Volibris must not be used in pregnant women or in women who could become pregnant unless they are using reliable contraception. It must not be used in patients who are breast-feeding, who have severe liver problems or who have high levels of liver enzymes in the blood.