Combination therapy with bosentan and phosphodiesterase-5 inhibitor in pulmonary arterial hypertension

To the Editors:

Hoeper et al. 1 have produced an interesting report of their clinical experience of combined therapy with bosentan and sildenafil in patients with idiopathic pulmonary arterial hypertension. Whilst it is true that the relatively scant literature supporting the use of phosphodiesterase-5 inhibitors is centred around sildenafil, its relatively short duration of action requires the use of a thrice-daily regime. This has significant implications for compliance and, since treatment is continual, has large implications in the cost of treatment. It would be more logical to use a long-acting phosphodiesterase-5 inhibitor, and, with the advent of tadalafil, once-daily treatment becomes possible.

Here, we report our experience with a combination of bosentan and tadalafil in a 42-yr-old male with idiopathic pulmonary hypertension who had documented poor compliance with nebulised iloprost. Sildenafil 25 mg t.d.s. was added to bosentan, following a clinical deterioration and the finding of an estimated pulmonary artery systolic pressure of 130 mmHg, and this caused a fall in pulmonary artery pressure to 50 mmHg. Treatment with sildenafil was stopped 1 month later at another centre, and the pulmonary artery systolic pressure increased to 100 mmHg. Subsequently, sildenafil was restarted in combination with bosentan, and exercise tolerance doubled. After 3 months of combination treatment, the issue of compliance was raised by the patient and it was decided to substitute tadalafil 20 mg once daily for the sildenafil. The patient has continued on tadalafil for 9 months with an excellent symptomatic response. The last estimated pulmonary artery pressure was 61 mmHg.