Background: Sildenafil was the only phosphodiesterase-5 inhibitor available for the treatment of pulmonary arterial hypertension (PAH) until the approval and availability of once-daily tadalafil. Since no direct comparative study is likely to be performed between these agents, we sought to evaluate the feasibility of transitioning stable PAH patients from sildenafil to tadalafil.
Methods: The primary end point was continuation on tadalafil without clinical deterioration. A functional outcome through an evaluation of serial change in the 6-min walk test distance (6MWD) was also performed.
Results: Thirty-five patients on sildenafil qualified for the analysis, of which 85.7 % (30/35) were successfully transitioned. The remaining 14.3 % (5/30) (failure group) were switched back to sildenafil due to worsening symptoms. The mean pretransition 6MWD was 363 m, with an average change in the success group of +16.4 m (range = -64 to +140 m) compared to -45 m (range = -123 to +32 m) in the failure group at 1-3 months post switch (p = 0.02). All 30 patients in the success group remained on tadalafil, with an average improvement in the 6MWD of +37.04 m (range = -36.5 to +236.5 m) at 12 months post switch. The failure group had a higher daily sildenafil dose (180 vs. 115.5 mg; p = 0.06), with 42.8 % of patients at the highest sildenafil dose failing the transition.
Conclusion: The transition from sildenafil to tadalafil is safe and generally well tolerated. Patients with more severe disease and those on higher doses of sildenafil are more likely to fail the transition and should be monitored closely post switch.