Tadalafil Dosing for Pulmonary Arterial Hypertension
Yes, tadalafil is taken at 40 mg once daily for pulmonary arterial hypertension (PAH), not 20 mg. 1
Correct Dosing Information
- The recommended dose of tadalafil for PAH is 40 mg once daily 1
- Treatment with more than the recommended dose of tadalafil (40 mg once daily) has not been studied and is not recommended 1
- Unlike sildenafil (which is dosed at 20 mg three times daily for PAH), tadalafil has a longer half-life allowing for once-daily dosing 2
Clinical Evidence Supporting 40 mg Dosing
- In the PHIRST trial, 406 PAH patients were treated with tadalafil at various doses (2.5,10,20, or 40 mg once daily) 1
- Only the 40 mg dose showed favorable results on all key outcomes: exercise capacity, symptoms, hemodynamics, and time to clinical worsening 1
- The mean placebo-corrected increase in 6-minute walk distance (6MWD) was 33 meters for patients receiving 40 mg tadalafil once daily 3
- In treatment-naïve patients, tadalafil 40 mg once daily significantly increased the mean placebo-corrected 6MWD by 44 meters at week 16 4
Clinical Benefits of Tadalafil 40 mg Daily
- Improves 6-minute walk distance (6MWD) 1
- Improves WHO functional class (FC) 1
- Delays time to clinical worsening 1
- Improves cardiopulmonary hemodynamics 1
- Reduces pulmonary vascular resistance 2
- Improves health-related quality of life scores 3, 5
Safety Profile
- Tadalafil is generally well tolerated with adverse events that are typically mild to moderate in intensity 3, 5
- Side effects are similar to those of sildenafil, mainly related to vasodilation (headache, flushing, epistaxis) 1
- Discontinuation rates due to adverse events are usually low 5
- The combination of tadalafil with riociguat is contraindicated due to risk of systemic hypotension 1
Important Clinical Considerations
- Tadalafil can be used as monotherapy or in combination with other PAH medications, particularly endothelin receptor antagonists like bosentan or macitentan 6, 4
- When used as add-on therapy to bosentan, the placebo-adjusted improvement in 6MWD was 23 meters, which was less than the 44 meters seen in treatment-naïve patients 4
- A new fixed-dose combination of macitentan and tadalafil in a single tablet has shown significant improvement in pulmonary vascular resistance compared to either monotherapy 6
Common Pitfalls
- Confusing the dosing with sildenafil (another PDE-5 inhibitor for PAH), which is dosed at 20 mg three times daily 1
- Confusing the PAH dosing with erectile dysfunction dosing, which typically uses lower doses 2
- Attempting to increase the dose beyond 40 mg daily, which has not been studied and is not recommended 1
- Combining tadalafil with riociguat, which is contraindicated due to risk of hypotension 1