Clinical application of tadalafil in dogs with pulmonary hypertension: a retrospective study

Pulmonary hypertension (PH) is characterized by abnormally increased pressure within the pulmonary vasculature. Phosphodiesterase type 5 (PDE5) inhibitors are commonly used to manage PH, and tadalafil, a PDE5 inhibitor with a longer half-life than sildenafil, has rarely been investigated in veterinary medicine. This retrospective study analyzed medical records of dogs treated with tadalafil at the Veterinary Medical Teaching Hospital of Jeju National University between January 2021 and July 2023. Eleven dogs tentatively diagnosed with PH received tadalafil at an initial dosage of 1 mg/kg once daily and were monitored for over 4 weeks. Efficacy and adverse effects were evaluated based on history and physical examination findings. Ten dogs had previously received sildenafil, while one dog was treated with tadalafil as first‐line therapy. Nausea occurred in one case. Seven of 11 dogs achieved at least partial remission, whereas 4 showed no improvement. Notably, 8 dogs (72.7%) were receiving concomitant medications targeting the underlying diseases causing PH, which may have contributed to symptom improvement and influenced clinical outcomes. Thus, although tadalafil at 1 mg/kg once daily was generally well tolerated and appeared to provide acceptable control of PH, its efficacy should be interpreted cautiously given the small sample size. It may be particularly beneficial when the underlying diseases causing PH are adequately managed with concomitant therapies, within the context of multimodal treatment.