Benefits of Long-Term Combination Therapy with Sildenafil Citrate and Beraprost Sodium in a Dog with Pulmonary Hypertension

Background Pulmonary hypertension, defined as sustained elevated pulmonary artery pressure, can lead to right-sided heart failure if untreated. While sildenafil citrate is a common treatment, recent findings suggest that its combination with beraprost sodium may enhance therapeutic efficacy in human medicine. This case report describes the successful management of canine pulmonary hypertension using combination therapy and suggests potential efficacy in veterinary medicine. Case presentation A 12-year-old, spayed female, Pekingese dog was referred to a veterinary medical teaching hospital owing to frequent episodes of syncope and exercise intolerance. On thoracic auscultation, a grade 4 heart murmur was detected on both sides of the chest, along with respiratory sinus arrhythmia. An electrocardiogram showed a right axis deviation, suggesting possible right ventricular hypertrophy. There were no abnormalities in heart size on thoracic radiographs. An increased contact area was observed between the sternum and the right heart in the lateral view owing to the enlarged right-sided heart. No significant pulmonary infiltration, tracheal collapse, or bronchial collapse was observed. Echocardiography revealed moderate tricuspid regurgitation and severe pulmonary hypertension. Based on clinical signs and diagnostic findings, the diagnosis was right-sided heart failure caused by brachycephalic obstructive airway syndrome (BOAS). The initial treatment plan included sildenafil citrate at 2mg/kg PO bid, pimobendan at 0.3mg/kg PO bid, enalapril at 0.5mg/kg PO bid, and furosemide at 1mg/kg PO bid. Despite taking medications for three months, the frequency of syncope episodes remained unchanged, and the pulmonary hypertension failed to improve. Therefore, beraprost sodium, a prostacyclin analog, was added to the treatment regimen. Thereafter, the dog’s clinical signs of syncope significantly improved, although the echocardiographic findings showed no change in tricuspid regurgitation and the severity of pulmonary hypertension (velocity 4.42m/s, pressure gradient 78.2mmHg). The dog maintained these improved clinical signs for 12 months, with a combination of sildenafil citrate at 3 mg/kg PO bid and beraprost sodium at 20 µg/kg PO bid. Conclusions This study showed that combining beraprost sodium with sildenafil significantly improved clinical symptoms in cases where sildenafil alone was ineffective, with no adverse effects observed over an extended treatment period.