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Patient Tolerability and Satisfaction after Conversion from Sildenafil to Tadalafil (SITAR Study)

Louise Durst

Charles Burger

Ronald Oudiz

Veronica Franco

Robert Frantz


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Conference: 2011 PH Professional Network Symposium

Release Date: 09.22.2011

Presentation Type: Abstracts

L Durst, RN1; CD Burger, MD2; RJ Oudiz, MD3; V Franco, MD4 and RP Frantz, MD1
1. College of Medicine, Mayo Clinic, Rochester, MN 
2. Division of Pulmonary Medicine, Mayo Clinic, Jacksonville, FL 
3. LA Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 
4. Ohio State University Medical Center, Columbus, OH

OBJECTIVE: To prospectively assess the safety, tolerability and patient satisfaction with conversion from sildenafil to tadalafil.

BACKGROUND: The nitric oxide (NO) pathway is one of 3 key pathways deregulated in pulmonary arterial hypertension (PAH). Phosphodiesterase type 5 inhibitors (PDE-5Is) prevent inactivation of cGMP, a key mediator of the NO pathway, resulting in enhanced pulmonary vasodilation Sildenafil, the first PDE-5I for the treatment of PAH, was approved by the FDA at a dose of 20 mg three times daily.1,2 However, per physicians' recommendation, patients sometimes receive doses up to 100 mg three times daily in the hope that it might be more efficacious. Tadalafil is a once-daily PDE-5I approved for the treatment of patients with PAH at a dose of 40 mg daily, the highest dose studied.3,4 Clinical improvements have been observed with sildenafil and tadalafil therapy, but there is little reported clinical experience in converting patients from sildenafil to tadalafil. From a nursing perspective, we were interested in tolerance and satisfaction of switching, as well as potential impact on adherence for optimal PAH disease management.

METHODS: This was a multicenter, observational, prospective study of PAH patients clinically converted from sildenafil to tadalafil. Clinical data as available including 6 minute walk distance, WHO functional class, echocardiographic findings, hemodynamics and BNP or NBNP levels were collected from the patient record. Questionnaires including Treatment Satisfaction Questionnaire for Medication (TSQM) and PAH symptom assessments were collected at baseline, 1, 3 and 6 months post conversion.

OUTCOME: Thirty two patients transitioned from sildenafil to tadalafil. Clinician reasons cited for transition were convenience (34%), cost (34%), sildenafil dose > 20 mg three times daily (16%), or other (41%). Patients were generally advised to discontinue sildenafil following their evening dose, and start tadalafil (usually 40 mg daily) the next morning. Twenty five patients had satisfaction survey data available at 1 month follow-up. Ten patients (40%) reported greater satisfaction with tadalafil than sildenafil, ten (40%) reported about the same, and 5 (20%) reported less satisfaction. One patient switched back to sildenafil 2.5 months after conversion due to GI reflux, photosensitivity and muscle aching. The switch to tadalafil was generally well-tolerated, with a slightly higher incidence of headache, and lower incidence of diarrhea and flushing within 30 days of transition. Among patients who completed the PAH symptom questionnaire, there appeared to be a greater percentage of patients who reported the same or improved general PAH symptoms over time. Long term data will be reported at time of presentation.

IMPLICATIONS: These results demonstrate that patients transitioning from sildenafil to tadalafil generally experienced increased satisfaction and the same or improved PAH symptoms with a once-daily therapy regimen compared with a three times a day regimen, without compromising efficacy. By reducing the daily pill burden, drug-related cost as well as patient adherence to therapy may be improved.


  1. Revatio [package insert]. New York, NY: Pfizer Corporation, 2010. 
  2. Galie N, Ghofrani HA, Torbicki A, et al. N Engl J Med. 2005; 353(20): 2148-2157. 
  3. Adcirca [package insert]. Research Triangle Park, NC: United Therapeutics Corporation; 2011. 
  4. Galie N, Brundage BH, Ghofrani HA, et al, on behalf of the Pulmonary Arterial Hypertension and Response to Tadalafil (PHIRST) Study Group. Circulation. 2009; 119(22): 2894-2903.