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1: Respir Res. 2005 Jul 20;6(1):76.

Lung vasodilatory response to inhaled iloprost in experimental pulmonary hypertension: amplification by different type phosphodiesterase inhibitors.

Schermuly RT, Inholte C, Ghofrani HA, Gall H, Weissmann N, Weidenbach A, Seeger W, Grimminger F.
Medical Clinic II/V, Justus-Liebig-University Giessen, 35392 Giessen, Germany. ralph.schermuly@innere.med.uni-giessen.de

Inhaled prostanoids and phosphodiesterase (PDE) inhibitors have been suggested for treatment of severe pulmonary hypertension. In catheterized rabbits with acute pulmonary hypertension induced by continuous infusion of the stable thromboxane analogue U46619, we asked whether sildenafil (PDE1/5/6 inhibitor), motapizone (PDE3 inhibitor) or 8-Methoxymethyl-IBMX (PDE1 inhibitor) synergize with inhaled iloprost. Inhalation of iloprost caused a transient pulmonary artery pressure decline, levelling off within <20 min, without significant changes in blood gases or systemic hemodynamics. Infusion of 8-Methoxymethyl-IBMX, motapizone and sildenafil caused each a dose-dependent decrease in pulmonary artery pressure, with sildenafil possessing the highest efficacy and at the same time selectivity for the pulmonary circulation. When combining a per se ineffective dose of each PDE inhibitor (200 microg/kg x min 8-Methoxymethyl-IBMX, 1 microg/kg x min sildenafil, 5 microg/kg x min motapizone) with subsequent iloprost nebulization, marked amplification of the prostanoid induced pulmonary vasodilatory response was noted and the area under the curve of PPA reduction was nearly threefold increased with all approaches, as compared to sole iloprost administration. Further amplification was achieved with the combination of inhaled iloprost with sildenafil plus motapizone, but not with sildenafil plus 8MM-IBMX. Systemic hemodynamics and gas exchange were not altered for all combinations. We conclude that co-administration of minute systemic doses of selective PDE inhibitors with inhaled iloprost markedly enhances and prolongs the pulmonary vasodilatory response to inhaled iloprost, with maintenance of pulmonary selectivity and ventilation perfusion matching. The prominent effect of sildenafil may be operative via both PDE1 and PDE5, and is further enhanced by co-application of a PDE3 inhibitor.

2: Herz. 2005 Jun;30(4):296-302.

Emerging Therapies for the Treatment of Pulmonary Arterial Hypertension. [Article in German]

Ghofrani HA, Voswinckel R, Reichenberger F, Grimminger F, Seeger W.
Medizinische Klinik II, Klinikstrasse 36, 35392, Giessen, ardeschir.ghofrani@innere.med.uni-giessen.de.

Besides all progress in the therapy of pulmonary arterial hypertension over the past years, there is still no cure for this devastating disease. By introducing effective and nonparenteral medications (e. g., oral endothelin receptor antagonists [ERAs], inhaled prostanoids), quality of life, exercise tolerance and prognosis of patients have substantially improved. However, applicability of these therapies can be hampered by serious side effects and/or the necessity for elaborate application techniques. Whether selective ERAs-due to their specificity for the A-type receptor-have potential benefits over the nonselective ERA bosentan remains to be answered by the analysis of pivotal trials recently carried out with ambrisentan and sitaxsentan. Inhaled treprostinil can potentially have benefits over the already approved inhaled iloprost, related to its higher pulmonary selectivity as well as to the longer biological half-life. However, this has yet to be proven in long-term randomized controlled trials. In comparison to the previously mentioned substances, the selective phosphodiesterase-5 (PDE5) inhibitor sildenafil approached approval closest as new therapy for pulmonary arterial hypertension. Oral sildenafil has proven its efficacy as a selective pulmonary vasodilator in various forms of pulmonary hypertension. The results of the pivotal phase III trial have confirmed the strong efficacy and excellent tolerability of this substance. Combination therapies, despite all progress seen for single agents, can be regarded as the most promising therapeutic approach for the future. However, controlled randomized trials that are currently under consideration have to confirm this notion.

3: Internist (Berl). 2005 Mar;46(3):341-9.

Therapy of pulmonary arterial hypertension

Olschewski H, Ghofrani A, Enke B, Reichenberger F, Voswinckel R, Kreckel A, Ghofrani S, Wiedemann R, Schulz R, Grimminger F, Seeger W.
Medizinische Klinik, Klinikum der Justus-Liebig-Universitat Giessen.

New drugs for pulmonary arterial hypertension have shown efficacy in randomized controlled trials. Endothelin receptor antagonists (ERA) and prostanoids are most important for clinical practice. Bosentan represents the first approved orally active therapy for PAH. Besides its hepatotoxicity it is mostly well tolerated. The first approved prostanoid, epoprostenol, is currently first choice only for decompensated right heart failure in PAH. It has to be delivered continuously intravenously and is prone to complications, side effects and very high costs. Alternatively, subcutaneous treprostinil can be applied. It is less risky and expensive but may cause local pain at the infusion site. Inhaled iloprost combines the features of a prostanoid with pulmonary and intrapulmonary selectivity. Alternatively, iloprost is being used as continuous intravenous infusion. The phosphodiesterase-5 inhibitor sildenafil was effective in two randomized controlled trials but has not been approved for PAH therapy.

4: J Am Coll Cardiol. 2004 Oct 6;44(7):1488-96.

Differences in hemodynamic and oxygenation responses to three different phosphodiesterase-5 inhibitors in patients with pulmonary arterial hypertension: a randomized prospective study

Ghofrani HA, Voswinckel R, Reichenberger F, Olschewski H, Haredza P, Karadas B, Schermuly RT, Weissmann N, Seeger W, Grimminger F.
Department of Internal Medicine, University Hospital Giessen, Giessen, Germany.

OBJECTIVES: We sought to compare the short-term impact of three different phosphodiesterase-5 (PDE5) inhibitors on pulmonary and systemic hemodynamics and gas exchange parameters in patients with pulmonary arterial hypertension (PAH). BACKGROUND: The PDE5 inhibitor sildenafil has been reported to cause pulmonary vasodilation in patients with PAH. Vardenafil and tadalafil are new PDE5 inhibitors, recently being approved for the treatment of erectile dysfunction. METHODS: Sixty consecutive PAH patients (New York Heart Association functional class II to IV) who underwent right heart catheterization received short-term nitric oxide (NO) inhalation and were subsequently assigned to oral intake of 50 mg sildenafil (n = 19), 10 mg (n = 7) or 20 mg (n = 9) vardenafil, or 20 mg (n = 9), 40 mg (n = 8), or 60 mg (n = 8) tadalafil. Hemodynamics and changes in oxygenation were assessed over a subsequent 120-min observation period. RESULTS: All three PDE5 inhibitors caused significant pulmonary vasorelaxation, with maximum effects being obtained after 40 to 45 min (vardenafil), 60 min (sildenafil), and 75 to 90 min (tadalafil). Sildenafil and tadalafil, but not vardenafil, caused a significant reduction in the pulmonary to systemic vascular resistance ratio. Significant improvement in arterial oxygenation (equally to NO inhalation) was only noted with sildenafil. CONCLUSIONS: In PAH patients, the three PDE5 inhibitors differ markedly in their kinetics of pulmonary vasorelaxation (most rapid effect by vardenafil), their selectivity for the pulmonary circulation (sildenafil and tadalafil, but not vardenafil), and their impact on arterial oxygenation (improvement with sildenafil only).

Careful evaluation of each new PDE5 inhibitor, when being considered for PAH treatment, has to be undertaken, despite common classification as PDE5 inhibitors.

Publication Types: Clinical Trial Randomized Controlled Trial

5: Ann Intern Med. 2004 Aug 3;141(3):169-77.
Comment in: Ann Intern Med. 2004 Aug 3;141(3):233-5. Ann Intern Med. 2004 Aug 3;141(3):I12.

Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest base camp: a randomized, double-blind, placebo-controlled crossover trial.

Ghofrani HA, Reichenberger F, Kohstall MG, Mrosek EH, Seeger T, Olschewski H, Seeger W, Grimminger F.
University Hospital Giessen and Justus-Liebig University, Giessen, Germany.

BACKGROUND: Alveolar hypoxia causes pulmonary hypertension and enhanced right ventricular afterload, which may impair exercise tolerance. The phosphodiesterase-5 inhibitor sildenafil has been reported to cause pulmonary vasodilatation. OBJECTIVE: To investigate the effects of sildenafil on exercise capacity under conditions of hypoxic pulmonary hypertension. DESIGN: Randomized, double-blind, placebo-controlled crossover study. SETTING: University Hospital Giessen, Giessen, Germany, and the base camp on Mount Everest. PARTICIPANTS: 14 healthy mountaineers and trekkers.

MEASUREMENTS: Systolic pulmonary artery pressure, cardiac output, and peripheral arterial oxygen saturation at rest and during assessment of maximum exercise capacity on cycle ergometry 1) while breathing a hypoxic gas mixture with 10% fraction of inspired oxygen at low altitude (Giessen) and 2) at high altitude (the Mount Everest base camp). INTERVENTION: Oral sildenafil, 50 mg, or placebo. RESULTS: At low altitude, acute hypoxia reduced arterial oxygen saturation to 72.0% (95% CI, 66.5% to 77.5%) at rest and 60.8% (CI, 56.0% to 64.5%) at maximum exercise capacity. Systolic pulmonary artery pressure increased from 30.5 mm Hg (CI, 26.0 to 35.0 mm Hg) at rest to 42.9 mm Hg (CI, 35.6 to 53.5 mm Hg) during exercise in participants taking placebo. Sildenafil, 50 mg, significantly increased arterial oxygen saturation during exercise (P = 0.005) and reduced systolic pulmonary artery pressure at rest (P < 0.001) and during exercise (P = 0.031). Of note, sildenafil increased maximum workload (172.5 W [CI, 147.5 to 200.0 W]) vs. 130.6 W [CI, 108.8 to 150.0 W]); P < 0.001) and maximum cardiac output (P < 0.001) compared with placebo. At high altitude, sildenafil had no effect on arterial oxygen saturation at rest and during exercise compared with placebo. However, sildenafil reduced systolic pulmonary artery pressure at rest (P = 0.003) and during exercise (P =0.021) and increased maximum workload (P = 0.002) and cardiac output (P = 0.015). At high altitude, sildenafil exacerbated existing headache in 2 participants. LIMITATIONS: The study did not examine the effects of sildenafil on normoxic exercise tolerance. CONCLUSIONS: Sildenafil reduces hypoxic pulmonary hypertension at rest and during exercise while maintaining gas exchange and systemic blood pressure. To the authors' knowledge, sildenafil is the first drug shown to increase exercise capacity during severe hypoxia both at sea level and at high altitude.

Publication Types: Clinical Trial Randomized Controlled Trial

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