Pharmacokinetic and Pharmacodynamic Comparison of Sildenafil-Bosentan and Sildenafil-Ambrisentan Combination Therapies for Pulmonary Hypertension

Changes in CYP3A4 Enzyme Expression and Biochemical Markers Under Acute Hypoxia Affect the Pharmacokinetics of Sildenafil

To investigate the effects of pathological, physiological, biochemical and metabolic enzymes CYP3A4 on the pharmacokinetics of sildenafil under acute hypoxia, rats were randomly divided into the plain group (50 m above sea level), acute plateau group 1 (2300 m above sea level), and acute plateau group 2 (4300 m above sea level), and blood samples and liver tissues were collected. Our results showed that the blood gas, physiological and biochemical indexes of rats changed under acute hypoxia, and the protein expression of CYP3A4 enzyme decreased. The process of absorption, distribution, metabolism and excretion of sildenafil in rats has changed. Compared with the P group, the area under the drug-time curve and the average resident in the H2 group increased to 213.32 and 72.34%, respectively. The half-life and peak concentration increased by 44.27 and 133.67%, respectively. The clearance rate and apparent distribution volume decreased to 69.13 and 46.75%, respectively. There were no statistical differences in the pharmacokinetic parameters between the P group and the H1 group. In conclusion, the pharmacokinetic changes of sildenafil have a multi-factor regulation mechanism, and changes in blood gas, pathology, and biochemical indicators and metabolic enzymes affect the absorption, distribution, excretion, and metabolism of sildenafil, respectively. This study provides experimental evidence and new ideas for the rational use of sildenafil under acute hypoxic conditions.

Safety and efficacy of transitioning from the combination of bosentan and sildenafil to alternative therapy in patients with pulmonary arterial hypertension

The combination of bosentan and sildenafil is commonly used to treat patients with pulmonary arterial hypertension (PAH); however, there is evidence of a significant drug interaction between these two medications. We sought to evaluate the safety and efficacy of transitioning patients with PAH from the combination of bosentan and sildenafil to alternative therapy. A retrospective database review was performed on 16 patients with PAH who were treated with the combination of bosentan and sildenafil and transitioned to alternative treatment at our center. Invasive and non-invasive patient parameters were collected at baseline and after transition. 56.3% of patients were in World Health Organization functional class (WHO FC) III and a majority of patients (68.7%) were on background prostacyclin therapy. The most common reason for transition was concern for a drug interaction in seven patients (43.8%). The most common transition was bosentan to macitentan in eight patients (50%). Fifteen patients (93.8%) tolerated the transition after a median follow-up of 6.5 months with minor adverse events occurring in four patients (25%). In 11 patients, 6-min walk distance (6MWD) was unchanged comparing baseline to post transition measurements with a median change of +8 m (range: −50 to + 70; P = 0.39). Nine patients (81.8%) had stable (within 15% margin) or significant improvement (increase by ≥15%) in 6MWD after transition. All patients demonstrated stable or improved WHO FC after transition. There were no significant changes after transition in hemodynamics, N-terminal pro-brain natriuretic peptide (NT-proBNP) values, or Registry to Evaluate Early and Long-Term PAH Disease Management (REVEAL) risk scores. In our study, transitioning patients from bosentan and sildenafil to alternative therapy was safe and resulted in clinical stability.

[Advantages and limitations of initial combination therapy in pulmonary arterial hypertension patients in Russia]

Pulmonary arterial hypertension (PAH) is severe and often times rapidly progressive disease with fatal outcome. The concept of initial combination of PAH-specific therapies in high risk patients at baseline was first described in the European guidelines on pulmonary hypertension (PH) in 2009, and in low or intermediate risk patients at baseline in 2015. Interestingly, that in Cologne Experts Consensus, and then in the 6th World Symposium on PH medical community started considering initial combination therapy as one of the most important pillars in PAH treatment algorithms in 2018. As of August 2020, as many as 8 formulations of 7 reference PAH-specific drugs are licensed for medical use in the Russian Federation. On top of that, 6 abbreviated drugs (generics) have also become available few years ago. Unfortunately, intravenous and subcutaneous prostacyclin analogs (PCA) and tadalafil are not approved for PH patients treatment in the Russian Federation. In this narrative review paper we attempted to describe studies on initial dual combination therapy with PAH-specific drugs registered in Russia, i.e. ambrisentan and riociguat, macitentan and riociguat, macitentan and sildenafil in low or intermediate risk patients at baseline, as well as iloprost inhaled and sildenafil, iloprost inhaled and bosentan in high risk patients. Some beneficial pharmacological effects due to the synergy between ambrisentan plus riociguat, and inhaled iloprost plus sildenafil appear to be interesting and require further clinical confirmation. Other initial combinations of PAH-specific agents require large-scale clinical trials as well.

Effect of Combination Therapy of Endothelin Receptor Antagonist and Phosphodiesterase-5 Inhibitor on Clinical Outcome and Pulmonary Haemodynamics in Patients with Pulmonary Arterial Hypertension: A Meta-Analysis

BACKGROUND

The combination of an endothelin receptor antagonist and a phosphodiesterase-5 inhibitor having different biological targets has become an integral part of the treatment of pulmonary arterial hypertension; however, several clinical studies have reported conflicting results.

OBJECTIVE

The objective of this meta-analysis was to evaluate the effect of an endothelin receptor antagonist and phosphodiesterase-5 inhibitor combination in pulmonary arterial hypertension.

METHODS

After performing a comprehensive literature search in MEDLINE, Cochrane and the International Clinical Trial Registry Platform, reviewers assessed eligibility and extracted data from seven relevant articles (publications till December 2018). PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed in the selection, analysis and reporting of findings. The odds ratio and mean difference were calculated to estimate the difference in clinical worsening, 6-minute walking distance, pulmonary vascular resistance and N-terminal pro-brain natriuretic peptide between the groups. Quality assessment was performed using the risk of bias assessment tool and a meta-regression for probable variables affecting effect size.

RESULTS

The random-effect model analysis revealed an odds ratio of 0.56 [95% confidence interval (CI) 0.41-0.76; p = 0.0002] for clinical worsening, mean difference of 15.64 (95% CI 2.67-28.61; p = 0.02) for 6-minute walking distance, - 1.66 (95% CI - 3.82 to 0.50; p = 0.13) for pulmonary vascular resistance and - 21.04 (95% CI - 26.87 to - 15.22; p < 0.00001) for N-terminal pro-brain natriuretic peptide. The meta-regression showed no statistically significant association between the dose and duration of treatment and outcomes (odds ratio of clinical worsening and mean difference of 6-minute walking distance).

CONCLUSIONS

In pulmonary arterial hypertension, endothelin receptor antagonist and phosphodiesterase-5 inhibitor combination therapy significantly improved 6-minute walking distance, clinical worsening and N-terminal pro-brain natriuretic peptide compared with the monotherapy but did not offer any advantage in improving pulmonary vascular resistance.

PROSPERO REGISTRATION NO

CRD42018091133.

Surveillance on The Safety and Efficacy of Ambrisentan (Volibris Tablet 2.5 mg) in Patients with Pulmonary Arterial Hypertension in Real Clinical Practice: Post-marketing Surveillance (Interim Analysis Report)

BACKGROUND AND OBJECTIVE

Pulmonary arterial hypertension (PAH) is an intractable and rare disease and the accumulation of clinical evidence under real-world setting is needed. A post-marketing surveillance for the endothelin receptor antagonist ambrisentan (Volibris tablet) has been conducted by all-case investigation since September 2010. This paper is an interim report on the safety and efficacy of ambrisentan in 702 patients with PAH.

METHODS

PAH patients aged 15 years or older were subjected to the analysis. The safety analysis by overall cases or stratification of patient backgrounds and the efficacy analysis were investigated.

RESULTS

Regarding patient characteristics, the 702 patients subjected to safety analysis included 543 (77.4%) women and 546 (77.8%) patients at WHO functional class II/III. The mean observational time was 392.7 days. A total of 324 adverse drug reaction (ADR) occurred in 204 (29.1%) patients. Common ADRs (≥ 2%) included anemia (4.6%), peripheral edema (4.1%), headache (3.6%), edema and face edema (2.6% each), abnormal hepatic function (2.3%), and epistaxis (2.1%). There were 82 serious ADRs occurring in 44 (6.3%) patients (385 serious adverse events in 184 (26.2%) patients). Although 11 (1.6%) interstitial lung disease (ILD) cases were reported, all were observed in patients with disease that may contribute to ILD and therefore it is difficult to assess if ambrisentan was associated with these events. There was no difference in safety in relation to the presence/absence of connective tissue disease-related PAH (CTD-PAH) or combination therapy. Among 677 patients subjected to efficacy analysis, those in whom hemodynamic status was determined before and after treatment showed improvement in the mean pulmonary arterial pressure and pulmonary vascular resistance after treatment.

CONCLUSION

The interim results showed safety consistent with the known profile of ambrisentan in terms of the types and frequencies of ADRs in patients with PAH in real clinical practice, in comparison with previous clinical trials in Japan and the rest of the world. Thus, these results provided another corroboration of the tolerability of ambrisentan and we continue to monitor proper use information via the post-marketing surveillance to ensure any new safety signals are identified in a timely manner (ClinTrial.gov: NCT01406327).