Risk-benefit considerations when prescribing phosphodiesterase-5 inhibitors in children

Advances in targeted therapy for pulmonary arterial hypertension in children

Pulmonary arterial hypertension (PAH) is a rare and devastating disease of the pulmonary vasculature with a high morbidity and mortality rate in infants and children. Currently, treatment approaches are mostly based on adult guidelines and pediatrician clinical experience, focusing on specific pulmonary antihypertensive therapy and conventional supportive care. The advent of targeted drugs has led to significant advances in the treatment of PAH in children, including endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and prostacyclins, which have been studied and proven to improve hemodynamics and functional class in children PAH. A new targeted drug, riociguat, is assessing its safety and efficacy in clinical trials. However, more randomized controlled studies are needed to evaluate the combination of drugs, treatment strategies, and clinical endpoints of targeted therapy in children PAH. In this review, we summarize the research advances of PAH-targeted therapy in children over the last decade in order to provide a theoretical basis for future studies.

CONCLUSION

Pulmonary arterial hypertension (PAH) is a rare and devastating pulmonary vascular disease that is associated with a variety of diseases of any age in childhood onset.

WHAT IS KNOWN

• Therapeutic strategies for targeted drugs for PAH in children are based almost exclusively on data from adult studies and clinical experience of pediatric specialists. • Due to the complex etiology of PAH in children and the relative lack of clinical trial data, the selection of appropriate targeted drug therapy remains difficult.

WHAT IS NEW

• We redefine the definition of pulmonary arterial hypertension in children and summarize the progress of targeted therapy of pulmonary arterial hypertension in children in the past ten years. • The dosage and adverse reactions were summarized, and the mechanism of action was drawn according to the available targeted drugs. It can provide theoretical support for the development of guidelines and treatment strategies for the diagnosis and treatment of pulmonary arterial hypertension in children.

The effect of tadalafil on functional capacity and echocardiographic parameters in patients with repaired Tetralogy of Fallot

BACKGROUND

Tetralogy of Fallot (TOF) is one of the most common cyanotic congenital heart diseases (CHD) in children. Various surgical procedures including palliative shunts and TOF total correction (TFTC) were done with some complications, of which, the most common is pulmonary valve regurgitation (PR). Tadalafil is a phosphodiesterase 5 inhibitor which reduces pulmonary vascular resistance, and improves right ventricular function and vascular endothelium, and may have some beneficial effects after TFTC.

METHODS

We studied 18 patients with TOF and PR, with some impaired right ventricular function after TFTC. Tadalafil tablets at a dose of 1 mg per kg (maximum 40 mg) per day as a single dose was administered orally for 8 weeks. In all patients, before and after taking tadalafil, functional class assessment, electrocardiography (ECG) changes, some echocardiographic and endothelial function parameters [flow-mediated dilation (FMD) and intima-media thickness (IMT) of carotid artery], and exercise test were determined.

RESULTS

The patient's mean age was 10.11 ± 4.03 years, and the mean age of operation was 2.52 ± 1.12 years. The effect of tadalafil on different echocardiographic parameters and also on tricuspid valve regurgitation (TR) and PR severity and gradient was not significant. Moreover, it had no effects on QRS duration. Tadalafil had a significant effect on improving FMD and exercise test (P = 0.01). The effect of tadalafil on echocardiographic parameters, carotid artery IMT, and ECG parameters was not significant (P > 0.05). Tadalafil was tolerated well, and the most common side effects were headache and myalgia.

CONCLUSION

This study showed that tadalafil is a safe and well-tolerated drug. It might improve exercise performance, endothelial function, and functional class, and possibly could allow patients a longer period of well-being and could possibly delay the need for pulmonary valve replacement (PVR).

Physicochemical Properties of Bosentan and Selected PDE-5 Inhibitors in the Design of Drugs for Rare Diseases

The study provides the physicochemical characteristic of bosentan (BOS) in comparison to tadalafil (TA) and sildenafil citrate (SIL). Despite some reports dealing with thermal characteristic of SIL and TA, physicochemical properties of BOS have not been investigated so far. Recent clinical reports have indicated that the combination of bosentan and PDE-5 inhibitor can improve the effectiveness of pharmacotherapy of pulmonary arterial hypertension (PAH). However, in order to design personalized medicines for therapy of chronic rare diseases, detailed information on the thermal behaviour and solubility of each drug is indispensable. Thus, XRD, DSC and TGA-QMS analyses were applied to compare the properties of the drugs, their thermal stability as well as to identify the products of thermal degradation. The dehydration of BOS started at 70°C and was followed by the chemical degradation with the onset at 290°C. The highest thermal stability was stated for TA, which decomposed at ca. 320°C, whereas the lowest onset of the thermal decomposition process was stated for SIL, i.e. 190°C. The products of the drug decomposition were identified. FT-FIR was applied to study intra- and intermolecular interactions between the drug molecules. FT-MIR and Raman spectroscopy were used to examine the chemical structure of the drugs. Chemoinformatic tools were used to predict the polar surface area, pKa, or logP of the drugs. Their results were in line with solubility and dissolution studies.