Sildenafil in Infants and Children

Exploring the Multifaceted Potential of Sildenafil in Medicine

Phosphodiesterase type 5 (PDE5) is pivotal in cellular signalling, regulating cyclic guanosine monophosphate (cGMP) levels crucial for smooth muscle relaxation and vasodilation. By targeting cGMP for degradation, PDE5 inhibits sustained vasodilation. PDE5 operates in diverse anatomical regions, with its upregulation linked to various pathologies, including cancer and neurodegenerative diseases. Sildenafil, a selective PDE5 inhibitor, is prescribed for erectile dysfunction and pulmonary arterial hypertension. However, considering the extensive roles of PDE5, sildenafil might be useful in other pathologies. This review aims to comprehensively explore sildenafil's therapeutic potential across medicine, addressing a gap in the current literature. Recognising sildenafil's broader potential may unveil new treatment avenues, optimising existing approaches and broadening its clinical application.

Sildenafil for congenital heart diseases induced pulmonary hypertension, a meta-analysis of randomized controlled trials

BACKGROUND

Sildenafil was first prescribed for angina pectoris and then for erectile dysfunction from its effects on vascular smooth muscle relaxation and vasodilatation. Recently, sildenafil has been proposed for congenital heart diseases induced pulmonary hypertension, which constitutes a huge burden on children's health and can attribute to fatal complications due to presence of unoxygenated blood in the systemic circulation. Therefore, our meta-analysis aims to further investigate the safety and efficacy of sildenafil on children population.

METHODS

We searched the following electronic databases: PubMed, Cochrane CENTRAL, WOS, Embase, and Scopus from inception to April 20th, 2022. Randomized controlled trials that assess the efficacy of using sildenafil in comparison to a placebo or any other vasodilator drug were eligible for inclusion. The inverse variance method was used to pool study effect estimates using the random effect model. Effect sizes are provided in the form of mean difference (MD) with 95% confidence intervals (CI).

RESULTS

Our study included 14 studies with (n = 849 children) with a mean age of 7.9 months old. Sildenafil showed a statistically significant decrease over placebo in mean and systolic pulmonary artery pressure (PAP) with MD -7.42 (95%CI [-13.13, -1.71], P = 0.01) and -8.02 (95%CI [-11.16, -4.88], P < 0.0001), respectively. Sildenafil revealed a decrease in mean aortic pressure and pulmonary artery/aortic pressure ratio over placebo with MD -0.34 (95%CI [-2.42, 1.73], P = 0.75) and MD -0.10 (95%CI [-0.11, -0.09], P < 0.00001), respectively. Regarding post corrective operations parameters, sildenafil had a statistically significant lower mechanical ventilation time, intensive care unit stay, and hospital stay over placebo with MD -19.43 (95%CI [-31.04, -7.81], s = 0.001), MD -34.85 (95%CI [-50.84, -18.87], P < 0.00001), and MD -41.87 (95%CI [-79.41, -4.33], P = 0.03), respectively. Nevertheless, no difference in mortality rates between sildenafil and placebo with OR 0.25 (95%CI 0.05, 1.30], P = 0.10) or tadalafil with OR 1 (95%CI 0.06, 17.12], P = 1).

CONCLUSION

Sildenafil is a well-tolerated treatment in congenital heart diseases induced pulmonary hypertension, as it has proven its efficacy not only in lowering both PAP mean and systolic but also in reducing the ventilation time, intensive care unit and hospital stay with no difference observed regarding mortality rates.

The effect of cardioplegic supplementation with sildenafil on cardiac energetics in a piglet model of cardiopulmonary bypass and cardioplegic arrest with warm or cold cardioplegia

Cardioplegic cardioprotection strategies used during paediatric open-heart surgery remain suboptimal. Sildenafil, a phosphodiesterase 5 (PDE-5) inhibitor, has been shown to be cardioprotective against ischemia/reperfusion injury in a variety of experimental models and this study therefore tested the efficacy of supplementation of cardioplegia with sildenafil in a piglet model of cardiopulmonary bypass and arrest, using both cold and warm cardioplegia protocols. Piglets were anaesthetized and placed on coronary pulmonary bypass (CPB), the aorta cross-clamped and the hearts arrested for 60 min with cardioplegia with or without sildenafil (10 nM). Twenty minutes after removal of cross clamp (reperfusion), attempts were made to wean the pigs from CPB. Termination was carried out after 60 min reperfusion. Throughout the protocol blood and left ventricular tissue samples were taken for analysis of selected metabolites (using HPLC) and troponin I. In both the cold and warm cardioplegia protocols there was evidence that sildenafil supplementation resulted in faster recovery of ATP levels, improved energy charge (a measure of metabolic flux) and altered release of hypoxanthine and inosine, two purine catabolites. There was no effect on troponin release within the studied short timeframe. In conclusion, sildenafil supplementation of cardioplegia resulted in improved cardiac energetics in a translational animal model of paediatric CPB surgery.

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.

Efficacy of sildenafil and high-dose anakinra in an MIS-C patient with pulmonary vasculitis: A case report

Multisystem inflammatory syndrome in children (MIS-C) is a newly identified clinical entity still not very well known in terms of epidemiology, pathogenesis, and long-term outcome. Pulmonary involvement with acute respiratory failure is an unusual life-threatening complication of MIS-C, often a reason for admission to the pediatric intensive care unit (PICU) and the use of mechanical ventilation. We present a case of a 7-year-old male patient, previously healthy, hospitalized for MIS-C, treated with intravenous immunoglobulins (IVIG), high dose methylprednisolone, and anakinra. After 2 days of the aforementioned therapy, the patient presented with hypoxia (SatO₂: 85% in ambient air room) and breathing difficulties. A chest computed tomography (CT) scan showed the presence of multiple bilateral basal parenchymal thickening and small basal pleural effusion and an arterial blood gas analysis revealed severe hypoxia (PaO₂/FiO₂ ratio, 170 mmHg). Because of a worsening of respiratory distress, the patient was transferred to the PICU, where invasive mechanical ventilation and a continuous infusion of anakinra (12 mg/kg/day) were started. An echocardiogram was performed, which showed an increase in pulmonary pressure (40 mmHg) with normal heart ejection fraction (55%), and the hypothesis of pulmonary vasculitis involving the pulmonary arterioles was made. Therefore, therapy with sildenafil (0.15 mg/kg/day) was promptly set up, with an immediate improvement of the clinical picture of respiratory failure, reduction of pulmonary pressure (23 mmHg), and subsequent extubation at 36 h with a regular clinical course until discharge. As far as we know, our case represents the first report of pulmonary vasculitis in an MIS-C patient. The use of sildenafil and high-dose continuous anakinra may represent a rescue therapy in cases of MIS-C with pulmonary vasculitis or with difficulty in extubation, allowing a short-term hospitalization in intensive care and improving the long-term outcome in these patients.

Treatment of pulmonary arterial hypertension in children

Pulmonary arterial hypertension (PAH) is a devastating illness causing already significant morbidity in childhood. Currently approved treatment options for children comprise the endothelin receptor antagonist bosentan, as well as the phosphodiesterase-5 inhibitor sildenafil. But PAH treatment has advanced significantly over the past decade, and new classes of targeted drug therapies, such as stimulators of the soluble guanylate cyclase (riociguat) or prostacyclin receptor agonists (selexipag), are currently evaluated regarding their efficacy and safety in children, in order to limit off-label use. Due to the different etiologies in children, such as PAH-CHD, there is no evidence that initial combination therapy in children is superior to a mono-therapy with respect to survival. Special attention should also be paid to the pharmacology of PAH drugs in children, which might be impacted by ontogeny or drug-drug-interactions. Therapeutic drug monitoring may be useful in pediatric patients. There is a clear need for more controlled studies of PAH medications, alone or in combination therapy in the pediatric age group. Data from clinical trials as well as from patient registries should be pooled to optimize drug development and evaluation, trial design, and evidence-based pharmacotherapy in pediatric patients with PAH. In this review, the current treatment options of pediatric PAH are summarized, and an overview of new treatment concepts, which are already evaluated in adults, is presented.

Update on the use of sildenafil in neonatal pulmonary hypertension: a narrative review of the history, current administration, and future directions

Pulmonary hypertension (PH) is a life-threatening syndrome in neonates and has multiple and varied etiologies. However, few clinical studies have systematically evaluated the treatment regimens for this population. Phosphodiesterase (PDE) inhibitors, such as milrinone, tadalafil, dipyridamole, and sildenafil, are the most important regulators of vascular relaxation in the normal pulmonary vascular transition after birth, and these agents are widely used in the treatment of PH. Sildenafil, a representative PDE-5 inhibitor, has an important role as a single mode of therapy. However, the lack of evidence from pharmacokinetic and clinical trials has limited the emergence of standardized treatment regimens for sildenafil. There are also differing opinions among researchers regarding the best route of sildenafil administration. Due to the interindividual variability in the neonatal population, it is worth selecting the most suitable route of sildenafil administration according to the specific conditions of the neonatal population. These may be evaluated using the oxygenation index (OI), pulmonary artery pressure, mean blood pressure, and the serological index. This article reviews the clinical data on the use of sildenafil, focusing on the current and promising alternative routes of administration, which may affect subsequent clinical research in term and preterm neonates.

Prophylactic Sildenafil in Preterm Infants at Risk of Bronchopulmonary Dysplasia: A Pilot Randomized, Double-Blinded, Placebo-Controlled Trial

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the need for oxygen therapy at 36 weeks postmenstrual age (PMA). Sildenafil has been shown to enhance the lung alveolarization and vascularization in newborn animal models after lung injury and has possible therapeutic potential for the prevention of BPD.

OBJECTIVE

To perform a proof-of-concept, Phase II, pilot randomized, double-blind, clinical trial to study the efficacy of sildenafil in preventing BPD, in postnatal (< 24 h), extremely and very preterm infants.

METHODS

This Phase II, pilot randomized, double-blind, clinical trial was conducted in the Neonatal Intensive Care Unit of Women's Wellness and Research Center, Doha, Qatar during 2012-2014. Infants of 24^0/7-29^6/7 weeks' gestation were eligible if they needed respiratory or oxygen support ≥ 25% at randomization, and if they were at a postnatal age of < 24 h at randomization. Forty preterm infants were randomly assigned to receive off-label oral sildenafil (0.5 mg/kg every 6 h) or a placebo solution, for one week. The primary endpoints were the incidence of BPD and death at 36 weeks PMA, and the side effects. Secondary outcomes included the incidence of BPD and the respiratory support at day 28 of life, duration of oxygen use, fraction of inspired oxygen use at 36 weeks and 28 days of life, duration of hospitalization, and the incidence of significant retinopathy of prematurity, severe intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis, patent ductus arteriosus, and late sepsis.

RESULTS

No significant differences were observed between the sildenafil and placebo study groups in mortality at 36 weeks PMA (10% vs 20%, p = 1), respiratory support at 36 weeks (30% vs 25%, p = 0.57), and side effects (0% vs 0%). For all other secondary outcomes, no significant differences were detected.

CONCLUSIONS

While not associated with side effects, off-label oral sildenafil did not demonstrate benefits in the prevention of BPD or death in the extreme and very preterm infants. Future studies of dosing and efficacy that target different regimens of sildenafil are warranted before sildenafil is recommended for the prevention of BPD.

Efficacy and safety of oral sildenafil in cystic fibrosis children with mild to moderate lung disease

BACKGROUND

Airway inflammation due to chronic infection is the leading cause of respiratory failure and death in most of patients with cystic fibrosis (CF). There is some evidence about anti-inflammatory activity of phosphodiesterase inhibitors in adult patients with CF. This study was designed to evaluate the efficacy, safety, and tolerability of sildenafil (a phosphodiesterase inhibitor drug) in children with CF.

METHOD

This uncontrolled before-after study was conducted on 20 children with CF (mean age 14 ± 2.8 years, 50% male) with mild to moderate lung disease who were referred to CF clinic of Imam Hossein hospital in Isfahan, Iran. The patients received oral sildenafil (1 mg/kg p.o tid for 3 months). Changes in spirometric values, maximal exercise capacity, and patient-reported health by using the cystic fibrosis questionnaire-revised (CFQ-R) were evaluated before and after treatment.

RESULT

CFQ-R (69.54 ± 4.6 vs 76.90 ± 5.4; P < .001) and exercise duration (401 ± 45.6 vs 497 ± 60.1 second; P < .01) increased following sildenafil therapy. In contrast, the forced expiratory value (FEV_1; 84.60 ± 13.67 vs 78.40 ± 12.95; P < .001) and FEF25-75 (77.80 ± 27.33 vs 69.20 ± 21.91; P = .004) showed significant decreases. However, the mean of FEV₁ /forced vital capacity did not change significantly during the study (P = .682).

CONCLUSIONS

Although sildenafil can improve the quality of life and exercise capacities in CF children, it significantly decreases lung function. So, administration of this drug for CF children should be reconsidered.

Chronical treatment with sildenafil causes Achilles tendinopathy in rats

AIMS

The primary goal was to assess the effects of chronic sildenafil treatment over the Achilles tendons in rats.

MAIN METHODS

Animals were divided into two groups, control and sildenafil administration (n = 5). After 60 days, the tendons were subject to biochemical and image analysis to compare tendons between the groups: collagen I and decorin content, polarisation microscopy and birefringence analysis, and tissue zymography.

KEY FINDINGS

The animals exposed to sildenafil presented a much less organised tendon matrix, with reduced collagen I and non-collagenous protein content and a much higher decorin content.

SIGNIFICANCE

The results observed in the animals can be characterised as tendinopathy, a condition not yet described as a sildenafil side effect.

Sildenafil Citrate Liposomes for Pulmonary Delivery by Ultrasonic Nebulization

Technological advances in lipid vesicles facilitate optimization of their properties to achieve therapeutic goals and promote alternative drug administration routes. Sildenafil citrate (SC) is orally administered for the treatment of pulmonary hypertension, but local release would be advantageous in terms of efficacy and safety. In the present study, liposomes from egg phosphatidylcholine and cholesterol loaded with SC, with and without d-α-tocopheryl polyethylene glycol 1000 succinate (Vit E TPGS), were prepared by sonication of the components. A transmembrane pH gradient was applied for active loading of liposomes, and the size, zeta potential, and entrapment efficiency (EE%) were determined. The liposomes were lyophilized and then nebulized. The nebulized samples were collected and the EE% was determined. The transmembrane pH gradient produced a significant increase in the EE% (from 17.68 ± 4.25% to 89.77 ± 7.64%) and, after lyophilization, the EE% remained the same as that of the originals, but the size and zeta potential were modified. EE% of liposomes decreased upon nebulization, particularly for those with Vit E TPGS. Thus, the additives used for lyoprotection reduced the impact of nebulization. Additional studies are essential, but according to these results, SC-loaded liposomes can be considered as suitable and safe carriers for the local release of sildenafil in the pulmonary system.