A Retrospective Review of Infants Receiving Sildenafil

An Accidental Repetitive 10-Fold Overdose of Sildenafil in a Young Infant with Pulmonary Hypertension

Sildenafil is a selective phosphodiesterase type-5 inhibitor that is increasingly used to treat pulmonary hypertension (PH) in neonates. Only little is known about the relation between the dose of sildenafil, plasma concentrations, and the degree of toxicity. Here, we present a young infant with congenital diaphragmatic hernia and PH who received an unintentional 10-fold overdose of oral sildenafil for 6 consecutive days. This overdose, compared to the therapeutic dose, resulted in increased plasma concentrations of sildenafil from 42 to 521 mcg/L and desmethylsildenafil from 81 to 393 mcg/L. However, the high exposure only led to diarrhea, without any other serious adverse events. This case describes the mild symptoms upon an overdose with the role of therapeutic drug monitoring to monitor exposure in relation to symptoms and therewith support clinical decision-making.

Levels of angiotensin peptides in healthy and cardiovascular/renal-diseased paediatric population-an investigative review

The renin-angiotensin-aldosterone system (RAAS) plays a major role in the regulation of blood pressure and homeostasis. Therefore, it is a commonly used target for pharmacotherapy of cardiovascular diseases in adults. However, the efficacy of this pharmacotherapy can only be limitedly derived into children. Comprehensive knowledge of the humoral parameters acting in the paediatric RAAS (e.g. angiotensin I, angiotensin II, angiotensin 1-7, angiotensin III, and angiotensin IV) might facilitate a more effective and rational pharmacotherapy in children. Therefore, this review aims to provide an overview of the maturing RAAS. Out of 925 identified records, 35 publications were classified as relevant. Physiological and pathophysiological concentrations of angiotensin peptides were compiled and categorised according to European Medicines Agency age groups. Age has a major impact on circulating angiotensin I, angiotensin II, and angiotensin 1-7, which is reflected in an age-dependent decrease during childhood. In contrast to data obtained in adults, no gender-related differences in angiotensin levels were identified. The observed increase in peptide concentrations regarding cardiac- and renal-diseased children is influenced by surgical repair, while evidence for a pharmacological impact is conflicting. A comprehensive set of angiotensin I, angiotensin II, and angiotensin 1-7 values from neonates up to adolescents was compiled. Indicating age as a strong effector. However, evidence about potential promising targets of the RAAS like angiotensin III and angiotensin IV is still lacking in children.

Sildenafil as a Rescue Agent Following Intestinal Ischemia and Reperfusion Injury

BACKGROUND

Acute mesenteric ischemia carries a significant morbidity. Measures to improve blood flow parameters to the intestine may ameliorate the disease. Sildenafil, a phosphodiesterase 5 inhibitor, increases cyclic guanosine monophosphate and has been shown to prevent the effects of ischemia when given before injury. However, its effects as a rescue agent have not been established. We therefore hypothesized that sildenafil, when given as a rescue agent for intestinal ischemia, would improve mesenteric perfusion, limit intestinal epithelial injury, and decrease intestinal leukocyte chemoattractants.

METHODS

Eight to 12 wk-old-male C57BL/6J mice underwent laparotomy and temporary occlusion of the superior mesenteric artery for 60 min. Following ischemia, reperfusion was permitted, and before closing the abdomen, sildenafil was injected intraperitoneally in a variety of concentrations. After 24 h, reperfusion was reassessed. Animals were euthanized and intestines evaluated for histologic injury and leukocyte chemoattractants.

RESULTS

Postischemic administration of sildenafil did not improve mesenteric perfusion following intestinal ischemia and reperfusion injury. However, sildenafil did improve histologic injury scores in dose ranges of 0.01 to 10 mg/kg. No difference was noted in histological injury with 100 mg/kg dose, and all members of the 1000 mg/kg group died within 24 h of injury. Epithelial protection was not facilitated by the leukocyte chemoattractants Regulated on Activation, Normal T Cell Expressed, and Secreted, macrophage inflammatory protein 1 alpha, monocyte chemoattractant protein, neutrophil activating protein, or granulocyte colony stimulating factor.

CONCLUSIONS

Administration of sildenafil following intestinal ischemia may limit intestinal mucosal injury but does not appear to alter mesenteric perfusion or leukocyte chemoattractant influx. TYPE: Basic science.

LEVEL OF EVIDENCE

N/A.

Treatment of pediatric pulmonary arterial hypertension: A focus on the NO-sGC-cGMP pathway

OBJECTIVE

While pulmonary arterial hypertension (PAH) is rare in infants and children, it results in substantial morbidity and mortality. In recent years, prognosis has improved, coinciding with the introduction of new PAH-targeted therapies, although much of their use in children is off-label. Evidence to guide the treatment of children with PAH is less extensive than for adults. The goal of this review is to discuss the treatment recommendations for children with PAH, as well as the evidence supporting the use of prostanoids, endothelin receptor antagonists (ERAs), and phosphodiesterase type 5 inhibitors (PDE5i) in this setting.

DATA SOURCES

Nonsystematic PubMed literature search and authors' expertise.

STUDY SELECTION

Articles were selected concentrating on the nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway in PAH. The methodology of an ongoing study evaluating the sGC stimulator riociguat in children with PAH is also described.

RESULTS

Despite recent medical advances, improved therapeutic strategies for pediatric PAH are needed. The efficacy and tolerability of riociguat in adults with PAH have been well trialed.

CONCLUSION

The pooling of data across trials, supplemented by registry data, will help to confirm the safety and tolerability of prostanoids, ERAs, and PDE5i in children. Ongoing studies will clarify the place of sGC stimulators in the treatment strategy for pediatric PAH.

Clinical efficacy of tadalafil compared to sildenafil in treatment of moderate to severe canine pulmonary hypertension: a pilot study

INTRODUCTION

Canine pulmonary hypertension (PH) is associated with high morbidity and mortality. Tadalafil, a phosphodiesterase-5 inhibitor used commonly in humans with PH, has not been evaluated in a clinical trial in dogs with naturally occurring PH. Our objectives were to compare the efficacy of tadalafil and sildenafil on PH assessed by peak tricuspid regurgitant flow velocity, estimated systolic pulmonary arterial pressure gradient, voluntary activity, quality of life, and safety profiles in dogs with moderate to severe PH.

ANIMALS

Twenty-three dogs with echocardiographic evidence of moderate to severe PH were enrolled.

METHODS

A prospective short-term, randomized, double-blinded pilot study was carried out. Dogs with PH were randomly allocated to receive sildenafil or tadalafil for 2 weeks and assessed via echocardiography, activity monitors, and owner-reported outcomes.

RESULTS

Collectively, phosphodiesterase-5 inhibition significantly decreased (improved) quality of life scores (p = 0.003) and visual analog score (p = 0.024) without significant between-treatment difference of these variables. Phosphodiesterase-5 inhibition did not significantly affect peak tricuspid regurgitant flow velocity (p = 0.056) or voluntary activity (p = 0.27). A total of 33% (7/21) of dogs experienced at least one adverse event during the study (tadalafil, n = 5; sildenafil, n = 2) with no significant difference between treatment type and incidence of adverse events (p = 0.36).

DISCUSSION

In this pilot study, phosphodiesterase-5 inhibition led to apparent improvement in quality of life scores without documenting superiority of tadalafil over sildenafil.

CONCLUSION

Tadalafil at a dose of 2 mg/kg once daily appears to be a viable alternative to sildenafil in dogs with moderate to severe PH.