Inhaled Sodium Nitrite Research Articles

Efficacy and safety of inhaled nebulized sodium nitrite in asthmatic patients

BackgroundNitrite is a physiologic nitric oxide (NO) derivative that can be bioactivated to NO. NO has been shown to attenuate airway inflammation and enhance the anti-inflammatory effect of corticosteroids in the animal model of asthma. Here, we aimed to investigate the efficacy and safety of inhaled sodium nitrite as add-on therapy with inhaled corticosteroid (ICS) in adult patients with persistent asthma. MethodsIn protocol 1, 10 asthmatic patients were administered a single dose of nebulized 15-mg sodium nitrite to assess safety, effect on lung function, and pharmacokinetics of nitrite within 120 min. In protocol 2, 20 patients were randomly assigned to a nitrite (15 mg twice daily) group or a placebo group to assess the efficacy over 12 weeks. The primary outcome was the forced expiratory volume in 1 s (FEV1). The secondary outcomes were other lung function parameters, unplanned asthma-related visits at the emergency department (ED) or outpatient department (OPD), admission days, asthma control test (ACT), and safety. ResultsNebulized sodium nitrite had neither acute adverse effect nor effect on lung function test within 120 min. No blood pressure change was seen. At week 12, FEV1 increased in the nitrite group, whereas there was no change in the placebo group. There were 5 events of asthma exacerbation, 4 ED visits, and one unplanned OPD visit in the placebo group, but none of these was noted in the nitrite group. There was no change in ACT scores in both groups. No adverse event was reported during 12 weeks in the nitrite group. There was no change in methemoglobin levels and sputum inflammatory markers. ConclusionFrom our pilot trial, nebulized sodium nitrite is safe in asthmatic patients, and shows the potential to reduce asthma exacerbation compared with placebo.

The Effects of Inhaled Sodium Nitrite on Pulmonary Vascular Impedance in Patients With Pulmonary Hypertension Associated with Heart Failure With Preserved Ejection Fraction

BackgroundThe severity of pulmonary hypertension (PH) is monitored by measuring pulmonary vascular resistance, which is a steady-state measurement and ignores the pulsatile load encountered by the right ventricle (RV). Pulmonary vascular impedance (PVZ) can depict both steady-state and pulsatile forces, and thus may better predict clinical outcomes. We sought to calculate PVZ in patients with PH associated with heart failure with preserved ejection fraction who were administered inhaled sodium nitrite to better understand the acute effects on afterload. Methods and ResultsFourteen patients with PH associated with heart failure with preserved ejection fraction underwent right heart catherization and were administered inhaled sodium nitrite. A Fourier transform was used to calculate PVZ for both before and after nitrite for comparison. Inhaled sodium nitrite decreased characteristic impedance (inversely related to proximal pulmonary artery compliance) and total work performed by the RV. RV efficiency improved, defined by a reduction in the total work divided by cardiac output. There was a mild decrease in pulmonary steady-state resistance after the administration of inhaled sodium nitrite, but this effect was not significant. ConclusionsPVZ analysis showed administration of inhaled sodium nitrite was associated with an improvement in pulmonary vascular compliance via a decrease in characteristic impedance, more so than pulmonary steady-state resistance. This effect was associated with improved RV efficiency and total work.

Pharmacokinetics and pharmacodynamics of single dose of inhaled nebulized sodium nitrite in healthy and hemoglobin E/β-thalassemia subjects

Inhaled sodium nitrite has been reported to decrease pulmonary artery pressure in hemoglobin E/β-thalassemia (HbE/β-thal) patients with pulmonary hypertension. This study investigated the pharmacokinetics and pharmacodynamics of inhaled nebulized sodium nitrite in 10 healthy subjects and 8 HbE/β-thal patients with high estimated pulmonary artery pressure. Nitrite pharmacokinetics, fraction exhaled nitric oxide (FENO), estimated right ventricular systolic pressure (eRVSP) measured by echocardiography, and platelet activation were determined. Nebulized sodium nitrite at doses used in this study (37.5 and 75 mg for healthy subjects and 15 mg for HbE/β-thal patients) was well tolerated and did not cause changes in methemoglobin levels and systemic blood pressure. Absorption of inhaled nitrite was rapid with the absolute bioavailability of 18%. In whole blood, nitrite exhibited the dose-independent pharmacokinetics with clearance (CL) of 1.5 l/h/kg, volume of distribution (Vd) of 1.3 l/kg and half-life (t1/2) of 0.6 h. CL and Vd of nitrite was higher in red blood cells (RBC) than whole blood and plasma. HbE/β-thal patients had lower nitrite CL and longer t1/2 in RBC than healthy subjects. FENO increased immediately after inhalation. Following nitrite inhalation, eRVSP remained unchanged but platelet activation was suppressed as evidenced by inhibition of adenosine diphosphate (ADP)-induced P-selectin expression and increase in phosphorylated vasodilator-stimulated phosphoprotein (P-VASPSer239) in platelets. There were no changes in markers of oxidative and nitrosative stress after inhalation. Our results support further development of inhaled nebulized sodium nitrite for treatment of pulmonary hypertension in β-thalassemia.

The Effects of Inhaled Sodium Nitrite on Pulmonary Vascular Impedance in Patients with Pulmonary Hypertension Associated with HFpEF

Purpose The severity and clinical response of pulmonary hypertension (PH) is monitored by measuring pulmonary vascular resistance (PVR). However, PVR is a steady-state measurement and ignores the pulsatile load encountered by the right ventricle (RV), which may be one-third of the total afterload. Pulmonary vascular impedance (PVZ) can depict both steady-state and pulsatile loads, thus may better predict clinical outcomes. We sought to calculate PVZ in patients with PH associated with HFpEF (PH-HFpEF), who were administered inhaled sodium nitrite to better understand the acute effects on afterload. Methods Patients with PH-HFpEF underwent right heart catherization (RHC) to obtain standard hemodynamics, and if eligible, were administered two doses of inhaled sodium nitrite at 45 and 90 mg. Concurrently, transthoracic Doppler spectral imaging was used to measure pulmonary artery velocity. A Fourier transform was used via MATLAB to calculate PVZ at the first ten harmonics for both pre and post-nitrite for comparison. Results Fourteen patients underwent RHC with simultaneous Doppler imaging and received at least one dose of inhaled sodium nitrite. Inhaled sodium nitrite decreased characteristic impedance (Zc, inversely related to compliance), and total work (WT) performed by the RV (Table 1). RV efficiency improved, defined by a reduction in the total work divided by cardiac output (WT/CO). There were trends towards decreases in pulmonary vascular resistance (Z0), first harmonic impedance (Z1), steady state work (Ws), and pulmonary vascular stiffness (Zs) after administration of this drug. Conclusion PVZ analysis showed inhaled sodium nitrite acutely improves pulmonary vascular compliance by reducing characteristic impedance (Zc) more so than PVR (Z0). This was associated with improved RV efficiency and total work. These results suggest inhaled sodium nitrite preferentially acts on the larger proximal compliance vessels to reduce the load on the RV.

Carbonic anhydrase is not a relevant nitrite reductase or nitrous anhydrase in the lung.

Carbonic anhydrase (CA) inhibitors such as acetazolamide inhibit hypoxic pulmonary vasoconstriction (HPV) in humans and other mammals, but the mechanism of this action remains unknown. It has been postulated that carbonic anhydrase may act as a nitrous anhydrase in vivo to generate nitric oxide (NO) from nitrite and that this formation is increased in the presence of acetazolamide. Acetazolamide reduces HPV in pigs without evidence of any NO generation, whereas nebulized sodium nitrite reduces HPV by NO formation; however; combined infusion of acetazolamide with sodium nitrite inhalation did not further increase exhaled NO concentration over inhaled nitrite alone in pigs exposed to alveolar hypoxia. We conclude that acetazolamide does not function as either a nitrous anhydrase or a nitrite reductase in the lungs of pigs, and probably other mammals, to explain its vasodilating actions in the pulmonary or systemic circulations. The carbonic anhydrase (CA) inhibitors acetazolamide and its structurally similar analogue methazolamide prevent or reduce hypoxic pulmonary vasoconstriction (HPV) in dogs and humans in vivo, by a mechanism unrelated to CA inhibition. In rodent blood and isolated blood vessels, it has been reported that inhibition of CA leads to increased generation of nitric oxide (NO) from nitrite and vascular relaxation in vitro. We tested the physiological relevance of augmented NO generation by CA from nitrite with acetazolamide in anaesthetized pigs during alveolar hypoxia in vivo. We found that acetazolamide prevents HPV in anaesthetized pigs, as in other mammalian species. A single nebulization of sodium nitrite reduces HPV, but this action wanes in the succeeding 3h of hypoxia as nitrite is metabolized and excreted. Pulmonary artery pressure reduction and NO formation as measured by exhaled gas concentration from inhaled sodium nitrite were not increased by acetazolamide during alveolar hypoxia. Thus, our data argue against a physiological role of carbonic anhydrase as a nitrous anhydrase or nitrite reductase as a mechanism for its inhibition of HPV in the lung and blood in vivo.

Inhaled nebulized sodium nitrite decreases pulmonary artery pressure in β-thalassemia patients with pulmonary hypertension

Pulmonary hypertension is a life-threatening complication in β-thalassemia. Inhaled sodium nitrite has vasodilatory effect on pulmonary vasculature. However, its effect on pulmonary artery pressure (PAP) in β-thalassemia subjects with pulmonary hypertension has never been reported. In this study, we investigated the change in PAP during inhalation of sodium nitrite in 5 β-thalassemia patients. We demonstrated that sodium nitrite administered by nebulization rapidly decreased PAP as measured by echocardiography and right heart catheterization. The effect of nitrite was short as PAP returned to baseline at end of inhalation. Our findings support acute pulmonary vasodilation effect of nitrite in β-thalassemia with pulmonary hypertension.

Arterial Stiffening With Exercise in Patients With Heart Failure and Preserved Ejection Fraction

BackgroundAortic stiffening and reduced nitric oxide (NO) availability may contribute to the pathophysiology of heart failure with preserved ejection fraction (HFpEF). ObjectivesThis study compared indices of arterial stiffness at rest and during exercise in subjects with HFpEF and hypertensive control subjects to examine their relationships to cardiac hemodynamics and determine whether exertional arterial stiffening can be mitigated by inorganic nitrite. MethodsA total of 22 hypertensive control subjects and 98 HFpEF subjects underwent hemodynamic exercise testing with simultaneous expired gas analysis to measure oxygen consumption. Invasively measured radial artery pressure waveforms were converted to central aortic waveforms by transfer function to assess integrated measures of pulsatile aortic load, including arterial compliance, resistance, elastance, and wave reflection. ResultsArterial load and wave reflections in HFpEF were similar to those in control subjects at rest. During submaximal exercise, HFpEF subjects displayed reduced total arterial compliance and higher effective arterial elastance despite similar mean arterial pressures in control subjects. This was directly correlated with higher ventricular filling pressures and depressed cardiac output reserve (both p < 0.0001). With peak exercise, increased wave reflections, impaired compliance, and increased resistance and elastance were observed in subjects with HFpEF. A subset of HFpEF subjects (n = 52) received sodium nitrite or placebo therapy in a 1:1 double-blind, randomized fashion. Compared to placebo, nitrite decreased aortic wave reflections at rest and improved arterial compliance and elastance and central hemodynamics during exercise. ConclusionsAbnormal pulsatile aortic loading during exercise occurs in HFpEF independent of hypertension and is correlated with classical hemodynamic derangements that develop with stress. Inorganic nitrite mitigates arterial stiffening with exercise and improves hemodynamics, indicating that arterial stiffening with exercise is at least partially reversible. Further study is required to test effects of agents that target the NO pathway in reducing arterial stiffness in HFpEF. (Study of Exercise and Heart Function in Patients With Heart Failure and Pulmonary Vascular Disease [EXEC]; NCT01418248. Acute Effects of Inorganic Nitrite on Cardiovascular Hemodynamics in Heart Failure With Preserved Ejection Fraction; NCT01932606. Inhaled Sodium Nitrite on Heart Failure With Preserved Ejection Fraction; NCT02262078)

Platelet inhibition and increased phosphorylated vasodilator-stimulated phosphoprotein following sodium nitrite inhalation

In the presence of red blood cells (RBCs), nitrite inhibits platelets through its conversion to nitric oxide (NO) by the reductase activity of partially deoxygenated hemoglobin. Inhaled sodium nitrite is being investigated as a therapy for pulmonary hypertension. Here, we measured platelet aggregation, P-selectin expression, platelet-leukocyte aggregates and phosphorylated vasodilator-stimulated phosphoprotein (P-VASPSer239) following sodium nitrite inhalation in healthy subjects. In vitro incubation of nitrite with deoxygenated whole blood showed an increase in P-VASPSer239, which was inhibited by ODQ, a soluble guanylyl cyclase (sGC) inhibitor. Immediately and 60 min after nitrite inhalation, P-VASPSer239 increased in platelets. Platelet aggregation, P-selectin expression, platelet-monocyte and platelet-lymphocyte aggregates decreased after inhalation. In conclusion, sodium nitrite administered to healthy subjects by inhalation can inhibit platelet activation and increase P-VASPSer239 in platelets. Platelet inhibition by nitrite administration may be useful in disorders associated with platelet hyperactivity.

Inhaled Sodium Nitrite Improves Rest and Exercise Hemodynamics in Heart Failure With Preserved Ejection Fraction.

Abnormalities in nitric oxide signaling play a pivotal role in heart failure with preserved ejection fraction (HFpEF). Intravenous sodium nitrite, which is converted to nitric oxide in vivo, improves hemodynamics in HFpEF, but its use is limited by the need for parenteral administration. Nitrite can also be administered using a novel, portable micronebulizer system suitable for chronic use. Determine whether inhaled nitrite improves hemodynamics in HFpEF. In a double-blind, randomized, placebo-controlled, parallel-group trial, subjects with HFpEF (n=26) underwent cardiac catheterization with simultaneous expired gas analysis at rest and during exercise before and after treatment with inhaled sodium nitrite (90 mg) or placebo. The primary end point was the pulmonary capillary wedge pressure during exercise. Before study drug administration, HFpEF subjects displayed an increase in pulmonary capillary wedge pressure with exercise from 20±6 to 34±7 mm Hg (P<0.0001). After study drug administration, exercise pulmonary capillary wedge pressure was substantially improved by nitrite as compared with placebo (baseline-adjusted mean 25±5 versus 31±6 mm Hg; analysis of covariance P=0.022). Inhaled nitrite reduced resting pulmonary capillary wedge pressure (-4±3 versus -1±2 mm Hg; P=0.002), improved pulmonary artery compliance (+1.5±1.1 versus +0.6±0.9 mL/mm Hg), and decreased mean pulmonary artery pressures at rest (-7±4 versus -3±4 mm Hg; P=0.007) and with exercise (-10±6 versus -5±6 mm Hg; P=0.05). Nitrite reduced right atrial pressures, with no effect on cardiac output or stroke volume. Acute administration of inhaled sodium nitrite reduces biventricular filling pressures and pulmonary artery pressures at rest and during exercise in HFpEF. Further study is warranted to evaluate chronic effects of inhaled nitrite in HFpEF. This single center randomized clinical trial is registered at clinicaltrials.gov (NCT02262078).

Comparison of the Relative Propensities of Isoamyl Nitrite and Sodium Nitrite to Ameliorate Acute Cyanide Poisoning in Mice and a Novel Antidotal Effect Arising from Anesthetics

Isoamyl nitrite has previously been considered acceptable as an inhaled cyanide antidote; therefore, the antidotal utility of this organic nitrite compared with sodium nitrite was investigated. To facilitate a quantitative comparison, doses of both sodium nitrite and isoamyl nitrite were given intraperitoneally in equimolar amounts to sublethally cyanide-challenged mice. Righting recovery from the knockdown state was clearly compromised in the isoamyl nitrite-treated animals, the effect being attributable to the toxicity of the isoamyl alchol produced during hydrolysis of the isoamyl nitrite to release nitrite anion. Subsequently, inhaled aqueous sodium nitrite aerosol was demonstrated to ameliorate sublethal cyanide toxicity, when provided to mice after the toxic dose, by the more rapid recovery of righting ability compared to that of the control animals given only the toxicant. Aerosolized sodium nitrite has thus been shown by these experiments to have promise as a better alternative to organic nitrites for development as an inhaled cyanide antidote. The inhaled sodium nitrite led to the production of NO in the bloodstream as determined by the appearance of EPR signals attributable to nitrosylhemoglobin and methemoglobin. The aerosol delivery was performed in an unmetered inhalation chamber, and in this study, no attempt was made to optimize the procedure. It is argued that administration of an effective inhaled aqueous sodium nitrite dose in humans is possible, though just beyond the capability of current individual metered-dose inhaler designs, such as those used for asthma. Finally, working at slightly greater than LD50 NaCN doses, it was fortuitously discovered that (i) anesthesia leads to significantly prolonged survival compared to that of unanesthetized animals and that (ii) the antidotal activity of nitrite anion was completely abolished under anesthesia. Plausible explanations for these effects in mice and their practical consequences in relation to testing putative cyanide antidotes are discussed.

P66: Nebulized inhaled nitrite (AIR001) for pulmonary arterial hypertension: Studies to determine safety, pharmacokinetics, and maximum tolerated dose, lack of pharmacodynamic interaction with sildenafil and optimal nebulizer device

Background Prior work by Bradley et al. [ 1 ] demonstrated single doses of inhaled sodium nitrite up to 125 mg (dose loaded into the nebulizer) were well tolerated and resulted in increased plasma nitrite concentrations, increased exhaled NO, and minimal methemoglobin increases. Thus further clinical development of nebulized sodium nitrite (AIR001) for treatment of pulmonary arterial hypertension (PAH) was planned. Nitrite-generated NO, by acting upon guanylate cyclase is likely to be synergistic with phosphodiesterase type 5 inhibitors (PDE-5i’s), as both increase cGMP and likely would be used concomitantly in PAH patients, thus an interaction study was performed. Clinical trials utilizing AIR001 require a portable, highly efficient nebulizer capable of precise dosing as well as monitoring adherence and compliance which necessitated careful device characterization and tolerance studies. Methods This placebo controlled study of AIR001 was conducted in parts; Parts A, B, and D are reported here. In Part A, ascending doses of AIR001 or placebo from 15 mg to 120 mg (dose loaded into nebulizer) nebulized over 8–10 min every 8 h to cohorts of 8 subjects on days 1–6 to determine maximum tolerated dose (MTD). In Part B, ascending doses of AIR001 were administered at steady state sildenafil (dosed at 20 mg every 8 h), while AIR001 was administered every 6 h (QID). Part D was a randomized, cross-over, open label study to evaluate the pharmacokinetics (PK), safety, and tolerability of AIR001 comparing the Philips I-neb AAD System (Philips Respironics) with the Solo-Idehaler (nebulization head, Aeroneb® Solo (Aerogen, Ltd.), aerosol–reservoir attachment, Idehaler™ (Diffusion Technique Francais)), and the Aeroneb-Go (Aerogen, Ltd). Results In Part A, the MTD was defined at 90 mg (dose loaded into the nebulizer) by expected hemodynamic changes with minimal cough or throat irritation and no significant change in laboratory, spirometric, or electrocardiographic parameters. Plasma nitrite levels were dose dependent with no evidence of accumulation from day 1 to day 6. At the MTD, 90 mg, Cmax was approximately 600 ng/ml (13 μM). Bioconversion to NO resulted in an increase in exhaled NO from 8 ppb predose to 192 ppb. The maximum venous methemoglobin concentration was 2.5%. In Part B, the MTD of 90 mg was well tolerated with no significant effects on systemic blood pressures, or effects on sildenafil PK. In Part D, nitrite PK differences were not statistically significant (p Conclusions Inhaled AIR001 is well tolerated up to doses of 90 mg (loaded dose), and early dose effects are ameliorated upon repeat dosing, both in the absence and presence of sildenafil. Efficacious delivery of AIR001 was demonstrated by the inhalation route and no accumulation of AIR001 was observed. Plasma PK parameters (Cmax at MTD of 10 uM, and half-life of approximately 42 min) lend themselves to application in PAH. Because of precise dosing, adaptive capacity, and its ability to monitor adherence and compliance, the I-neb AAD System is optimal for further study of AIR001 in patients with PAH. Disclosure Dr. Lewis J. Rubin and Dr. Mark T. Gladwin have received support by Aires Pharmaceuticals, Inc.

Inhaled Nitrite Reverses Hemolysis-Induced Pulmonary Vasoconstriction in Newborn Lambs Without Blood Participation

Nitrite can be converted to nitric oxide (NO) by a number of different biochemical pathways. In newborn lambs, an aerosol of inhaled nitrite has been found to reduce pulmonary blood pressure, possibly acting via conversion to NO by reaction with intraerythrocytic deoxyhemoglobin. If so, the vasodilating effects of nitrite would be attenuated by free hemoglobin in plasma that would rapidly scavenge NO. Pulmonary vascular pressures and resistances to flow were measured in anesthetized newborn lambs. Plasma hemoglobin concentrations were then elevated, resulting in marked pulmonary hypertension. This effect was attenuated if infused hemoglobin was first oxidized to methemoglobin, which does not scavenge NO. These results further implicate NO as a tonic pulmonary vasodilator. Next, while free hemoglobin continued to be infused, the lambs were given inhaled NO gas (20 ppm), inhaled sodium nitrite aerosol (0.87 mol/L), or an intravascular nitrite infusion (3 mg/h bolus, 5 mg · kg⁻¹ · h⁻¹ infusion). Inhaled NO and inhaled nitrite aerosol both resulted in pulmonary vasodilation. Intravascular infusion of nitrite, however, did not. Increases in exhaled NO gas were observed in lambs while breathing the nitrite aerosol (≈ 20 ppb NO) but not during intravascular infusion of nitrite. We conclude that the pulmonary vasodilating effect of inhaled nitrite results from its conversion to NO in airway and parenchymal lung tissue and is not dependent on reactions with deoxyhemoglobin in the pulmonary circulation. Inhaled nitrite aerosol remains a promising candidate to reduce pulmonary hypertension in clinical application.