Characterization of heparin aerosols generated in jet and ultrasonic nebulizers

Targeted, Site-Specific, Delivery Vehicles of Therapeutics for COVID-19 Patients. Brief Review

Definitive pharmacological therapies for COVID-19 have yet to be identified. Several hundred trials are ongoing globally in the hope of a solution. However, nearly all treatments rely on systemic delivery but COVID-19 damages the lungs preferentially. The use of a targeted delivery approach is reviewed where engineered products are able to reach damaged lung tissue directly, which includes catheter-based and aerosol-based approaches. In this review we have outlined various target directed approaches which include microbubbles, extracellular vesicles including exosomes, adenosine nanoparticles, novel bio-objects, direct aerosol targeted pulmonary delivery and catheter-based drug delivery with reference to their relative effectiveness for the specific lesions. Currently several trials are ongoing to determine the effectiveness of such delivery systems alone and in conjunction with systemic therapies. Such approaches may prove to be very effective in the controlled and localized COVID-19 viral lesions in the lungs and potential sites. Moreover, localized delivery offered a safer delivery mode for such drugs which may have systemic adverse effects.

A Pilot Study of Nebulized Heparin for Prevention of Ventilator Induced Lung Injury: Comparative Effects with an Inhaled Corticosteroid

Background:

Ventilator-induced lung injury (VILI) is a side effect of mechanical ventilation. Lung inflammation and pulmonary activation of coagulation are induced by mechanical stress. Clinical and preclinical studies show that heparin possesses anti-inflammatory properties. Therefore, we assessed the effects of nebulized heparin in VILI.

Methods:

Sixty critically ill adult patients who require mechanical ventilation for more than 48 h were included in this prospective, nonrandomized controlled study. Patients received nebulized heparin (10,000 U every 6 h) for 5 days. The matched control group received nebulized budesonide as routine practice in our center. This study assessed changes in partial pressure of oxygen to inspired fraction of oxygen ratio (PaO₂/FiO₂) and rapid shallow breathing index (RSBI) during the study as primary endpoints.

Results:

The average daily PaO₂/FiO₂ ratio was not statistically significant between both groups (187 ± 11.6 vs. 171 ± 11.6, P = 0.35). The RSBI also did not differ between groups (P = 0.58). Heparin administration was associated with a higher number of ventilator-free days among survivors but not significantly (7.7 ± 10.6 vs. 5.1 ± 8, 95% confidence interval − 2.2–7.5, P = 0.28). Successful weaning from mechanical ventilation was higher in the heparin group (P = 0.42). We did not observe any serious or increased adverse effects from nebulized heparin.

Conclusion:

The results of this study show that the overall effectiveness of nebulized heparin is at least as comparable with a potent corticosteroid (budesonide). Heparin could be a safe and effective modality for patients who at risk of VILI.

Nebulized heparin for patients under mechanical ventilation: an individual patient data meta-analysis

Pulmonary coagulopathy is a characteristic feature of lung injury including ventilator-induced lung injury. The aim of this individual patient data meta-analysis is to assess the effects of nebulized anticoagulants on outcome of ventilated intensive care unit (ICU) patients. A systematic search of PubMed (1966-2014), Scopus, EMBASE, and Web of Science was conducted to identify relevant publications. Studies evaluating nebulization of anticoagulants in ventilated patients were screened for inclusion, and corresponding authors of included studies were contacted to provide individual patient data. The primary endpoint was the number of ventilator-free days and alive at day 28. Secondary endpoints included hospital mortality, ICU- and hospital-free days at day 28, and lung injury scores at day seven. We constructed a propensity score-matched cohort for comparisons between patients treated with nebulized anticoagulants and controls. Data from five studies (one randomized controlled trial, one open label study, and three studies using historical controls) were included in the meta-analysis, compassing 286 patients. In all studies unfractionated heparin was used as anticoagulant. The number of ventilator-free days and alive at day 28 was higher in patients treated with nebulized heparin compared to patients in the control group (14 [IQR 0-23] vs. 6 [IQR 0-22]), though the difference did not reach statistical significance (P = 0.459). The number of ICU-free days and alive at day 28 was significantly higher, and the lung injury scores at day seven were significantly lower in patients treated with nebulized heparin. In the propensity score-matched analysis, there were no differences in any of the endpoints. This individual patient data meta-analysis provides no convincing evidence for benefit of heparin nebulization in intubated and ventilated ICU patients. The small patient numbers and methodological shortcomings of included studies underline the need for high-quality well-powered randomized controlled trials.

The function and performance of aqueous aerosol devices for inhalation therapy

OBJECTIVES

In this review paper, we explore the interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations for several types of devices, namely jet, ultrasonic and vibrating-mesh nebulizers; colliding and extruded jets; electrohydrodynamic mechanism; surface acoustic wave microfluidic atomization; and capillary aerosol generation.

KEY FINDINGS

Nebulization is the transformation of bulk liquids into droplets. For inhalation therapy, nebulizers are widely used to aerosolize aqueous systems, such as solutions and suspensions. The interaction between the functioning mechanism of different nebulizers and the physicochemical properties of the formulations plays a significant role in the performance of aerosol generation appropriate for pulmonary delivery. Certain types of nebulizers have consistently presented temperature increase during the nebulization event. Therefore, careful consideration should be given when evaluating thermo-labile drugs, such as protein therapeutics. We also present the general approaches for characterization of nebulizer formulations.

SUMMARY

In conclusion, the interplay between the dosage form (i.e. aqueous systems) and the specific type of device for aerosol generation determines the effectiveness of drug delivery in nebulization therapies, thus requiring extensive understanding and characterization.

Jet and ultrasonic nebulization of single chain urokinase plasminogen activator (scu-PA)

Recent studies have indicated that the deposition of intra-alveolar fibrin may play a central role in the pathogenesis of acute respiratory distress syndrome (ARDS). Our aim was to study whether the indigenous fibrinolytic agent (urokinase) normally present in the alveoli can be administered locally by nebulization in a recombinant zymogen form as single chain urokinase plasminogen activator (scu-PA). We aimed to characterize the particle size distribution, drug output, and enzymatic activity of scu-PA after nebulization with a Ventstream jet nebulizer (Medic-Aid, Bognor Regis, UK) and a Syst'AM DP-100 ultrasonic nebulizer (Pulmolink, Kent, UK). The particle size distribution was measured with a laser diffraction method and the drug output was determined by collection on filters. The amount of protein on the filters was determined with the Lowry method, and the enzymatic activity after nebulization was measured with a microtiter fibrin plate assay. The mass median diameter (MMD) of the scu-PA aerosol generated with the ultrasonic nebulizer was 3.69 (3.53-3.83) microm and with the jet nebulizer 2.96 (2.91-3.03) microm (p < 0.001). The drug output from the two nebulizers did not differ between nebulizers (p = 0.054). Fibrinolytically active scu-PA was generated with both nebulizers, but in contrast to jet nebulization, ultrasonic nebulization caused partial inactivation of scu-PA (p < 0.001). In conclusion, nebulization of scu-PA with the jet nebulizer is superior to ultrasonic nebulization in terms of particle size distribution and preservation of fibrinolytic activity.

Lung deposition and clearance of inhaled (99m)Tc-heparin in healthy volunteers

The purpose of this study was to quantify the lower respiratory tract (LRT) dose delivered by a single nebulization of (99m)technetium-labeled sodium heparin as well as its airway distribution, and kinetics of aerosol clearance, since inhaled heparin may be useful in the treatment of asthma. Fifteen healthy subjects (5 male, 10 female) inhaled heparin from a jet nebulizer loaded with 90,000 IU of (99m)Tc-heparin, driving flow rate 10 L/min. Lung scintigrams and blood samples were taken immediately and at several time points up to 24 h after inhalation. 15 +/- 3% (mean +/- SD) (mean 13,300 IU) of the heparin nebulizer charge reached the mouth, and 8 +/- 2% (mean 7,000 IU) was found in the LRT. Jet nebulizer residual was 48 +/- 6% (mean 43,000 IU), 32 +/- 4% (mean 29,000) was found on exhalation filters, and 5 +/- 2% in the tubing. (99m)Tc-heparin was distributed uniformly in the lungs, and clearance was biphasic. 39 +/- 8% of the LRT dose of (99m)Tc-heparin remained in the lungs 24 h after inhalation. 10.00 +/- 3.40% (687 +/- 310 IU) of the LRT dose or 0.76 +/- 0.35% of the nebulizer charge was found in the blood. Peak concentration in the blood was found 61 +/- 25 min after conclusion of inhalation, which took 15 min. We conclude that a small but significant fraction of nebulized heparin reaches the LRT. The inhaled heparin distributes uniformly in the lungs from which it clears slowly, making it suitable for local administration without induction of measurable changes in coagulation assays. Administration of the present single dose of heparin thus appears to be safe.