Spray Drying as an Enabling Technology for Inhalation Drug Delivery


A carrier-primarily based system strategy is widely known by the inhalation community. Novel method necessities, which include the transport of poorly water-soluble compounds, biomolecules, and excessive dosages to the lungs, but, are not easily met via the conventional strategy. For this reason, spray-drying has received hobby as an allowing generation for inhalation drug delivery, culminating in more and more merchandise on the market.

In this text, using spray-drying as a platform for tailor-made dry powder inhaler (dpi) system in combination with disposable devices will be explored, for amorphous composite particles with improved traits and performance, for a diverse variety of doses and applications. The main blessings of this manufacturing method for inhalation drug transport can be discussed in element in addition to the manufacturing demanding situations and important method parameters to think about whilst developing a spray-dried dpi, from particle engineering to device filling.

Pulmonary shipping is a well-researched, non-invasive technique for local and systemic drug shipping of apis. The lungs have precise capabilities, along with big surface area, thin alveolar capillary membrane, low enzymatic interest, and absence of first-pass metabolism, making this course of administration appealing for drug transport (1). Even though there are 3 foremost techniques to reach delivering pills to the lung (nebulizers, metered-dose inhalers, and dry powder inhalers [DPIs]), dpis allow for a direct delivery with out propellants.

Dpis are a aggregate of device and dry powder able to handing over, upon patient breathing, apis to the lung surface. To accomplish this shipping, the device should ensure green particle aerosolization, and the components have to have suitable aerodynamic properties. Among dpis, carrier-based totally formulations are the maximum famous and established. Those formulations include a bodily combination of massive service particles and micronized api with optimized length and morphology (2). Best particles of excipients might be brought to those mixtures to enhance the aerodynamic overall performance of the drug product.

Service-based totally system challenges
Service-based totally drug merchandise gift some benefits, specifically advanced balance due to the dry crystalline state and a robust manufacturing method. Those formulations, however, have some drawbacks, which include an inefficient drug deposition inside the deep lung; in reality, it’s miles expected that most effective 10–15% of the drug administered reaches the deep lung, as approximately 20% of the drug administered is misplaced within the oropharyngeal tract and the remaining percentage isn’t always launched from the service (2, 3). Transport performance is especially hindered on the shipping of higher dosages; because the drug load inside the combination increases, the aerodynamic performance decreases, proportionally (4). Any other issue of these formulations is the lack of ability to behave as a solubility enhancer for poorly water-soluble compounds; it isn’t always the main cause of service-based formulations to adjust or improve the surface of the api and consequently, its dissolution fee. Lastly, carrier-primarily based formulations require a micronization step, which makes its applicability to touchy compounds, inclusive of biopharmaceuticals, challenging. The molecular weight of biologic molecules under development for inhalation tiers from some kda to about 50 kda. Large molecules present elevated problems whilst growing a system for inhalation, given the multiplied probability of chemical and bodily balance challenges (five).

Role of particle engineering
A new system approach exhibits a promising and revolutionary manner of increasing the pulmonary deposition of medication. Spray drying (sd) is the gold standard particle engineering era generally hired within the manufacturing of engineered debris wherein the api is on my own or embedded within an excipient matrix (6). Sd allows the production of inhalable powders with multiplied manipulate over particle size, morphology, and density via great-tuning formulation composition and process parameters.

Particle engineered formulations produced by way of sd have an optimized aerodynamic performance, leading to an extended excellent particle fraction (fpf), meaning a higher shipping to the deep lungs. The optimized performance of provider-loose particles is because of the intentional particle layout, in addition to higher powder uniformity and aerosolization (three). Particle design upon sd is achieved by using the association of substances with one-of-a-kind roles in the identical electricity, and with the aid of adjusting the sd technique parameters, leading to exclusive particle morphologies and interactions. Hence, the sd technology permits a reduction of the api concentration in the system while preserving the quantity introduced to the goal (7). Moreover, amorphous strong dispersions synthetic by sd are notably used for solubility enhancement for other shipping routes and feature proven comparable effects on pulmonary delivery (8). Any other sd application is the stabilization and effective pulmonary transport of biopharmaceuticals inside composite engineered particles, while preventing product denaturation at excessive temperatures because of the flash-drying phenomenon (5).

Demanding situations for the duration of composite debris improvement
In spray drying, both a feed answer and suspension may be processed. The feed is atomized in a nozzle into a great spray that is typically flash dried by way of a co-cutting-edge stream of hot nitrogen. The particles, once formed, are collected in cyclones and/or bag filters and the drying fuel recycled after condensing the removed solvent.

There are a limited number of excipients suitable for lung delivery, and excipient desire is driven via stabilization of the api, which translates into stabilizing the amorphous shape of an api or decreasing the mobility of a biomolecules, development of method dispersibility by adding a shell former to maximise aerodynamic performance, and, if required, permeability enhancement via adding a lipid as an example (three). Consequently, to take advantage of the sd era for the duration of the training of composite debris for inhalation, it’s miles obligatory to carry out ok excipient selection (nine).

The sd technique permits the production of inhalable debris with managed particle size, water content material, morphology, and density by way of tuning no longer simplest the system composition, however additionally the system parameters. There are numerous phenomena to think about in the sd process: the atomization this is key for figuring out the droplet length and in a while the particle length; the particle formation, with the method drying kinetics impacting particle size and morphology; the general fluid dynamics across the device, dictating drying efficiencies and average yields at the collector, as well as the overall procedure (3,8). Adequate technique improvement and adjustment of manner parameters allow a good manage inside the powder characteristics and an improvement of powder uniformity, dispersibility and, therefore, aerosolization behavior. This manner development in the end consequences in a drug product with an augmented introduced dose to the lungs, without increasing the emitted dose, which advantages the overall safety of the drug product with a discount within the adverse facet results experienced by patients with respiration illnesses. Furthermore, from the manufacturer’s point of view, sd era represents an smooth to operate, bendy, effortlessly scalable, and time-powerful era (nine).

Case have a look at
As a case examine, keep in mind the dpi improvement of a synthetic peptide ap301 (solnatide) designed to prompt the epithelial sodium channel (enac) of kind ii alveolar cells of lungs. Solnatide calls for a excessive dosage delivery to clear pulmonary edema bobbing up, as an instance, from excessive altitude publicity, blood transfusions, or lung infections (e.G., pneumonia and influenza) (10).

The sd system development centered a drug-by myself product (i.E., freed from extra excipients) suitable for lung delivery. The aim become to attain one-of-a-kind particle size distributions (psd) aiming to reduce the adhesive/cohesive forces which might be usually found in composite debris.

A disposable, prefilled tool (twinmax, hovione), which become designed to handle high dosage transport of challenging powders, was used (see parent 1). Three device prototypes had been studied, with the goal of maximizing the dispersive forces and powder deagglomeration. A prefilled tool (in preference to a pill-based dpi) is an advantage for rescue/emergency remedies. Because the tool is prefilled, the cohesive/adhesive stability ought to be excellent-tuned and optimized to have lower adhesion to the device as well as lower attachment to the coarse lactose, aiming for an accelerated high-quality particle mass (fpm).

The engineered particles were synthetic using a büchi unit version b-290 superior, by means of spraying a solution of the api (ap301) in water. The atomization ratio was optimized to refine the psd and to optimize the cohesive-adhesive stability among particles and gadgets’ floor (see desk i).

The results in desk i show that the manipulation of the ratio of atomization allowed a nice manipulate of the psd (with all dv50 values comprised between 2 and 3 μm). All powders were located to be amorphous, with a completely excessive purity and a low water content (kf < five%). All powders provided bioactivities comparable with the beginning uncooked fabric (srm), indicating the sd procedure does not cause degradation or lack of function.
The batches acquired were characterised in phrases of their aerodynamic overall performance using an andersen cascade impactor, with twinmax prototypes running at ~40 l/min for four kpa. The parameters analyzed were emitted mass (em) (mg) and fpm (mg). A total of three replicates were achieved to symbolize the chosen combinations of powder and tool shown in determine 2.

The results display that the approach of improving the aerodynamic performance through particle size manipulation changed into fruitful. Evaluating batch 1, 2 and 3 crammed in twinmax, a dependency of aerodynamic performance on particle size may be found; batch 2 (larger particles, dv90 of five.9 µm) bring about a dpi with a appreciably better em, whilst the closing formulations gift a better retention on the device surfaces upon actuation. Moreover, fpf is inferior for batch 1 (smaller particles, dv90 of 3.Nine µm). This result can be defined via the growth of surface area with the decrease of particle size, leading to greater sizable particle agglomeration, and extra power required to deagglomerate. It’s far vital to word all batches are within the inhalable range, and the dependency is expected to be inverse for larger particle sizes, because the fpm could decrease. Evaluating the outcomes of the batch 3 filled into the three prototypes, prototype 1 provides superior overall performance. The combination of batch 3 and twinmax 1, with a dv90 of four.9 μm, yielded an em of 80 mg (a 15% boom when as compared with batch 1). General, those results endorse that a compromise between psd, em, and fpm need to be taken into consideration, considering better psd cause better em but, in trendy, to decrease fpm on account of a specific balance among cohesive and adhesive forces. Moreover, twinmax 1 was the maximum promising tool, with a fpm above 30 mg, that is a excessive result thinking about the prototype nature of the tool.

In conclusion, sd technology permits the production of inhalable particles with advanced characteristics, including managed particle length, morphology, and density. This control is feasible thru best-tuning of method composition and optimization of technique parameters, together with the solvent machine, solute awareness, atomization, feed flowrate, drying fuel charge, and others.

The protein ap301 spray-dried powder in mixture with the twinmax device indicates how sd may be carried out to layout a high-dosage, stable dpi containing a biopharmaceutical, with adequate aerodynamic overall performance and with out affecting the molecule bioactivity.


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About the authors
Susana saldanha, pharmd, and beatriz fernandes, msc, are each system improvement scientists at hovione. João ventura, phd, is director of generation development and licensing at hovione technology.

Article info
Pharmaceutical technology
Vol. Forty five, no. 7
July 2021
Pages: 36–40

Whilst relating to this text, please cite it as s. Saldanha, b. Fernandes, and j. Ventura, “spray drying as an permitting era for inhalation drug delivery,” pharmaceutical generation forty five (7) 2021.