Preparation of Solid Dispersion Using Spray Drying

In the field of drug research, candidate drugs are not easily soluble in water, which is one of the challenges that modern drug formulation researchers often face. Due to the low solubility and low bioavailability of these candidates, people introduced solid dispersion technology to improve the properties of drug compounds that are difficult to dissolve in water. Solid dispersion refers to a dispersion system formed by uniformly dispersing drugs in a certain solid carrier material in the form of molecular, amorphous, and microcrystalline. Spray drying is a relatively common technique for the preparation of solid dispersion.Preparation-of-Solid-Dispersion-Using-Spray-Drying 3

Preparation of solid dispersion using spray drying — the relationship

The spray drying means that the drug and the carrier are dissolved in a solvent and atomized into a dry gas. After the solvent evaporates, dry particles are formed. It is a method that can produce solid products from a liquid in the form of a solution or suspension, and its application has greatly improved the bioavailability of poorly soluble compounds.

Preparation of solid dispersion using spray drying — the working process

The liquid enters the nozzle to be atomized, the generated droplets are mixed with the dry gas, the solvent in it evaporates, and finally, the particles are separated from the dry gas. This powder dryer machine is very fast drying equipment because it generates fine droplets and has a high specific surface area. There are different devices for spray drying. Although the atomization device and atomization force are not the same, most of the components are similar. For the preparation of solid dispersion, the polymer and the poorly soluble drug are generally dissolved in a suitable solvent and then spray-dried to make the drug highly dispersed in the polymer in an amorphous state.

Preparation of solid dispersion using spray drying — the working principle

There is more than one application of spray drying in pharmaceutical industry. For all of its applications, you shall know its working principle.

Spray drying tech dries liquid materials into powder, and the drying process can be divided into 3 stages:

(1) Use an atomizer to atomize the liquid to form many small droplets;

The feed solution and atomizing gas are respectively fed into an atomizing device, and then the liquid is atomized at the tip of the nozzle to form liquid filaments and finally into fine droplets. The atomizer is the core device in the spray drying process, and its function is to disperse the liquid into fine droplets.

(2) When the droplets are in direct contact with the dry hot air, the solvent evaporates quickly to form dry particles;

After the droplets are formed, they enter the spray drying machine and come into direct contact with hot air. The droplets in the drying chamber are in contact with the drying gas at a certain temperature, and the solvent components in the droplets evaporate until a solid product is formed.

(3) Separate and collect dry particles

Finally, the dried particles are separated from the drying gas in a separator and collected in a receiving container. Commonly used devices for collecting dried products in spray drying include cyclone separators and bag filters.

Preparation of solid dispersion using spray drying — summary

In the modern pharmaceutical industry, the use of spray drying to prepare solid dispersion provides an effective solution to the oral bioavailability of poorly soluble drugs. The spray drying can prepare micron or even nanometer-level solid dispersion powders. It is an effective technique to improve the solubility of poorly soluble drugs and is especially suitable for heat-sensitive drugs.

The tech of spray drying has the advantages of rapid, economical, and is suitable for particle engineering and thermally unstable materials. The disadvantage is that depending on the type of solvent, a relatively high temperature may be used for drying, and in order to ensure uniform and effective drying of the spray, the concentration of the solution is usually required to be relatively small, so a large amount of organic solvent needs to be consumed, which will significantly increase the process cost and equipment cost, etc. However, with the progress of science and technology, the technical problems will be gradually solved , and many more applications of spray drying in pharmaceutical industry will be known by us.