Dry Powder Inhaler of Sustained-Release Microspheres Containing Glycyrrhizin: Factorial Design and Optimization

Glycyrrhizin is a saponin glycoside of the liquorice plant. It is commonly used to treat respiratory problems. Inhalable glycyrrhizin formulation in asthma can be a good alternative for widely used inhaled corticosteroids that exhibit side effects upon long-term use.

Asthma is a major and prevalent respiratory disease. However, the rate of drug development in this arena is quite slow, as indicated by merely four new drugs approved by the USFDA in the last 6 years for respiratory diseases.

We herein propose to design and develop Glycyrrhizin-inhalable microspheres for the treatment of asthma.

A 3² full factorial design was applied to show the effect of the two independent variables (polycaprolactone, and polyvinyl alcohol concentration) on each of the selected dependent variables (drug loading and entrapment efficiency).

The optimized microspheres were spherical and 1-5 μm in size. The formulation showed a fine particle fraction of 78%, indicating that the powders were suitable for inhalation. The Drug loading and encapsulation efficiency of the optimized formulation were found to be 9.8% and 40.98%, respectively. The aerosolization study on the Anderson cascade impactor showed that deposition of particles of formulation blended with lactose was better than nonblended formulation and drug in the lungs.

In comparison to the pure drug, optimized formulation prolonged drug residency in the lung for more than 12 hrs after inhalation. Inhalable microparticles of glycyrrhizin provide sustained and prolonged drug release in the lungs along with protection of drugs against pulmonary degradation.