An Update of Moisture Barrier Coating for Drug Delivery

Abstract

Drug hydrolytic degradation, caused by atmospheric and inherent humidity, significantly reduces the therapeutic effect of pharmaceutical solid dosages. Moisture barrier film coating is one of the most appropriate and effective approaches to protect the active pharmaceutical ingredients (API) from hydrolytic degradation during the manufacturing process and storage. Coating formulation design and process control are the two most commonly used strategies to reduce water vapor permeability to achieve the moisture barrier function. The principles of formulation development include designing a coating formulation with non-hygroscopic/low water activity excipients, and formulating the film-forming polymers with the least amount of inherent moisture. The coating process involves spraying organic or aqueous coating solutions made of natural or synthetic polymers onto the surface of the dosage cores in a drum or a fluid bed coater. However, the aqueous coating process needs to be carefully controlled to prevent hydrolytic degradation of the drug due to the presence of water during the coating process. Recently, different strategies have been designed and developed to effectively decrease water vapor permeability and improve the moisture barrier function of the film. Those strategies include newly designed coating formulations containing polymers with optimized functionality of moisture barrier, and newly developed dry coating processes that eliminate the usage of organic solvent and water, and could potentially replace the current solvent and aqueous coatings. This review aims to summarize the recent advances and updates in moisture barrier coatings.

Pharmaceutical Application of Tablet Film Coating

“…Organic solvent-based film coating: Although the use of organic solvent is not preferred, film coating with hydrophobic or lipophilic polymers requires the use of organic solvents due to the low aqueous solubility of coating materials. The highly hydrophobic polymers are beneficial as moisture-protective coating polymers as they can reduce the water vapor permeability of the final film by preventing the movement of water molecules [ 9 ]. In addition, coating process using organic solvents can also reduce drug degradation by hydrolysis.…”

“…Therefore, organic solvent-based coating is useful for moisture sensitive drugs. The rate of evaporation of the solvent is crucial for the quality of final product and many variables including temperature, atmospheric pressure, and air movement should be adjusted to optimize the evaporation rate [ 9 ]. Despite of pharmaceutical needs, organic solvent-based coating has many critical limitations because of potential toxicity of residual solvents, flammability, and environmental safety issues [ 10 ].…”

Aqueous Film Coating the Current Trend

“…Since, water-soluble polymers do not influence therapeutic effect or drug release, thus widely employed in moistureprotective coating 31 , while some could be used for tastemasking coating and can be easily used in AFC process 20 .…”

Lipid-Polymeric Films: Composition, Production and Applications in Wound Healing and Skin Repair

“…Lipophilic films are generally applied onto the skin to exploit their moisture barrier properties [ 50 ]. Due to their nonpolar nature, the incorporation of a lipid into a polymeric film can make it even more lipophilic [ 51 ].…”