Principles, Applications and Limitations of the Liquisolid System of Drug Delivery: A Review

The liquisolid system of drug delivery continues to find usefulness as a potent means to circumvent solubility and dissolution challenges commonly encountered during drug formulation and medicine development in the pharmaceutical industry. Originally invented by Spireas, the technique has gained acceptance and improved over the years, in the types of excipients used, nature and class of drug formulated and its applications not only in transforming lipophilic and poorly soluble drugs to solid dosage forms with enhanced bioavailability, but also now gaining popularity in modified delivery, photoprotection and minimizing the effect of pH on drug release. This review thus highlights the foundational principles of the liquisolid technique, examines current methods employed and modern applications of this technique. It also gives present knowledge of this delivery technique and its limitations. A systematic approach to the search of published literature in standard databases (Pubmed, Google Scholar, Researchgate) was carried out using specific search terms and operators that provided available works as information sources for this review. Critical evaluation of obtained literature from the database was adopted to extract data on the principles and current applications of the liquisolid systems beyond its intended initial use. The prevailing mechanism for enhancing bioavailability via the technique is improved wetting and drug presentation in well dispersed or soluble state; minimal pH influence is based on the phenomenon of saturation solubility of the drug in the nonvolatile vehicle; and photoprotection is due to high refractive and diffraction capacities of the coating materials used. This work concludes by presenting the identified and potential limitations of the liquisolid technique. It gives expert opinions on how these are being circumvented and future perspectives on this ever-unfolding promising drug delivery strategy. It will be an invaluable contribution to current literature in drug development research employing liquisolid techniques for drug delivery.