Bioavailability Enhancement of Poorly Soluble Drugs: The Holy Grail in Pharma Industry

Background:

Bioavailability, one of the prime pharmacokinetic properties of a drug, is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation and is used to describe the systemic availability of a drug. Bioavailability assessment is imperative in order to demonstrate whether the drug attains the desirable systemic exposure for effective therapy. In recent years, bioavailability has become the subject of importance in drug discovery and development studies.

Methods:

A systematic literature review in the field of bioavailability and the approaches towards its enhancement have been comprehensively done, purely focusing upon recent papers. The data mining was performed using databases like PubMed, Science Direct and general Google searches and the collected data was exhaustively studied and summarized in a generalized manner.

Results:

The main prospect of this review was to generate a comprehensive one-stop summary of the numerous available approaches and their pharmaceutical applications in improving the stability concerns, physicochemical and mechanical properties of the poorly water-soluble drugs which directly or indirectly augment their bioavailability.

Conclusion:

The use of novel methods, including but not limited to, nano-based formulations, bio-enhancers, solid dispersions, lipid-and polymer-based formulations which provide a wide range of applications not only increases the solubility and permeability of the poorly bioavailable drugs but also improves their stability, and targeting efficacy. Although, these methods have drastically changed the pharmaceutical industry demand for the newer potential methods with better outcomes in the field of pharmaceutical science to formulate various dosage forms with adequate systemic availability and improved patient compliance, further research is required.

The Solubility-Permeability Trade-Off of Progesterone With Cyclodextrins Under Physiological Conditions: Experimental Observations and Computer Simulations

This study intended to evaluate the effect of cyclodextrins on the apparent solubility and permeability of lipophilic drugs under physiological conditions and establish in silico model to choose the optimal amount of cyclodextrins for cyclodextrin-containing oral formulations. In order to study the effect of cyclodextrins under physiological conditions, bile salts and lecithin were added into the rat intestinal perfusion solution to simulate the fasted intestinal fluid. In addition, the in vivo oral absorption performances of cyclodextrin-containing formulations were simulated by gastrointestinal simulation technology based on the advanced compartmental absorption and transit model. The permeability of progesterone was not significantly different between 0.1 mM and 1 mM of 2-hydroxypropyl-β-cyclodextrins (HP-β-CD) under physiological conditions. When the concentration of HP-β-CD was 1 mM, the permeability of progesterone under physiological conditions was significantly higher than that in vitro. The in silico model established in this study was validated by in vivo studies of 4 formulations containing different dosage of cyclodextrin, proving that it was accurate and reliable. In conclusion, this work that demonstrates the permeability of lipophilic drugs could not decrease quickly among a certain range of dosage of HP-β-CD in vivo. Studying the solubility-permeability interplay under physiological conditions would be more meaningful.