Abstract
Many active pharmaceutical ingredients (APIs) exhibit poor solubility and low dissolution rates in aqueous environments such as the luminal fluids of the gastrointestinal tract. The oral bioavailability of these compounds is usually very low as a result of their poor solubility properties. In order to improve the bioavailability of these poorly soluble drugs, formulation strategies have been applied as a means to improve their aqueous solubility and dissolution rates. With respect to formulation approaches, excipients can be incorporated in the formulation to assist in the dissolution process of the drug, or specialized dosage forms can be formulated that improve dissolution rate through various mechanisms. This paper provides an overview of selected excipients (e.g., alkalinizing agents, surfactants and sugars) that can be used in formulations to increase the dissolution rate as well as specialized dosage forms such as self-emulsifying delivery systems and formulation techniques such as inclusion complexes and solid dispersions. These formulation approaches are discussed with available examples with specific reference to positive outcomes in terms of drug solubility and bioavailability enhancement.
Highlights
Active compounds or drugs are usually not administered to patients on their own as single compounds, but are formulated into carefully designed dosage forms
The in vivo bioavailability results were in agreement with the dissolution results, which showed that a Cmax value of 45.38 ng/mL could be reached with the SNEDDS formulation, while only 23.95 ng/mL was obtained for the commercial tablet suspension, revealing a 1.89-fold increase in Cmax for the SNEDDS [50]
Several studies have shown that different classes of functional excipients have a definite and beneficial effect on the solubility/dissolution and the bioavailability of poorly soluble active pharmaceutical ingredients (APIs)
Summary
Active compounds or drugs ( referred to as active pharmaceutical ingredients; APIs) are usually not administered to patients on their own as single compounds, but are formulated into carefully designed dosage forms. The functions of excipients in dosage forms are related to all the different aspects of the final product including its manufacturability, the stability of the API, dose uniformity, effective delivery of the API to the systemic circulation after administration as well as acceptable organoleptic properties for maximum compliance by the patient [2]. Approximately 90% of newly discovered therapeutic compounds, which are in the development phase, have been reported to exhibit poor aqueous solubility For these drugs, functional excipients are needed to assist in overcoming their poor physico-chemical properties. Formulation strategies that have been investigated for the same purpose include melt extrusion/granulation, formation of solid dispersions and formation of inclusion complexes Excipients such as surfactants, polymers, super-disintegrants and multifunctional fillers have been included in dosage forms to increase the apparent solubility of drugs [11,12]. Excipients Added to Solid Oral Dosage Forms to Improve Drug Solubility and/or Dissolution
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