Page 33 - Drug Discovery and Development: Prospects and Challenges

Drug Discovery and Development: Prospects and Challenges / 23

Brothers and sisters,
Ladies and Gentlemen,

Drug Formulation

Formulation is an important step in drug discovery. It provides a material
for preclinical pharmacokinetic, efficacy and toxicological studies
(Strickley, 2008). It is widely acknowledged that new medications would
exhibit certain formulation constraints, such as solubility problems. The
Biopharmaceutical Classification System (BCS) is an experimental
technique to determine the permeability and solubility of a particular
product under controlled settings. Based on their aqueous solubility
and intestinal permeability, the drugs are classified into four classes.
In addition to the BCS classification, the input from pre-formulation
studies would benefit the formulation by providing a detailed solubility
profile, polymorph status, intended dosage form, target dose, dosing
schedule, drug stability, excipient compatibility, and understanding of
the transporter and metabolic pathways.
Drugs in BCS are classified as high permeability but low solubility.
In order to improve the performance of these drugs, a special technique
is required to increase the surface area, such as particle size reduction,
using a solid solution, or solid dispersion. Nowadays, new technologies
are available to modify the formulation using solvents and/or surfactants.
One of the strategies is to encapsulate the drugs with Nanotechnology
Drug Delivery System (NDDS) (Figure 20). NDDS refers to a material
that has at least one dimension that falls under the nanometer scale (1–100
nm) or is made with basic units in three-dimensional space (Deng, 2020).
Nanotechnology has become a useful tool to regulate the delivery rate
and target the drug delivery to a specific location, such as using vesicle
nanocarrier, for instance, liposomes and niosomes. Liposome comprises
cholesterol and phospholipid, while niosome uses cholesterol and non-
ionic surfactant. The active principle in liposomes and niosome involves
the encapsulation of the drug in vesicle components of hydrophilic and
hydrophobic areas. Niosome (Figure 21) is made up of bilayer structures
and formed by self-association of non-ionic surfactant and cholesterol