The lipid formulation classification system: characteristic features, advantages, and disadvantages of the four essential types of “lipid” formulations.
Formulation type
Material
Characteristics
Advantages
Disadvantages
Type I
Oils without surfactants (e.g., tri-, di-, and monoglycerides)
Nondispersing requires digestion
Generally recognized as safe (GRAS) status; simple; and excellent capsule compatibility
Formulation has poor solvent capacity unless drug is highly lipophilic
Type II
Oils and water insoluble surfactants
SEDDS formed without water-soluble components
Unlikely to lose solvent capacity on dispersion
Turbid o/w dispersion (particle size 0.25–2 m)
Type III
Oils, surfactants, and cosolvents (both water-insoluble and water-soluble excipients)
SEDDS/SMEDDS formed with water-soluble components
Clear or almost clear dispersion, drug absorption without digestion
Possible loss of solvent capacity on dispersion, less easily digested
Type IV
Water-soluble surfactants and cosolvents
Formulation disperses typically to form a micellar solution
Formulation has good solvent capacity for many drugs
Likely loss of solvent capacity on dispersion may not be digestible