Biphasic liquid dosage forms contain two immiscible phases, a dispersed solid or liquid phase within a continuous liquid phase. Suspensions and emulsions are examples. They are used to deliver drugs that are poorly soluble and allow inclusion of multiple incompatible ingredients. Compared to monophasic forms, biphasic forms contain distinct phases rather than a single homogeneous phase. They exhibit higher bioavailability than other dosage forms but are also bulkier and more costly to produce.

1. Biphasic liquid dosage forms:
It is a liquid dosage form is one that has two phases; suspensions and
emulsions are two examples of biphasic liquid dosage forms.
A biphasic system consists of a solid dispersed state and a liquid
continuous phase that can be aqueous or oily and is stabilized by the
addition of a suspended agent.
These are commonly taken orally or through the parenteral route, and
they are also used for external applications.
It is used when the drugs are poorly soluble in the solvent.
Drugs can be either liquid or solid from the dispersed phase of the
system,
when the solid drug is distributed in the dispersion medium; the
formed system is called a suspension.
When the liquid drug is delivered into the dispersion medium, the
system form is called emulsion.

2. Classification of biphasic liquid dosage forms:
The biphasic liquid dosage forms have two types, emulsion and suspension.
Emulsion dosage form: It is a thermodynamically unstable system consisting of two
immiscible liquid phases, one of which is dispersed as globules within the other and
stabilized by an emulsifying agent. It has two types, water in oil type (w/o), and oil in a
water type (o/w). Examples-application, liniment, and lotion, etc.
Suspension dosage form: It is a biphasic liquid or semi-solid dosage form, in which
insoluble solid particles of the drug are homogeneously dispersed in a liquid or semi-
solid medium. Examples- Gels, lotion, aerosols, inhalation, and eye drop, etc.

3. Disadvantages of biphasic liquid dosage forms:
Not all drugs are compatible to formulate with biphasic form.
It is bulky and therefore difficult to handle, transport and store.
It is costly compared with the solid dosage form.

4. Advantages of biphasic liquid dosage forms:
It is used for the drugs that are insoluble in solution; therefore it is necessary to
prepare an insoluble form of the drug, which is then administered as a
suspension.
It exhibits higher bioavailability rates than other dosage forms.
Suspension can offer prolonged action of the drug since solid particles must be
dissolved before absorption.
Two incompatible ingredients/drugs can be included in a dose, one in each phase
of the emulsion.

5. Difference between monophasic and biphasic liquid dosage form:
• Liquid oral doses comprise a wide range of dosage forms, broadly
classified as the monophasic and biphasic liquid dosage forms.
• The major difference between monophasic and biphasic liquid
dosage forms is that the
• monophasic liquid dosage forms have a single homogeneous
phase,
• whereas biphasic liquid dosage forms consist of two distinct
phases.
• Both forms include at least one drug in formulation,
• monophasic forms are homogeneous and completely dissolve in
liquid,
• whereas biphasic forms are not dissolved in a vehicle.

6. • The HLB (Hydrophilic–lipophilic balance) Scale ranges 1-20
• Surfactants with higher HLB numbers (greater than 10) are more
hydrophilic
• Surfactants with lower HLB number (less than 10) are more hydrophobic
Higher HLB Scale valued surfactants are more hydrophilic and thus are more
water soluble. Similarly, lower HLB Scale valued surfactants are more lipophilic
and thus more oil soluble. So, higher HLB surfactants will created oil-in-water
emulsions and lower HLB surfactants will create water-in-oil emulsions:

22. methods commonly used to
prepare emulsions
Trituration Method
This method consists of
Dry gum method
and
Wet gum method.

28. Figure 1: Flocculation
Flocculation is the formation of clumps by the aggregation of fine particles in a
suspension. These clumps are called flocs or flakes. Flocculation may occur
spontaneously or due to the addition of a clarifying agent. However, this floc
formation is different from precipitation. It is because, in precipitation, dissolved
components form a solid while in flocculation, dissolved components form a solid.