PHARMACEUTICAL SUSPENSIONS AND EMULSIONS

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PHARMACEUTICAL SUSPENSIONS AND EMULSIONS
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Coarse Dispersions
(Lyophobic colloids)

• Suspension Solid drug in liquid vehicle

• Emulsion Liquid drug in liquid vehicle

• Oil-in-water emulsions (o/w)
• Water-in-oil (w/o)

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Reasons for Use

• Drug is insoluble
• Drug is more stable in suspension or emulsion
• There is a need to control the rate of release of
  the drug
• Drug has bad taste (oral)

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Routes of Administration

• Oral
• Ocular
• Otic
• Rectal
• Parenteral
• Topical

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I. Formulation of Suspensions
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Wetting
Wetting agent
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Well Formulated Suspension

• Resuspend easily upon shaking
• Settle rapidly after shaking
• Homogeneous mix of drug
• Physically and chemically stable during its shelf
  life
• Sterile (parenteral, ocular)
• Gets into syringe (parenteral, ocular)

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External Forces Acting on Particles
Gravity
Brownian Movement
V(?-?o)g

• Sedimentation equilibrium Gravity is neutralized
  by Brownian movement

2-5 ??m
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Settling and Aggregation
flock

• The suspension shall form loose networks of
  flocks that settle rapidly, do not form cakes and
  are easy to resuspend.
• Settling and aggregation may result in formation
  of cakes (suspension) that is difficult to
  resuspend or phase separation (emulsion)

cake
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Sediment Volume
Fvolume of sediment Vu/original volume Vo

• Vu

• Vo

• Vo

• Vu

F0.5
F1.0
F1.5
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DLVO Optimal Distance
Energy
No flocks can form
Repulsion
Attraction
Attraction
Distance
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Controlled Flocculation

• Flocculating agent changes zeta-potential of the
  particles (it can be electrolyte, charged
  surfactant or charged polymer adsorbing on a
  surface).
• If the absolute value of the zeta-potential is
  too high the system deflocculates because of
  increased repulsion and the dispersion cakes.

Non-caking
Caking
Caking
FVu/Vo
Flocculating Agent
-

-

Zeta-potential
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