liquid 1

• Dispersion


  A heterogeneous system consisting of a dispersed phase being distributed throughout a dispersion medium
• Dispersed liquid dosage forms

  • Suspensions
  • Emulsions
• Dispersed phase


  Internal phase/discontinuous phase
• Dispersion medium


  Dispersing phase/external phase/continuous phase
• Coarse dispersion


  Coarse, visible under the microscope (10-50 µm)
• Fine dispersion


  Fine, visible under the electron microscope
• Types of fine dispersion

  • Colloidal dispersion
  • Molecular dispersion
• Suspensions


  Preparation containing finely divided particles (suspensoids) distributed throughout a vehicle which is the drug exhibit maximum solubility
• Rationale for formulating suspensions

  • Drugs exhibit minimum solubility
  • Drugs unstable in solution
  • Preference for liquid form
  • Taste masking
• Ideal suspensions


  • Should settle slowly and should be readily redispersed on gentle shaking of the container
  • The particle size of the suspension remains fairly constant throughout its long period of undistributed standing
  • The suspensions should pour readily and evenly from its container
  • It should be free from large particles which spoil its appearance, give a gritty taste to oral preparations, and also cause irritation to sensitive tissues when applied externally
• Types of suspensions based on application

  • Oral suspensions
  • Topical suspensions
  • Parenteral suspensions
  • Ophthalmic suspensions
• Types of suspensions based on concentration and particle size

  • Saturated suspensions
  • Dilute suspensions
  • Coarse suspensions
  • Colloidal suspensions
• Types of suspensions based on the nature of solutes

  • Flocculated suspensions
  • Deflocculated suspensions
• Types of suspensions based on commercial availability

  • Ready-to-use suspensions
  • Dry powder for suspensions
• Subtypes of suspensions


  • Gels
  • Magmas/milk
  • Lotions
  • Mixtures
• Reconstitution of dry powders for oral suspensions

  1. Preparation: drug product, purified water, measuring device

  2. Read the direction for the constitution. Lightly tap the bottle

  3. Add half of the needed diluent. Shake the slurry until all the powder has been suspended. Allow to stand

  4. Add the remaining amount of solvent. Shake
• Administration of suspensions


  • Oral suspensions
  • Topical suspensions
  • Parenteral suspensions
  • Ophthalmic suspensions
  • Rectal suspensions
• Flocculated suspensions


  Redispersable (agitation), suspension is not pleasing in appearance, particles form loose aggregates and form a network-like structure, repulsion energy is low, attraction energy is high
• Deflocculated suspensions


  Non-redispersable (agitation), suspension is pleasing in appearance, particles exist as separate entities, repulsion energy is high, attraction energy is low
• Differences between flocculated and deflocculated suspensions

  • Floccules
  • Nature of particles
  • Repulsion Energy
  • Attraction Energy
  • Rate of Sedimentation
  • Porosity of Sedimentation
  • Caking
  • Appearance of Supernatant liquid
  • Redispersion
• Gels


  Semisolid system, consisting of dispersion made up of either small inorganic particles or large organic particles which are enclosed and interpenetrated by a liquids
• Phenomena in gels


  • Thixotropy
  • Imbibition
  • Swelling
  • Syneresis
  • Xerogel
• Lotions


  Liquids suspensions intended for external application to the body
• Lotions


  • Calamine lotion
  • Calamine + Diphenhydramine HCl Lotion (Caladryl)
• Magmas


  Aqueous suspensions of insoluble inorganic drugs differ from gels mainly in that the suspended particles are larger
• Preparation of magmas


  Hydration, Chemical Reaction: MgSO4 + NaOH → Mg(OH)2
• Magmas


  • Milk of Magnesia
  • Bentonite magma
• Mixtures


  Oral liquids containing 1 or more API dissolved, suspended, and dispersed in a suitable solvent
• Mixtures


  • Bismuth subsalicylate (Kaopectate®)
  • Bordeaux Mixture
• Formulation considerations for suspensions

  • Wettability
  • Particle Interaction and Behavior
  • Sedimentation Rate
  • Drug Substance
  • Solvents
  • Organoleptic Agents
• Wettability


  Solids can either be solvent-loving or solvent-hating, can be increased by addition of surfactant, hydrophilic polymers, or water-insoluble hydrophilic materials
• Particle Interaction and Behavior

  Sensitivity to electrolytes, lyophobic materials are sensitive to addition of salts, lyophilic material may experience salting-out effects with large amounts of electrolytes
• Sedimentation Rate


  Factors influencing: velocity, density of the drug
• Drug Substance


  Should be finely divided, insoluble solids
• Solvents used as continuous medium

  • Water
  • Alcohol
  • Glycerin
  • Polyethylene glycol
  • Polypropylene glycol
• Organoleptic Agents


  Flavorants, Colorants, Sweeteners
• Considerations in Suspension Formulation

  • Wettability
  • Particle Interaction and Behavior
  • Sedimentation Rate
  • Drug Substance
  • Solvents
  • Organoleptic Agents
  • Suspending Agents
  • Wetting Agents
  • Flocculating Agents
  • Buffering Agents
  • Defoamer
  • Stabilizers
  • Humectants
• Wettability


  Solids can either be solvent-loving or solvent-hating. Increase wettability by the addition of: 1) Surfactant, 2) Hydrophilic polymers (sodium CMC), 3) Water-insoluble hydrophilic materials (bentonite, aluminum-magnesium trisilicates, and colloidal silica)
• Particle Interaction and Behavior

  Sensitivity to electrolytes: lyophobic materials in suspension are sensitive to the addition of salts, lyophilic material is readily wet by water but large amounts of electrolytes may cause salting-out effects
• Sedimentation Rate


  Delay or slow rate of settling. Factors Influencing Sedimentation Rate: Velocity, Density of the drug