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What are the two-phases of a suspension system?
- 1) Finely divided drug particles (suspensoid, dispersed phase)
- 2) Vehicle (dispersing medium
What are the advantages of suspensions
- Chemical Stability
- Liquid preparation
Liquid preparation allows for?
- Ease of swallowing
- Flexible administration
- Range of doses
Arrange Capsule, Coated tablet, Compressed tablet, Solution, Suspension from most bioavailable to least
Solution > Suspension > Capsule > Compressed Tablet > Coated Tablet
Oral suspensions are composed of?
- Viscous Vehicle
What are topical suspensions and how are they used?
- Applied to the skin
- Sometimes in the form of lotions
- Used as Ophthalmic, otic, nasal, or rectals
Can parenterals be considered parenterals?
Yes, parenterals can be suspensions
Two ways that commerical preparations are available?
What are ready to use suspensions like?
- May or may not contain stablilzers or additives
- Oral suspension
What are dry powders?
- For oral suspension
- Drug, suspending agent, disbursing agent are to be diluted and agitate with vehicle (usually purified water)
- These powders are reconstituted at the time of dispensing
- Unstable for extended time in aqueous vehicle like many antibiotics
What are some features of suspensions?
- Therapeutic efficacy
- Chemical stability
- Esthetic appeal
What is Thixotropy?
- Thicken while standing (stablizes the suspension)
- ThinnerLiquid when shaken (ease of pouring and application)
- Desirable for increasing phuysical stability of suspensions
What are the components of a suspension?
- Dispersed phase (Insoluble particles)
- Dispersion medium (additives, flavoring/odorant, sweetener, preservatives)
- *the order of mixing is important to the stability
What is Stoke's law take into consideration?
- Spherical particles
- Settle without turbulence or colliding with other particles in the suspensoid
- Without chemical or physical attraction for the dispersion medium
What is Stokes law?
- dx/dt =(d2 (p1 - pe)g)/18n
- dx/dt= rate of settling (sedimentation, velocity of fall)
- d= diameter of particles
- pi= density of the particle
- pe= density of the medium
- n= viscosity of the medium
- g= gravitational constant
What does Stoke's law describe?
What are the effects of particle size?
Small size=slower sedimentation rate
What are the effects of the density of a particle?
- Higher density=faster sedimentation rate
- Too small or low density then particles float and are difficult to distrubute
What are the effects of viscosity?
- Increase in viscosity=slower sedimentation rate
- High viscosity may cause problem pouring
How is the size reduced or particles?
- Dry milling
- Fluid energy grinding (jet milling, micronizing)
- Spray drying
What is micropulverization?
- Rapid, convenient, inexpensive
- Produces particles 10 to 50 micrometers
- Used for oral and topical suspensions
What is fluid energy grinding used for?
- aka jet milling, micronization
- Less than 10 micrometers
- Used for parenterals or ophthalmics
What size of particle is desirable for a particle in the dispersed phase?
1 to 50 micrometers
How does particle size affect the physical stability of the suspension?
- Alter the dispersed phase
- Small particle size (reduces sedimentation rate, uniform)
- Particles that are too small may cake on the bottom
What is caking?
- Small particles tick to bottom
- Resist breaking up when shaken
- Form aggregates of particles that are less suspendable in the suspending medium
How does the shape of particles affect caking?
- Symmetrical barrel shaped particles are more stable than asymmetrical needle shaped particles
- Needles cake upon standing that can not be redistributed
How can caking be avoided?
What are floculating agents?
- Clays (bentonite magma)
- pH of the dispersed phase (parenterals)
What are floccules?
- Loose aggregates of particles held together by weak particle-particle bonds
- Particles form a lattice that resists complete settling
- Settle faster than fine particles
- Less prone to compaction/caking
- Break up easily and distribute readily with agitation
How is the suspensoid supported
- Density of suspensoid
- Flocculation of suspensoid
- Amount of material needing support
What is rheology?
the study of flow
What is viscosity
- Maintain drug in suspension
- Enhancing stability
- Altering release rate
What are some thickening/suspending agents that help to suspend the suspensoid and provide structure?
- Microcrystalline cellulose
- Polyvinyl pyrrolidone
- Xanthum gum
What are some additives for suspensions
What is the Pennkinetic system?
- Drugs complexed with ion exchange resins
- Drug-resin complex particles coated with ethyl cellulose
- n the suspensions: Coated particls, drug remains adsorbed onto the resin but is slowly released by ion exchange process in the GI tract
What is an example of Pennkinetic system?
Tussionex Pennkinetic Extended-Release Suspension
How does the pennkinetic system work?
- Uses an ion-exchange polymer matrix system to control release of both hydrocodone and chlorpheniramine
- 1) Hydrocodone and chlorpheniramine are each bound to a polymer matrix. They hydrocodone particles are surrounded by a semipermeable coating.
- 2) Endogenous ions displace the active molecules from their polymer matrix.
- 3) Hydrocodone diffuses through the coating, extending its release
Why create a suspension?
- Patients not able to swallow solid dosage forms
- Compound suspensions from available solid dosage forms
How can we know information of stability of drugs in suspension?
- Faster decomposition rates
- Affects of pH
- Package insert
- Professional Literature
- Contact manufacture of the solid dosage form
Describe the extemporaneous prepeartion of Theophylline
- A 5mg/mL oral suspension may be made with tablets
- Crush one 300 mg extended release tablet in a mortar and reduce to a fine powder
- Add small portions of a 1:1 mixture of Ora-Sweet and Ora-Plus and mix to a uniform paste
- Mix while adding the vehicle in equal proportions to almost 60 mL
- Stable for 90 days at room temperature
How is the dispersed phase obtained?
Uiform small particles of drug after particle size reduction
How is wetting done and what does it do?
- Displace air in the crevice of the particles to allow the penetration of dispersion medium into the powder
- Slowly adding wetting agent
- Use a minimal amount of wetting agents
- Form a paste
How do you add the dispersion medium?
- Add the vehicle to the paste by parts with constant stirring
- Portion of vehicle is used to wash suspensoid from mixing equipment
- Vehicle used to qs final volume
- final product passed through colloid mill, blender, mixing device for uniformity
What are additives to suspensions?
- Flavors and colors
- Preservatives (preserve against bacterial and mold contamination)
What should formulations for neonates not include?
Flavoring is not needed for neonates because?
Taste in underdeveloped in neonates?
Benzyl alcohol (a preservative) leads to what is neonates?
Gasping syndrome--multiple organ dysfunction and death
Propylene glycol (a preservative) should not be used in neonates because?
It creates seizures or stupor
Alcohol is not used in suspensions for neonates because?
- Alters liver function
- Gastric irritation
- CNS depression
- Aromatic Elixir NF contians 21-23% alcohol
How should suspensions be packaged?
- Wide mouth container (easy, even pouring)
- Air tight, ligh resistant container
- Adequate space inside container (for through mixing)
How should suspensions be stored?
- Protected from freezing
- Protected from excessive heat
- Store at room temperature or refrigerated *Depending on the characteristic of the drug
How should suspensions be labeled?
- Internal vs external use
- Beyond use date
- Shake well prior to use
- (Use the correct meauring tool, watch for color changes or changes in consistency)
Definition of suspensions
- Two phase system
What are suspensions composed of?
- Dispersed phase
- Dispersing phase (dispersion medium)
How are suspensions classified?
- Coarse dispersions
- Fine and colloidal dispersions
What are the applications of suspensions
- Drug stability
- Liquid therapy
- Flexibility of dosage forms
- Liquid forms from dry powders for reconstitution
- Particle size
- Fluid-energy grinding
- Particle shape
- Formation of flocs/floccules/flakes
What are some common suspension vehicles?
- 0.5-5% methylcellulose dispersion
- 0.5-1.5% sodium carboxymethylcellulose dispersion
How are suspensions prepared?
- Particle size reduction, solid ingredients
- Wetting of powder (wetting agents-glycerin, alcohol, surfactant), thick paste
- Vehicle added with constant stirring (colorants, flavorings, preservatives)
- Blending of mixture for uniformity
What are extended-release suspensions?
- Combination of drug with an ion exchange resin
- Preparation of coated particles
- Impregnation of drug in wax matrix
Beyond use date of a water containing suspension?
14 days if refrigerated
What is a lotion?
- Thick liquid suspension or emulsion for topical application to the skin.
- Fluidity permits rapid and uniform application over a wide surface area
- Lotions dry on the skin soon after application, leaving a thin coat of medicinal componetnts on the skin surface
- Lubricating effect: applied to intertrigious areas (areas where the skin rubs together, such as between teh fingers, between the thighs, under the arms, etc)
What types of vehicles are used in lotions?
Vehicles that have large aqueous content
Lotions may be prepared in the same manner as?
Suspension, emulsions or solutions
What are some examples of lotions?
- Calamine lotion
- Hydrocortisone lotion
How can lotions be prepared?
From creams (o/w emulsions) by diluting with water or aromatic water; add slowly w/ continuous stirring, short expiration date