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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
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What are the advantages of suspensions
- Chemical Stability
- Liquid preparation
- Bioavailability
- Taste
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Liquid preparation allows for?
- Ease of swallowing
- Flexible administration
- Range of doses
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Arrange Capsule, Coated tablet, Compressed tablet, Solution, Suspension from most bioavailable to least
Solution > Suspension > Capsule > Compressed Tablet > Coated Tablet
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Oral suspensions are composed of?
- Sweetened
- Flavored
- Viscous Vehicle
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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
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Can parenterals be considered parenterals?
Yes, parenterals can be suspensions
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Two ways that commerical preparations are available?
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What are ready to use suspensions like?
- May or may not contain stablilzers or additives
- Oral suspension
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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
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What are some features of suspensions?
- Therapeutic efficacy
- Chemical stability
- Esthetic appeal
- Resuspendability
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What is Thixotropy?
- Thicken while standing (stablizes the suspension)
- ThinnerLiquid when shaken (ease of pouring and application)
- Desirable for increasing phuysical stability of suspensions
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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
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What is Stoke's law take into consideration?
- Uniform
- Spherical particles
- Settle without turbulence or colliding with other particles in the suspensoid
- Without chemical or physical attraction for the dispersion medium
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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
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What does Stoke's law describe?
Sedimentation rate
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What are the effects of particle size?
Small size=slower sedimentation rate
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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
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What are the effects of viscosity?
- Increase in viscosity=slower sedimentation rate
- High viscosity may cause problem pouring
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How is the size reduced or particles?
- Comminution
- Dry milling
- Micropulverization
- Fluid energy grinding (jet milling, micronizing)
- Spray drying
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What is micropulverization?
- Rapid, convenient, inexpensive
- Produces particles 10 to 50 micrometers
- Used for oral and topical suspensions
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What is fluid energy grinding used for?
- aka jet milling, micronization
- Less than 10 micrometers
- Used for parenterals or ophthalmics
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What size of particle is desirable for a particle in the dispersed phase?
1 to 50 micrometers
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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
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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
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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
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How can caking be avoided?
Floccules
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What are floculating agents?
- Clays (bentonite magma)
- Electrolytes
- Surfactants
- pH of the dispersed phase (parenterals)
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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
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How is the suspensoid supported
- Density of suspensoid
- Flocculation of suspensoid
- Amount of material needing support
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What is rheology?
the study of flow
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What is viscosity
- Maintain drug in suspension
- Enhancing stability
- Altering release rate
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What are some thickening/suspending agents that help to suspend the suspensoid and provide structure?
- Carboxymethylcellulose
- Methylcellulose
- Microcrystalline cellulose
- Polyvinyl pyrrolidone
- Xanthum gum
- Bentonite
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What are some additives for suspensions
- Colors
- Flavors
- Preservatives
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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
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What is an example of Pennkinetic system?
Tussionex Pennkinetic Extended-Release Suspension
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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
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Why create a suspension?
- Patients not able to swallow solid dosage forms
- Compound suspensions from available solid dosage forms
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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
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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
- Lable
- Stable for 90 days at room temperature
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How is the dispersed phase obtained?
Uiform small particles of drug after particle size reduction
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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
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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
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What are additives to suspensions?
- Flavors and colors
- Preservatives (preserve against bacterial and mold contamination)
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What should formulations for neonates not include?
- Colorings
- Flavorings
- Breservatives
- Alcohol
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Flavoring is not needed for neonates because?
Taste in underdeveloped in neonates?
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Benzyl alcohol (a preservative) leads to what is neonates?
Gasping syndrome--multiple organ dysfunction and death
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Propylene glycol (a preservative) should not be used in neonates because?
It creates seizures or stupor
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Alcohol is not used in suspensions for neonates because?
- Alters liver function
- Gastric irritation
- CNS depression
- Aromatic Elixir NF contians 21-23% alcohol
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How should suspensions be packaged?
- Wide mouth container (easy, even pouring)
- Air tight, ligh resistant container
- Adequate space inside container (for through mixing)
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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
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How should suspensions be labeled?
- Internal vs external use
- Storage
- Beyond use date
- Shake well prior to use
- (Use the correct meauring tool, watch for color changes or changes in consistency)
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Definition of suspensions
- Two phase system
- Dispersion
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What are suspensions composed of?
- Dispersed phase
- Dispersing phase (dispersion medium)
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How are suspensions classified?
- Coarse dispersions
- Fine and colloidal dispersions
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What are the applications of suspensions
- Drug stability
- Liquid therapy
- Flexibility of dosage forms
- Liquid forms from dry powders for reconstitution
- Palatability
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Define suspensoid
- Particle size
- Comminution
- Micro[pulverization
- Fluid-energy grinding
- Particle shape
- Formation of flocs/floccules/flakes
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What are some common suspension vehicles?
- 0.5-5% methylcellulose dispersion
- 0.5-1.5% sodium carboxymethylcellulose dispersion
- Ora-Plus
- Suspendol-S
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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
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What are extended-release suspensions?
- Combination of drug with an ion exchange resin
- Preparation of coated particles
- Impregnation of drug in wax matrix
- Microencapsulation
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Beyond use date of a water containing suspension?
14 days if refrigerated
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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)
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What types of vehicles are used in lotions?
Vehicles that have large aqueous content
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Lotions may be prepared in the same manner as?
Suspension, emulsions or solutions
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What are some examples of lotions?
- Calamine lotion
- Hydrocortisone lotion
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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
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