Lecture 2 - Powder Dose Forms Flashcards
Describe the physical properties of a powder
Most pharmaceutical substances occur in solid state
- May be amorphous or crystalline
- Term powder may refer to physical state or finished product
Explain how particle size is a key attribute in pharmaceutics & how particle size is relevant to dissolution, stability, suspendibility etc.
*smaller size, faster it can work/get to action site
Particle size/shape Influences factors such as:
- Dissolution rate, suspendability, uniformity, grittiness
- Small particle size associated with:
- Larger surface area, faster dissolution, better suspendability
- Particles of similar shape and size tend to blend more uniformly for more homogeneous mixtures
- Homogeneity very important for many dose forms (smaller size/shape is key for achieving homogeneity)
*for ointments/creams, it’ll be the particle size that makes it grainy/rough
Identify the different methods of measuring particle size & explain how particle size impacts on apparent density
Size may be determined by:
- Sieving methods - size of mesh on a sieve will determine what can go through it
- Microscopy
- Sedimentation rate - will sediment at diff. levels
- Light scattering
Particle shape seen by microscopy or inferred through angle of repose 6
d = m/v so density we need the mass
Identify methods of reducing particle size
- Comminution: process of reducing particle size of a solid
- methods: trituration with a mortar & pestle (porcelain material preferred b/c has rougher SA (better for breaking down particles) - Levigation:
- with spatula; use compatible levigating agent & prepare solid for incorporation into a semi-solid vehicle
- small particle size makes product smooth
- with mortar & pestle: useful for preparing suspensions (start with levigating agent)
- small particle size to aid in dispersion & suspension
- mills are used in industry
Identify techniques used for blending powders
When powders are to be combined into a homogeneous mixture important all the particles are about the same size
- Powders with different particle size stratify or segregate and do not remain homogeneous
- Trituration may SIMULTANEOUSLY reduce and make size uniform (beneficial)
Identify techniques for issues with eutectics (into liq. form)
2 strategies:
1. Allow eutectic to form while triturating
- Add an adsorbing inert material until mix is powder- like
- Use Ca or Mg carbonate or oxide, talc
- Mix the components separately with adsorbent
- Combine the protected materials
- Add remaining materials using geometric dilution
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Mediated Powders
Powder is a drug or mixture in the solid state
- May be only drug or drug mixed with excipient
- Exist as fine uniform particles in homogeneous mixture excipients
May be designed for EXternal use (dusting powder, powder for dissolution followed by soaking or application)
May be designed for INternal use (May be incorporated into tablets, capsules or powder papers, may also be in bulk for internal use (Metamucil)
Variety of containers are available for topical powders depending on the application
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Medicated Powders (solid state offers some advantages)
- Increased stability - Most drugs more stable in solid state
- Flexible - Dose forms such as tablet allows controlled release (i.e. tablet releases drug gradually (12-24 hrs), patient can use 1-2x a day & get effect)
& Each dose form can contain different amounts of drug - Convenient - Solid forms usually easily administered & Easy to package and ship
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Bulk powders….Oral
Non-potent (i.e. room for errors is okay) medications which can be dosed with acceptable accuracy using teaspoons or tablespoons
- Orally administered powders usually dietary supplements, antacids, laxatives
- Usually mixed into juice or water prior to oral administration (some are specific to what it can be mixed with)
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Bulk powders…External
Bulk powders for external use dusted onto skin using a sift-top container
- Often contain an active such as a topical fungicide and a diluent or vehicle powder
- Diluents should be inert, free of grittiness protects skin and absorbs secretions eg bentonite, talc, kaolin
- Must have ‘For external use’ auxiliary label
ex: fungal infection on foot
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Bulk powders…External
Bulk powder for topical use (fine & microfized powders; therefore won’t feel anything)
- some you just breath in forcefully or press to activate
ex: Micatin (Miconazole) and Tinactin (Tolnaftate)
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Bulk powders…Internal
Bulk powder for oral use
ex: Metamucil (Psyllium) powder
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Powders…Metered for inhalation
Some powders intended for insufflation into body cavities
- These are now packaged in aerosol containers under pressure
Some are designed to deliver medication directly to the lung
ex: Aerolizer, Handihaler, Flexhandler, Diskus, Twisthaler
- With these devices, the patient inhales the medication in the form of a fine powder rather than an aerosol.
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Divided powders
- Extemporaneous dose form useful for medications for young children or the elderly (difficulty swallowing)
- Single dose of powdered medication wrapped in paper or foil-plastic laminates
- Delivers an accurate quantity of medication and can be used for potent drugs
- Powder consists of active drug uniformly distributed in a soluble diluent like lactose
- Contents of paper dissolved in water or juice just prior to administration
- Useful when medication only available as solid oral dose form and patient cannot take
Classify different types of powder dose forms & identify advantages & disadvantages as well as limitations
Granulations…
Coarse particles made by blending powders the moistening to form a pasty mass
- Mass passed through sieve and formed granules are allowed to air-dry
Used in preparation of tablets and sometimes capsules
- Can also be used for non-potent drugs as a bulk
preparation where teaspoon or tablespoon used to measure and
product dissolved/dispersed in water or juice
Effervescent granules can be made by mixing granules made with citric and tartaric acids (1:2) with granules made with sodium bicarbonate.
- More common to see pressed into an effervescent tablet like Alka-Seltzer (like aspirin used for headaches)
