PS 2 B

• pharmaceutical powders


  drugs generally come as powders but are often turned into a different dosage form. mixtures of finely divided drugs or chemicals in a dry form intended for external or internal use. manufactured stepwise mixing and blending of ingredients, may then be granulated. can be administered dry, in suspension or dissolved. bulk powder (a bulk where a quantity is taken with a scoop) or divided powder (sachets) . can be fine, coarse or granules
• use of powders

  dusting powders for skin disorders and wounds (nappy rash), insufflation (introducing a powder into a body cavity, powder inhalers for asthma), dentifrices (paste or powder for cleaning the teeth and or false teeth), douches (for preparation of cleansing solutions for vagina and enemas)
• examples of dusting powders

  chlorhexidine dusting powder (disinfectant), and zinc, starch and talc dusting powder (absorbent for nappy rash)
• advantages of dusting powders

  solid preparations are more stable than liquid preparations (dry and protected from air). powders and granules are pleasant, easy and convenient ways to administer small or large doses. can be applied without touching the skin or wound. normally do not contain preservatives (don't need them) and don't irritate skin, absorb skin moisture and reduce friction
• disadvantages of dusting powders


  may block pores causing skin irritation, easily contaminated, not suitable for dispensing hygroscopic (a drug that tends to absorb water from the air and forms crystals consequently destabilising) or deliquescent drugs (a substance that absorbs water from the air and becomes liquid / dissolves), may be inhaled by accident - breathing difficulties, not suitable for application to broken skin (can clog up a wound and dry it), easily rubbed off, low drug absorption.
• internal powders

  administered as dry powders: aerosol powders (dry powder inhalers) and oral divided powders (for swallowing not inhaling for people who can't take tablets/capsules). administered after dissolution/suspension in water: effervescent and non-effervescent antacids, antibiotics syrups/suspensions, laxatives and powders for reconstitution for injection
• internal pharmaceutical powder examples

  compound magnesium trisilicate oral powder (antacid for indigestion and heartburn) codeine phosphate divided powder (oral analgesic)
• advantages of oral powders

  solid preparations are more stable than liquid preparations, powders and granules are pleasant, easy and convenient ways to administer small or large doses, disperse and dissolve faster in the stomach and are absorbed more quickly than tablets and capsules
• disadvantages of oral powders

  bulky and less convenient to carry than tablets and capsules, may be difficult to mask unpleasant taste, not suitable for low dose potent drugs, not suitable for drugs that are degraded in stomach acid, not suitable for dispensing hygroscopic or deliquescent drugs
• packaging of powders

  brown glass jar + scoop, sachets, powder shaker, bottle/vial for making a solution
• micromeritics

  the science of small particles. particles can come in different sizes and distributions. particle size is significant in formulation, manufacture and use of products (especially capsules and tablets). particle size parameters (mean diameter, median, mode and spread), determined using microscopy and counting particles along a line. serving powder through series of sieves to determine percentages retained in each size group, sedimentation: size determination based on fact that particles sediment at rates proportional to their size squared.
• mass volume and density relation

  p = m/v
• density and porosity of powders

  true density, bulk denisty, tapped density and porosity
• true density

  the density of the solid phase (excluding all void space between and inside particles) mass/vol (true).
• bulk density


  the density of a powder including void space, after sieving but before tapping. =mass / vol(bulk)
• tapped density

  density of a sieved powder after multiple tapping to consolidate particles and minimise void space
• porosity

  percentage of void space in a powder = (volbulk - voltrue) / volbulk x100%
• flow properties

  sucessful manufacture of drug products relies on efficient, smooth and predictable flow of powders involved. rate and extent of flow depends on forces applied (gravity), particle size and density, adhesion and cohesion, electrostatic forces (charge, attraction and repulsion), surface smoothness/roughness (mechanical interlocking and friction)
• Carr's compressibility index and flowability

  tapped density - bulk density / tapped density x 100%. small percent the better the flowability
• flowability

  how well a powder flows: angle of repose, pour powder onto disc and form a mountain and then measure the handle of the mountain formed. the smaller the angle the better the flowability. less than 31 is excellent, 32-45 is good, 46-56 is medium 57+ is poor
• hard gelatin capsules

  contain powder or beads/granules. gelatin derived from animal skin and bones or synthetics. rounded hemispherical shape with a cap that locks into the body (which has the volume of the capsule). have airvents to allow air to escape when filling. sizes 000 to 5 trade offs with size for swallowing and handling
• excipients in hard gelatin capsules

  diluent/filler (lactose) , binder/disintegrant (starch), lubricant (silica) , granulation liquid (ethanol and/or water) and colourant in shell
• manufacture of hard gelatin capsules

  complex and slower than tablet, more expensive. contents blended and granulated (not compressed), sufficient diluent added to make volume, capsule bodies filled and contents lightly compressed (if needed), capsules capped and sealed. content may be a viscous non-aqueous liquid that later solidifies or in pellets for easier encapsulation
• calculating capsule filling

  capsules measured in mL, calculate the volume of a drug from w/p (tapped) and then fill the rest of the volume with excipient
• capsule filling

  punch method, capsule body is punched down into a pile of the powder product, cap is placed on. funnel method - capsule is open and a funnel is place ontop and capsule is filled and compressed and cap is added. capsules can also be filled on a tray
• hard gelatin capsules advantages

  allow for flexibility in content, formulation and shell colours. contents may be powder, granules, beads, small tablets, semisolids or ground herbs. accurate, reproducible dosing. can be modified release. slippery when moist, easy to swallow. shell disguises taste of capsule contents. capsule shell dissolves quickly in stomach yielding rapid drug release. can be blinded for clinical trials
• disadvantages of hard capsules

  limited number of shell suppliers. slower and more expensive than a tablet. not suitable for highly soluble drugs, rapid release may cause localised irritation in stomach lining. not divisible, limiting dosage adjustment. not suitable for hygroscopic/deliquescent drugs that absorb moisture from the shell making it brittle, large sizes choking problems and small are hard to handle. not suitable for young children, shells can get sticky in high humidity and brittle in low
• soft gelatin capsules

  shell - gelatin plasticised with glycerin sorbitol or low MW PEG (polyethylene glycol). drug homogeneously dispersed as a viscous solution or suspension in vegetable oil or low MW PEG. capsule shells manufactured, filled and hermetically sealed in a single operation
• soft gelatin capsule excipients

  diluents (lactose), binder/disintegrant (starch), lubricant (talc), solvent (water-immiscible vegetable oil or water-miscible low MW PEG)
• manufacture of soft gel capsules

  the shell is made into a rib and the drug + excipients are punched into the shell and rolled into shape.
• packaging of capsules

  bottles and blisters
• soft gelatin capsules advantages


  drug homogeneously dispersed in oily or PEG solution or suspension. rapid release of the drug in stomach. drug more stable than in bottled or oral solution. content uniformity usually better than hard gelatin capsules and compressed tablets. can be used for oils and oily mixtures. good mouth feel. may be formulated to be chewable. may be formulated for rectal administration.
• soft gelatin capsules disadvantages

  special manufacturing methodology required. more expensive to manufacture than conventional capsules and tablets. potential adverse interaction between drug and capsule shell. can get damp and sticky if exposed to humidity. large capsules can get stuck in throat
• capsule digestion

  dissolution of capsule shell, release of capsule contents, fine particles in suspension, some/all drug dissolved in gastric chyme (some acid/enzymatic degradation) transfer to duodenum and small intestine. absorption through gut wall (enzymatic metabolism) transfer to liver via portal vein (hepatic first pass metabolism) then elimination or systemic circulation and elimination