Dosage Forms II

• Parenteral Route — Dosage Forms


  Injections are usually sterile solutions or suspensions of drugs in a suitable aqueous or non aqueous vehicle and are usually classified according to route of administration
• Small-volume parenterals (up to 100ml)


  • Single-dose ampoules
  • Multiple dose vials
  • Pre-filled syringes
• Single-dose ampoules

  • Plastic or glass ampoules, but for glass ampoules, glass particles can fall into the injection during opening
  • Single use only and no chemical antimicrobial preservatives as once they're open, they're used straight away
  • Sterilisation, so at the manufacturing point, there is no bacteria or microbes in this preparation
• Multiple dose vials


  • Composed of thick walled glass container that is sealed with a rubber closure
  • Contents can be removed in portions by needle e.g. insulin, which is delivered subcutaneously
  • Fragments of the closure may be released into the product when the needle is inserted through the closure
  • Repeated withdrawal of injection solution increases risk of contamination of the product and therefore these products must have antimicrobial preservative to inhibit microbial growth
  • Contents can be in either liquid or powder form
• Pre-filled syringes


  • Available for immediate use
  • Expensive
  • Quite common for vaccines
• Large volume parenterals (>100ml)


  • Packaged in glass bottles, semi-rigid or collapsible plastic containers
  • All large volume parenteral products must be sterilized after filling into their final containers
• Large volume parenteral products


  • Infusions
  • Irrigation solutions
  • Injections
• Injections — Vehicles and Additives


  • Non toxic
  • Inert — doesn't interact with the main ingredients
  • Water for injection — used for small volume parenterals
  • Water-miscible co-solvents (glycerine and propylene glycol)
  • Fixed vegetable oils (e.g. corn oil, sesame oil ) — intramuscular
  • Antimicrobials, antioxidants (ensures parenteral remains stable), buffers (allows a suitable pH to be maintained, so when it's injected into the blood, it'll have a similar pH as the blood and resist changes in pH, chelating agents and tonicity-adjusters
• Implants


  • Solid dosage forms which are inserted under the skin
  • Sterile and placed under the skin via a minor procedure
  • Commonly used for hormone replacement therapy or as a contraceptive
  • Release of the drug from implants is slow and long term therapy is achieved
• Implant example


  • Norplant, which can be used as a contraceptive implant, has an effect that continues for up to 3 years
• Topical Route — Dosage Forms

  • Creams — semi-solid emulsions for external use only. Medicaments are dissolved or suspended in creams
  • Ointments — semi solid preparations consisting of one or more medicaments dissolved or dispersed in a suitable base
  • Gels — usually transparent, non greasy, semi-solid preparations mainly used externally
  • Lotions — Liquids for external use only. Solutions, suspensions or emulsions
  • Paints — A liquid preparation intended for application to skin or mucous membranes to soothe the skin
  • Pastes — Semi-solids for external use. Contain high proportion of powdered ingredients
  • Collodions — a liquid preparation for external use. Liquid is painted on the affected skin, where it forms a flexible film
  • Dusting Powders — a preparation consisting of one or more substances in finepowder for external use
  • Liniment — liquids for external use. Used to alleviate discomfort of muscle strains and injuries
• Aqueous creams


  • Oil in water emulsion as bases. Produced using synthetic waxes e.g. cetomacrogol
  • They are the best bases to use for rapid absorption and penetration of drugs
  • They are thin, white and smooth in consistency
  • Can be easily removed as external phase is water, so can be washed off
• Oily creams


  • Water in oil emulsions as bases. Produced by emulsifying agents of natural origin e.g. beeswax
  • These bases have good emollient properties
  • They are creamy, white or translucent and rather stiff, due to the high oil content, compared to aqueous creams
  • Contains water so susceptible to microbial contamination and either have a preservative to inhibit microbial growth or given a short shelf life
• Transdermal Delivery Systems


  • Transdermal (bypasses first layer of the skin and go through the derma of the skin) patches
  • Adhesive patches, applied to skin
  • Continuous drug release over a period of time from a few hours to 7 days
  • Drug is absorbed through the skin into the systemic circulation
• Transdermal patch examples


  • Estradiol for menopausal symptoms and prevention of osteoporosis
  • Nicotine patches are used for either 16 or 24 hour periods and are available in range of strengths
• Gargles


  • Aqueous solutions used to treat infections of the throat
  • May contain antiseptics, analgesics or weak astringents to with the relief of throat infections
  • Sometimes in concentrated form so may need diluting by patient before use
  • Not to be swallowed — if they do, advise to see their GP as it can be harmful
• Mouthwashes

  • Used for oral hygiene and treat infections of the mouth
  • Sometimes in concentrated form so may need diluting by patient
  • Not to be swallowed
• Time of Onset of Action for Different Dosage Forms

  • Seconds — IV injections
  • Minutes — IM and SC injections, buccal tablets, aerosols
  • Minutes to hours — Short term depot injections, solutions, powders, granules, caps, suspensions, tablets, modified release tablets
  • Several hours — Enteric coated formulations
  • Days — Depot injections, implants
  • Varies — Topical preparations