Parenteral Administration Flashcards
What is parenteral administration?
sterile preparations for administration by injection, infusion or implantation into humans or animals
What is critical in parenteral administration?
- ensure sterility
- avoid contaminants
Why may parenteral administration be chosen?
- poor drug stability in GIT (inactivation, degradation)
- loacl administation
- quick onset of action (drug directly into systemic circ)
- delayed/prolonged release (implants, IM inj)
- if enteral route not available (unconcious, unable to swallow)
What are the main routes of parenteral administration?
- intramuscular - muscle under skin (90deg)
- intravenous - veins in dermis (25deg)
- subcutaneous - fatty tissue under dermis (45deg)
- intradermal - dermis (15deg)
Describe intravenous administartion.
- single dose
- <10mL
- emergency
- continuous infusion
- >500mL
- fluid replacement, nutrition (emulsions)
- into peripheral or central veins
- aqueous: solutions, emulsions, nanosuspensions
Why cant suspensions be administered via IV?
particles too big - could embolise in smaller capillaries
Where are peripheral and central veins located?
peripheral: forearm/elbow, back of hand
central: superior vena cava
When would the central vein by accessed for parenteral administration and what can be given?
- frequent access required
- limited peripheral access
- eg
- antibiotics (long term)
- parenteral nutrition
- chemo
- irritating solution
Why is parenteral nutrition given via peripheral veins?
- high osmolarity = diluted quicker as vein is bigger
What are advantages vs disadvantages of IV admin?
+
- 100% bioavailability
- rapid onset
- rapid dilution in blood circ
- useful if drug too irritating for SC or IM
- self admin possible
-
- invasive, inconvenient, restrictive
- strict sterility requirements
- aseptic required
- hard to reverse
- training required
- higher production cost
- risk of embolism = limit to type of formulation
- risk of extravasation (damage to veins)
- management of waste (sharps)
Describe subcutaneous administration.
- fatty tissue in:
- upper arm
- anterior thigh
- lower abdomen
- volume 1-2mL
- if larger - divided doses, infusion - slow rate (palliative/hydration)
- mixed with hyaluronidase (breaks down connective tissues)
- if larger - divided doses, infusion - slow rate (palliative/hydration)
- aqueous solutions/suspensions, oily solution/suspensions
- impact of formulation and liposolubility on diffusion rate and onset of action
Why is hyaluronidase added to large volume for SC admin?
breaks down connective tissues = allows admin of large volumes eg rituximab
What are advantages vs disadvantages of SC admin?
+
- more patient friendly than IV
- patients can be taught to self inject
- can be suspensions to control release
-
- invasive, inconvenient, restrictive
- response not always predictable
- impact of changes in blood supply, temp, site of inj
- some enzymatic activity eg peptidases
- strict sterility requirements
- aseptic required
- hard to reverse
- training required
- higher production cost
Describe intramuscular administration.
- skeletal muscle below SC tissues
- far from nerves, blood vessels
- upper arm (deltoid), thigh in younger, buttock in adults
- <4mL or up to 10mL in divided doses
- aqueous solutions/suspensions, oily solutions/suspensions/emulsions
- impact of formulation and liposolubility on diffusion rate and onset of action
What are advantages vs disadvantages of IM admin?
+
- more patient firnedly than IV
- rapid onset possible
- variety of formulations
- alternative to SC for irritant drugs
- possible controlled release
- better than SC for larger volumes
-
- invasive, inconvenient, restrictive
- impact of blood supply on absorption - affected by exercise
- strict sterility requirements
- aseptic required
- hard to reverse
- training required
- higher production cost
- management of waste (sharps)
What are formulation considerations for parenteral administration?
- sterility - bypasses barriers
- excipients - compatabile and non toxic
- containers - glass or plastic, ideally clear, should protect against contamination, tamper evident
- endotoxins - cause fever and shock
- particulates - free of visible particles
What is the limits for subvisible particles in parenteral administration?
- depends on ROA
- higher for SC or IM, IV stricter
- exemptions:
- radiopharmaceuticals
- products to be used with final filter
What excipients are added to solutions for parenteral formulation?
- co solvents
- ethanol
- glycerol
- propylene glycol
- solubilising agent
- surfactants
- cyclodextrins
- suitable oil
What excipients are added to emulsions for parenteral formulation?
- emulsifiers
- lethicin
- sorbitan fatty acid ester
- suitable oils
- arachis oil
- sesame oil
- soybean oil
What excipients are added to suspensions for parenteral formulation?
- for aq: suspending agents (increase viscocity)
- methylcellulose IM
- wetting agents (uniform suspension)
- surfactant eg polysorbate
- suitable oils
What is the acceptable range of pH for parenteral formulations?
3-9
otherwise too painful
How can you adjust tonicity of parenteral formulations?
- NaCl
- dextrose
What are the different categories of parenteral preparations?
- injections and infusions
- gels for injections
- implants
Summarise the use of injections and infusions in parenteral preparations.
- vials, prefilled syrings, infusion bags
- antimicrobial preservatives should not be used if single dose >15mL
- infusions are isotonic to blood, LVP are 100-1000mL no preservatives, sterile soluitons/ emulsions with no phase separation (cracking or creaming) eg diazemul
- injections are sterile, clear and particle free eg insulin, antibitoics
Summarise the use of gels for injections in parenteral preparations.
- sterile semi-solid
- modified release
- eg somatuline autogel
Summarise the use of implants in parenteral preparations.
- SC or IM
- pellets/rods
- sterile
- drug +/- excipients
- eg zoladex implant, nexoplanon, oxurdex (dexamethasone treats oedema), gliadel water
- act as reservoirs
- drug encapsulated in plastic/metal or non-biodegradable polymer
- drug released by osmotic pressure
- require surgical removal
