Parenterals Route Flashcards
What is parenterals route commonly referred as?
Drug administration by injection
What are the different routes?
Intravenous Intrathecal, epidural + intraspinal Intra-arterial + intracardiac Intradermal Subcutaneous Intramuscular Intra-articular Intra-ocular
What are the advantages?
Rapid onset of action
Delayed onset possible through intramuscular
Infusion of drugs for prolonged period
Avoids 1st-pass metabolism
Unconscious patients
Allows higher conc of drug in system/local
Why is it good that infusion of drugs is for prolong period?
Maintain steady-state plasma levels
Why is it good it avoids 1st-pass metabolism?
Improves bioavailability
What are the disadvantages?
Require professionals Potential risk Needle-stick injuries Poor patient acceptability Formulation + manufacture cost high Shelf-life shorter than oral Refrigerated = extra cost
Describe intravenous (IV)
Surface vein
1ml to several litres for infusion
Increases plasma drug conc
100% drug absorption
What is the infusion for intravenous?
Diluted in a bag = produces slow + controlled drug release rate
What emulsions cannot be used for IV?
W/O = block blood vessels
What do hypertonic/extreme drug pH solutions cause in IV?
Inflammation + pain at injection site
How is IV infused?
Central line into major vessel
= allows rapid diffusion by large blood vol
Describe intra-arterial
Like IV except via artery
More invasive + less accessible
Only used when no IV access
When may there be no IV access?
Premature babies
When is intracardiac used + why?
Only used life-threatening emergencies
= to produce rapid, local effect in heart
Describe intradermal
Inject into skin between epidermis + dermis
Up to 0.2ml
Absorption slow
Why is absorption slow in intradermal?
Little interstitial fluid to facilitate drug diffusion at injection site
= not-well perfused by blood
What is intradermal used for?
Immunological diagnostic tests + vaccinations
eg. BCG
Describe subcutaneous
Hypodermic injections
Inject into loose connective + adipose tissues below dermal skin layer
Where is subcutaneous injected + why?
Abdomen, upper arms/legs
= highly vascularised = absorption rapid + predictable
What can be injected subcutaneously?
Aq solutions or suspensions
Up to 1ml
What is an example of subcutaneous injection?
Insulin
Describe intramuscular
Into tissue of relaxed muscle = butt, thigh or shoulder
Up to 4ml
Slower than SC
What can be injected intramuscularly?
Aq or oily solutions or suspensions
What are the 2 intra-spinal routes?
Intrathecal
Epidural
Describe intrathecal
Cerebrospinal fluid (CSF) in subarachnoid space or spinal canal
100% absorption in CSF
Vol up to 10ml
What does intrathecal route allow drugs to do?
Bypass BBB
What are examples of intrathecal route into CSF?
Anticancer drugs
Antibiotics for meningitis
Analgesic
Describe epidural
Space between dura mater + vertebrae
Must be aq isotonic
Cannot include preservatives
What are examples of epidural?
Spinal anaesthesia - long-acting steroid
Describe intra-articular
Into synovial fluid of joint cavities
100% drug absorption at site of action
What is intra-articular suitable for?
Aq solutions/suspensions
What is an example of intra-articular route?
Anti-inflammatory drugs to treat arthritic conditions or sport injuries
What are the 2 routes for intraocular?
Intracameral
Intravitreal
What is the intraocular route?
Into eye
Describe intracameral
Into anterior chamber (front lens)
0.1-1ml
Antibiotics, local anaesthetics
Describe intravitreal
Into vitreous chamber
Treat ocular diseases
What precaution must be taken + why with intravitreal route?
Max vol 0.1ml
= minimise risk of rising intraocular pressure + damage
What must all parenteral preparations be?
Sterile
Why must be sterile?
Drug formulations directly injected into blood/body tissue
Why are excipients used?
Adjust isotonicity Adjust pH \+ drug solubility \+ drug stability \+ shelf-life Preservative
Why does isotonicity need to be adjusted?
To match human blood
What should excipients not do?
Adversely affect drug action or cause any side effects?toxicity
What are endotoxins?
Lipopolysaccharides found in outer membrane of gram-negative bacteria
What are pyrogens?
Substances that cause fever, typically produced by bacteria/viruses
What must parenteral preparations be free from?
Endotoxins + pyrogens
Particulates
What must all products comply with?
Tests for bacterial endotoxins + pyrogens
What can contain particulates?
IM
SC
Intra-articular
What happens if there is any suspended particles?
Travel through venous system to lung
= prevent blood flow
= pulmonary embolism
Why significantly can’t there be any particles in IV?
Droplet size of 3mm, which is equal to diameter of capillary
What must containers be?
Transparent Glass or plastic Airtight Effectively sealed Compatible with formulation
Why must a container be transparent?
So can inspect for particles
Why must container be effectively sealed?
To prevent contamination before use
What can sterile products be in?
Solutions
Suspensions
Emulsions
What must solutions be?
Clear
Free from particles
What must suspensions be?
Readily re-suspended on shaking
What does shaking suspensions enable?
Uniform dose to allow withdrawal
What must emulsions not be?
Show any signs of creaming or cracking
What are aq injections for?
Multiple dosing
What must aq injections contain?
Antimicrobial preservative
When can a preservative not be used in aq injection?
Dose vol bigger than 15ml
Injecting into eye or spine
What are unpreserved injections formulated in?
Single-dose containers
= in ampoules or prefilled syringes
What are infusions?
Sterile aq solutions/emulsions
What is the continuous phase as infusions?
H2O
What is the vol of infusions?
100-1000ml
Do infusions contain preservatives?
NO
What is isotonicity in respect with in infusions?
Blood
What are concentrates for?
Injection or infusion after solution
What are concentrates diluted with?
Saline or H2O for injection
How are concentrates administrated?
Through infusion bags
What are powders?
Dry sterile solid in final container for reconstitution
What is required for powders?
Vol of diluent added prior administration
When are powders used?
Used for drugs with short shelf-life after dissolved in solution
What are suspensions for?
SC
IM
Intra-articular
What do suspensions allow?
Slow + prolonged release = reduce dosing frequency
What must happen to suspended drug first?
Dissolved before it can be absorbed
Why may low aq solubility drugs use IM?
Provide prolonged effect
How long does benzylpenicillin benzathine IM suspension release over?
2-4 weeks
How long does hydrocortisone acetate IM suspension release over?
2-7 days
What are the vehicles for injections?
H2O = most common
Saline
Solubilising agents
Co-solvents
What type of H2O is vehicle for injection?
Highly purified grade
Describe saline
Up to 0.9% w/v
Commonly used as infusion vehicle
Why are solubilising agents added?
To aid dissolution
What is an example of solubilising agent?
Polyoxyethylene castor oil derivatives can solubilise hydrophobic drugs lie diazepam
What are examples of co-solvents?
Ethanol
Glycerol
Propylene glycol
Why are preservatives used?
Antimicrobial protection used in multi-dose
What are some common preservatives?
Benzalkonium chloride (0.01% w/v) Benzoic acid (0.17% w/v) Benzyl alcohol (1-2% w/v)
What do co-solvents do?
Aid dissolution + antimicrobial effect
What do antioxidants do?
Reduce drug degradation by oxidation = extend shelf-life
How do antioxidants work?
N2 gas bubbled through solution to displace O2
What can N2 be used for?
Fill container headspace
What is the physiological pH?
7.4
What is the pH range for injectables?
pH 3-9
What happens if pH is out of injectables range?
Too corrosive = tissue damage
What can adjust pH?
Acidifying + alkalizing agents
What maintains pH?
Buffers
When do buffers work best?
When pH is close to pKa of WA/WB
What is blood osmolarity?
275-295m Osm/kg
What is hypotonic?
Cells swell = burst
What is hypertonic?
Cells lose H2O = shrivel
What must IV infusions be?
Isotonic
What must also be ideally isotonic?
SC IM Intradermal CSF Intra-ocular
What is added to hypotonic?
NaCl
Dextrose
Mannitol
What can make it hypertonic?
Dilution prior administration
When are suspending agents used?
Used in suspensions to ensure drug can be readily re-suspended (by shaking) prior to use
What are examples of suspending agents?
Methylcellulose + polysorbates
How is a suspension re-suspended?
Shaking
What is the vol of glass ampoule containers?
1-10ml
What are glass ampoule containers used for?
Single-use unpreserved product
What glass is used for glass ampoule containers + why?
Type 1
= little interaction with formulation
What is problem with Type 1 glass?
Fragile = safety risk when opening
= deposition of glass particles when opening
What are advantages of plastic ampoule containers?
More robust
Safer to use
Fewer particles generated on opening
What are disadvantages of plastic ampoule containers?
More costly
More prone to drug interaction
What are vials made from?
Type 1 glass with re-usable synthetic drug closure
What is vol of vials?
5-100ml
What is the closure on vial?
Rubber closure held in place by aluminium cover seal
What are pros of rubber closure on vial?
Dust protection
Security measure
Self-sealing
Coated in Teflon = minimise drug interaction
What is the negative of rubber closer on vial?
Allows few punctures
What is vol of infusion bag?
100-1000ml
OR
3000ml
Describe collapsible infusion bag
Made from PVC or poly-olefin plastic
Have additive port = injectable drugs added
Air inlet not needed
Describe semi-rigid plastic bottle
Made of polyethene
Air equilibration may be required
Describe glass bottles
Less commonly used now
What different containers are used?
Glass ampoules Plastic ampoules Vials Infusion bags - collapsible Semi-rigid plastic bottles Glass bottles