Parentral delivery devices Flashcards
what are the classifications of parenteral preparation
IV
IM
SC
parenteral preparations
According to formulation
Emulsions
Suspensions (not for IV)
Solutions
According to volume
Small Volume <10ml
Large volume >10ml
what are the pharmaceutical consideration factprs
Vehicles
Solubility
Preservatives
Osmolarity and pH
Viscosity
what are the advantages and disadvantages of Parentral drug delivery
Rapid & complete absorption
predict the PK profile of drug control dose & frequency
For the unconscious patient, uncooperative patient, nausea /vomiting; unable to swallow
Useful for giving very small dose
But…
Aseptic precautions must be followed
Manufacturing of PD is more expensive
Once administered cannot be removed from bloodstream
Pain & infection at site of injection can occur
what are injection techniquies
Volume depends on onset and rate required.
Larger volumes allow sustained release while bolus injections (small volume) is for immediate onset
The type of formulation depends mainly on solubility of drug
90 into sub tissue or 45 degrees - sub
15 dgrees - intradermal
72- intamuscular or 90 but deeper into the skin
when is IV used?
Large (up to 500ml) or small volumes (<10ml) can be administered
Solutions or emulsions (droplet size below 1microM)
Suspension must not be administered (Why?)
Not to administer larger volume at fast rate sudden osmotic pressure change/electrolytes imbalance risk of shock or acute renal failure
E.g. gentamicin IV
what are the complications associated with IV?
Air embolism, or the injection of air into a vessel
Thrombosis, the formation of a clot in a blood vessel
Haemolysis, the breakdown of red cells with the release of haemoglobin, can cause kidney damage if severe.
Phlebitis is the inflammation of the vein wall due to irritation from the formulation; it can be caused by the formulation itself, or may be due to precipitation of the drug if injection is too rapid
Extravasation, or the leakage of the injection from the vein into the surrounding tissue: particular problem for cytotoxic materials, (e.g. methotrexate or mitomycin)
when is IM route used
sites
Small volumes (<10ml) can be administered
Commonly used for sustained release-onset not important
Typical sites : deltoid (vaccines), gluteal or vastus lateralis (EpiPen)
Onset<IV>SC but choice depends on desired onset & mw
E.g. NSAIDS, Flu vaccine</IV>
what is the SC route and when is it used
sites
Into the fat layer, beneath dermis and epidermis and above muscle tissue
Slower absorption, usually low volume (1mL)
Typical sites: arm, abdomen, legs
Insulin is most common example
Other examples local anaesthetics lidocaine 5% (with adrenaline), enoxaparin (Clexane®)-should not be given IM-haematoma
Drugs injected subcutaneously dissolve in the interstitial fluid and gain entry to the bloodstream by two routes:
-They may be absorbed directly into blood vessels, but the subcutaneous tissues are often adipose and poorly perfused
-the interstitial fluid is collected by lymphatic capillaries and these drain into the regional lymph nodes and then into the bloodstream
These pathways are both relatively slow and depend on the local vasculature, so absorption from subcutaneous sites can be slow and unpredictable.
what are insulin delivery methods
Insulin Syringe
Insulin Pen
Insulin Pump or Pod
Jet Injector
what is BOLUS insulin
it is timed and amount is given based on food intake
what are the insulin types available?
Humalog (lispro).
Lantus: (Glargine): usually od
Levemir: (Detemir) often bd
Novorapid: Begins working after 10-20 minutes, and will last for between 3 and 5 hours, usually tds.
Insulatard: human isophane (NPH) insulin.
vehicles for injections
Water for injections
Appearance
Purity
Sterility (water for injections BP is sterile)
Absence of pyrogens and particulates
Pyrogen free
Non-aqueous vehicles
Used for water-insoluble APIs- must be inert and safe
Typically oils (corn oil, cottonseed oil) or water miscible solvents (propylene glycol/ethanol for digoxin)
Issues (pain/irritation on injection; patients sensitivity)
how does solubility effect drufs
Poorly soluble drug more likely be emulsion or suspension
Co-solvents can be used such as ethanol, PEG, glycerine, soybean oil and castor oil
Surfactants can be used, but toxicity profile should be carefully evaluated, Polyoxyethylene sorbitanmonooleate (Tween 80), Sorbitan monooleate Polyoxyethylenesorbitan monolaurate (Tween 20), Lecithin
Pre-formulation approach- e.g. ondansetron hydrochloride dihydrate
what should preservatives be avoided in
Preservatives should be avoided in single dose IV and not allowed in IT and ED
If desired (multidose) phenolic compounds, e.g. phenol (0.25–0.5% w/v) or chlorocresol (0.1–0.3% w/v), methylparahydroxybenzoic acid
effects of osmolarity and pH
Isotonicity is deemed not clinically relevant-slow IV infusion render hypertonic liquids isomolar, however hypotnicity should be corrected by dextrose, glycerine or NaCl- Check BNF and British Pharmaceutical Codex
To maintain pH, to ensure drug stability and prevent possible precipitation
Buffers include acetic acid/sodium acetate, citric acid/sodium citrate and sodium phosphate/disodium phosphate
