routes of administration (parentals) Flashcards
what is parental administration
administration in ways other than via the GI tract
so e.g
intravenous
intrathecal, epidural and intraspinal
intradermal
subcutaneous
intramuscular
intra-articular
intraocular
what is the intravenous route 1
- Typically via a surface vein.
- From 1ml ‘injection’ up to several liters for ‘infusion’.
- IV injection rapidly increases plasma drug concentration.
- Provide 100% drug absorption.
- Infusion (drug is diluted in an infusion bag) provides a slow and controlled drug release.
intravenous route 2
- Water-in-oil emulsions or suspensions cannot be administered via IV as oil phrase or suspended drugs can block blood vessels.
- Hypertonic or extreme pH drug solutions can cause inflammation and pain at injection site.
– Plasma osmolality measures
the body’s electrolyte–water
balance.
– Blood has an osmolality of
275-295 mmmol/kg.
5
subcutaneous injections
- Also called hypodermic injections.
- Inject into the loose connective and adipose tissues immediately below the dermal skin layer.
- Typically in the abdomen, upper arms/legs.
- Highly vascular site, so absorption is rapid and
predictable. - Aqueous solutions or suspensions can be administered.
- Volumes up to 1 ml.
- E.g. insulin
intra-arterial and intracardiac injections
- Intra-arterial is like IV administration except it is via artery.
– More invasive and less accessible than via the veins.
– Only used when IV access cannot be established e.g. pre-mature babies. - Intracardiac route is used only in life-threatening emergencies to produce a rapid, local effect in the heart.
intradermal injections
inject into the skin between the epidermis and dermis
limited to volumes of 0.2ml
absorption is low
used for immunological diagnostic tests and vaccinations e.g BCG
intramuscular injections
*inject into the tissue of a relaxed muscle in buttock, thigh and shoulder
*aq or oily solutions or suspensions can be administered
*volume up to 4ml
intraspinal injection
-intrathecal injection
-given into cerebrospinal fluid (CSF) in the subarachnoid space or spinal canal
-allow drugs to bypass the blood-brain barrier
-100% drug absorption into the CSF
- volume up to 10ml
-e.g anticancer drugs, antibiotics for meningitis, analgesic
intrapsinal injections
-epidural injection
-given into the epidural space between the dura mater and the vertebrae
e.g spinal anesthetics, long-acting steroid
All intraspinal injections must be isotonic aqueous solutions and cannot include preservatives
intraarticular injections q
-given into the synovial fluid of joints cavities
-suitable for aq solutions and suspensions
for anti-inflammatory drugs to treat arthritic conditions or sports injuries
-100% drug absorption at this site of action
intraocular injections
-intracameral injections
-intravitreal injections
administration of drug into the eyes
*intracameral injections
-into the anterior chamber (in front of lens)
-from 0.1ml to 1ml volume
for antibiotics, local anesthetics during eye surgery
*intraviteral injections
-into vitreous chamber
- to treat various oscular disease
-maximum volume 0.1ml, to minimize risk of rising intraocular pressure and damaged retina
advantages of parental administration routes
-most routes allow rapid onset action
-avoids first pass hepatic metabolism improving bioavailability
-allows a higher concentration of drug in systematic circulation or local site
- suitable for unconscious patients, or unable to administer orally
-delayed onset action is possible through intramuscular injection
-infusion of drugs for prolonged period is possible to maintain steady-state plasma levels
disadvantages of parental routes of administration
-usually requires healthcare professionals to administer
-needle stick injuries
-needle phobia and poor patient acceptability
- formulation and manufacturing costs are higher requiring a sterile and highly controlled pyrogen-free environment
-shelf life is usually shorter than oral forms
-often requires refrigerated storage at extra costs
reasons for addition of excipients
-adjust isotonicity to match human blood
-adjust pH
-increase drug solubility
-increase drug stability
-increase shelf life
*they shouldnt affect drug actions or cause side effects
injection vehicles
- “Water for injections” is the most common vehicle.
– Highly purified grade of water. - “Saline for injections”
– is available in a variety of strength up to 0.9%w/v (isotonic).
– Commonly used as infusion vehicle. - Solubilising agents may be added to aid drug dissolution.
– Surfactants e.g. polyoxyethylene castor oil derivatives can solubilise hydrophobic drugs like diazepam.
– Oil-in-water emulsions using emulsifying agent like lecithin.
– α- and γ- cyclodextrins. - Co-solvent system may be used.
– E.g. ethanol, glycerol, propylene glycol.
