Routes of Administration (Parenterals) Flashcards
What is parenteral administration?
- Drug administration other than via the GI tract (skin)
- Intravenous, Intrathecal, Intra-arterial, Intra dermal, Subcutaneous, Intramuscular, Intra-articular, intraocular
What is the intravenous route?
- Typically via a surface vein
- Rapidly increases plasma drug concentration (100%) drug absorption
- Water in oil emulsions can’t be administered as IV. Extreme pH or hypotonic (conc solution) causes inflammation
What are subcutaneous injections?
- Also called hypodermic
- Inject into loose connective and adipose (body fat) tissue, directly below dermal skin layer (typically abdomen/ upper arms)
What are intra arterial and intercardiac injections?
- Like IV but at an artery
- More invasive and less accessible than veins
- Intracardiac route is only used in life threatening emergencies : quick effect to heart
What are intradermal injections?
- Inject into skin between epidermis and dermis
- Absorption is low: little interstitial fluid to facilitate drug diffusion
- Used for vaccines
What are intramuscular injections?
- Inject into tissue of a relaxed muscle (shoulder)
- Aqueous or oily solutions can be administered
- Absorption = slower than subcutaneous
What are intraspinal route injections?
- Intrathecal: Directly into cerebrospinal fluid in subarachnoid space in spinal canal. Drugs bypass blood brain barrier
- Epidural: Into epidural space between dura mater and vertebrae
What is the intra articular injections?
- Given into the synovial fluid of joints cavities
- Suitable for aqueous solutions and suspensions
- 100% drug absorption at site
What is intraocular injections!
- Administed into eyes and subclassified into:
- intracameral
- intravitreal
What is intracameral injections?
- Into the anterior chamber CIN front of lens)
- from 0.1-1ml volumes
- local anaesthetics during eye surgery
What are intravitreal injections?
- Into the vitreous chamber
- to treat various ocular diseases
- max 0.1ml
What are the advantages of the parenteral route?
- Rapid onset of action
- avoids first puss hepatic metabolism, improves bioavailability
- suitable for unconscious patients
- allows higher concentration in the systemic circulation
What are the disadvantages of the parenteral route?
- Requires healthcare professional
- potential risks during administration/ needle injuries
- needle phobic
- shelf life= shorter
- requires refrigerator storage
Why should excipients be added?
- Adjust isotonicity to match human blood
- adjust ph
- increase drug solubility & stability
- increase shelf life
What are the different vehicles for injections?
- Water
- saline
- solubilising agents = aid drug dissolution (surfactants)
- Co-solvent
What are common preservatives in parenteral products?
- Benzalkonium chloride
- Benzoic acid
- Benzyl Alcohol
What are some co-solvents can aid drug solubility and have anti microbial effects?
- Ethanol
- Glycerol
- Propylene glycol
What do antioxidants do and what is sparging
- Reduce drug degradation by oxidation and extend shelf life
- Bubble nitrogen gas through drug solution to displace oxygen in the formulation
What are some antioxidants used?
- Vitamin C, E,
- Sodium metabisulphite, bisuphite, sulphite
What tonicity adjusting agents can be added to hypotonic and hypertonic solutions?
- Hypotonic: cells swell , NaCl, dextrose or mannitol
- Hypertonic: cells shrink, use dilutions
What suspending agents are commonly used?
- Methylcellulose and polysorbates
- Ensure drug can be readily suspended by shaking prior to use
What are pharmacopeial requirements of parenterals?
- Sterility
- Must be free from endotoxins and pyrogens
- Except suspensions for IM, SC or intra articular routes, all products must be free of visible particles: will travel through venous system to lung, preventing blood flow
What are Endotoxins?
- Are lipopolysaccharides found in the outer membrane of gram negative bacteria
What are Pyrogens?
- Are substances that cause fever, typically produced by bacteria or viruses
What are category specific requirements for injections?
- Solutions: must be clear & free from visible particles
- Suspensions: readily resuspended on shaking
- Emulsions: No creaming or cracking
- Contain antimicrobial preservative
- Unpreserved injections are formulated in single dose containers
What are category specific requirements for infusions?
- Sterile
- Water as continuous phase
- Isotonic
- Typical volume 100-1000ml
- No preservatives
What are category specific requirements for concentrates for injections and infusions?
- After dilution can be used (usually with saline and administered in infusion bags)
What are category specific requirements for powders for injections or infusions?
- Dry sterile solid in final container for reconstitution
- Required volume of diluent is added prior to administration
- Short shelf life
Which different formulations require the drug to be dissolved before absorption?
- SC, IM, Intra articular
- Allows slow and prolonged release : reduce dose frequency
What are the requirements of containers?
- Made from glass or plastic
- Effectively sealed to prevent contamination
- Airtight
What are the different containers used?
- Glass ampoules: Single use
- Plastic ampoules: more robust, more prone to drug adsorption
- Vials: Rubber closure held in place by aluminium cover, dust protection
- Infusion bags/ bottles: large volumes packaged in collapsible infusion bags, semi rigid plastic bottles, glass bottles
What is the physiological pH, acceptable pH for injections and how can pH be adjusted?
- 7.4
- 3-9 (pH outside range is corrosive and causes tissue damage)
- Acidifying agents: hydrochloric
- Alkalizing agents: sodium bicarbonate
