D4. Routes of administration Flashcards
examples of direct administration?
-topical creams/ solutions e.g Antifungals and Keratolytics
-eye drops e.g glaucoma and Ophthalmological tools
-intravenous infusion e.g blood disorders, sepsis
Describe the inhalation route of administration
-Gaseous or volatile drugs
-Nebulized solutions
-Useful for lung problems (e.g. COPD, asthma)
-Absorption via lung possible for other conditions and formulations (even proteins)
advantages of direct application?
-Rapid and local effect
-No loss to first-pass metabolism
-Reduced risk of systemic side effects
disadvantages of direct application?
-Not possible for “internal” targets
-Can be difficult to self-administer
-Dosing more complex than oral or injection
-Systemic absorption will still occur (esp. from eyes and lungs)
What is a hypodermic injection?
A hypodermic injection is a shot given into the skin or tissues beneath the skin
ONE NOTE
What is an intravenous injection?
-Injection into vein
-Solutions are the only practical formulation
Advantages of an intravenous injection?
-Absorption circumvented
-Very rapid (potentially immediate) onset of action
-Suitable for large volumes
-Permits careful titration of dose
Disadvantages of an intravenous injection?
-Risk of serious adverse effects (embolism)
-Not suitable for oily/poorly soluble substances
what is an intramuscular injection?
-Injection into muscle parenchyma
-Solutions, suspensions, solid (implant)
advantages of an intramuscular injection?
-Prompt absorption into systemic circulation
-Formulation can modify release kinetics (repository preparations)
-Suitable for oily vehicles
Disadvantages of an intramuscular injection?
-Painful
-Danger of nerve damage
what is a subcutaneous injection?
-Injection into adipose tissue layer
-Solutions, suspensions, solid (implant)
advantages of subcutaneous injection
-injection into adipose tissue layer
-Solutions, suspensions, solid (implant)
advantages of a subcutaneous injection?
-Prompt absorption into systemic circulation
-Formulation can modify release kinetics (repository preparations)
-Suitable for some poorly soluble suspensions
Disadvantages of a subcutaneous injection?
-Risk of pain or necrosis from irritating substances
-Not suitable for large volumes
What is an intrathecal injection?
-Injection into sub-arachnoid space in spinal column
-Solutions, suspensions
Advantages of an Intrathecal injection?
-Bypasses BBB
-Direct access to cerebrospinal fluid
Disadvantages of an Intrathecal injection?
-Requires technically skilled staff
-Not suitable for many drugs, or additives to formulations (e.g. preservatives)
-Sterility essential
what is an epidural?
-Injection into subdural cavity in spinal column
-Solutions (anaesthesia and painkillers)
Advantages of an epidural?
-Localised effect
-Direct access to spinal cord
Disadvantages of an epidural?
-Requires technically skilled staff
-Not suitable for many drugs, or additives to formulations (e.g. preservatives)
-Sterility essential
Describe the transdermal route?
-Topical cream or surface patch allows diffusion through epidermis
-Microneedle patches penetrate into deeper layers of epidermis
-Absorption in blood supply to skin
what are G.I routes of administration?
-Sublingual (under tongue) and buccal (cheek) e.g Tablets, wafers
-Oral e.g Tablets, Capsules, Solutions, suspensions, syrups
-Rectal e.g Suppository (solid), Enema (solution)
advantages for oral administration?
-Economical
-Easy to self-administer
-Multiple formulations possible
disadvantages of oral administration?
-Loss due to first pass metabolism
-Incomplete absorption
-Need compliant and conscious patient
-Not suitable with GI disease, nausea or vomiting
Intraperitoneal meaning?
Injection into body cavity (through peritoneum)
Intraosseous meaning?
Infusion into bone marrow (non-collapsible, used when i.v. impractical)
Vaginal meaning?
Direct application for antifungal pessaries, but also possible for systemic absorption
Enteral meaning?
Delivery through GI tract routes
Parenteral meaning?
Delivery through non-GI routes
administration variation across the life span?
-Newborns have difficulty with oral routes, rectal route can be helpful
-I.V. also more difficult in newborns, Intraosseous a possibility in extreme cases
-Children can struggle with swallowing tablets, syrups and solutions preferable
-G.I. disorders increase with age, oral routes become less reliable
what is a bolus injection?
Intravenous injection of a small volume
Describe the time course for an intravenous injection?
-Immediate onset
-Exponential decline due to elimination mechanisms
ONE NOTE
Describe intravenous infusion
-Concentration rises until rate of infusion and rate of elimination are matched
-Time to steady state (Css) ~4-5 half lives for elimination
-Steady state will not be reached with shorter infusion times
ONE NOTE
Rate and extent of absorption depends on what?
-Rate and extent of absorption depends on blood supply and path to systemic circulation
-Intravenous fastest, oral slowest (and greatest chance of loss)
-Elimination similar in all cases
