D4. Routes of administration

Question 1

examples of direct administration?

Answer 1

-topical creams/ solutions e.g Antifungals and Keratolytics
-eye drops e.g glaucoma and Ophthalmological tools
-intravenous infusion e.g blood disorders, sepsis

Question 2

Describe the inhalation route of administration

Answer 2

-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)

Question 3

advantages of direct application?

Answer 3

-Rapid and local effect
-No loss to first-pass metabolism
-Reduced risk of systemic side effects

Question 4

disadvantages of direct application?

Answer 4

-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)

Question 5

What is a hypodermic injection?

Answer 5

A hypodermic injection is a shot given into the skin or tissues beneath the skin
ONE NOTE

Question 6

What is an intravenous injection?

Answer 6

-Injection into vein
-Solutions are the only practical formulation

Question 7

Advantages of an intravenous injection?

Answer 7

-Absorption circumvented
-Very rapid (potentially immediate) onset of action
-Suitable for large volumes
-Permits careful titration of dose

Question 8

Disadvantages of an intravenous injection?

Answer 8

-Risk of serious adverse effects (embolism)
-Not suitable for oily/poorly soluble substances

Question 9

what is an intramuscular injection?

Answer 9

-Injection into muscle parenchyma
-Solutions, suspensions, solid (implant)

Question 10

advantages of an intramuscular injection?

Answer 10

-Prompt absorption into systemic circulation
-Formulation can modify release kinetics (repository preparations)
-Suitable for oily vehicles

Question 11

Disadvantages of an intramuscular injection?

Answer 11

-Painful
-Danger of nerve damage

Question 12

what is a subcutaneous injection?

Answer 12

-Injection into adipose tissue layer
-Solutions, suspensions, solid (implant)

Question 13

advantages of subcutaneous injection

Answer 13

-injection into adipose tissue layer
-Solutions, suspensions, solid (implant)

Question 14

advantages of a subcutaneous injection?

Answer 14

-Prompt absorption into systemic circulation
-Formulation can modify release kinetics (repository preparations)
-Suitable for some poorly soluble suspensions

Question 15

Disadvantages of a subcutaneous injection?

Answer 15

-Risk of pain or necrosis from irritating substances
-Not suitable for large volumes

Question 16

What is an intrathecal injection?

Answer 16

-Injection into sub-arachnoid space in spinal column
-Solutions, suspensions

Question 17

Advantages of an Intrathecal injection?

Answer 17

-Bypasses BBB
-Direct access to cerebrospinal fluid

Question 18

Disadvantages of an Intrathecal injection?

Answer 18

-Requires technically skilled staff
-Not suitable for many drugs, or additives to formulations (e.g. preservatives)
-Sterility essential

Question 19

what is an epidural?

Answer 19

-Injection into subdural cavity in spinal column
-Solutions (anaesthesia and painkillers)

Question 20

Advantages of an epidural?

Answer 20

-Localised effect
-Direct access to spinal cord

Question 21

Disadvantages of an epidural?

Answer 21

-Requires technically skilled staff
-Not suitable for many drugs, or additives to formulations (e.g. preservatives)
-Sterility essential

Question 22

Describe the transdermal route?

Answer 22

-Topical cream or surface patch allows diffusion through epidermis
-Microneedle patches penetrate into deeper layers of epidermis
-Absorption in blood supply to skin

Question 23

what are G.I routes of administration?

Answer 23

-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)

Question 24

advantages for oral administration?

Answer 24

-Economical
-Easy to self-administer
-Multiple formulations possible

Question 25

disadvantages of oral administration?

Answer 25

-Loss due to first pass metabolism -Incomplete absorption -Need compliant and conscious patient -Not suitable with GI disease, nausea or vomiting

Question 26

Intraperitoneal meaning?

Answer 26

Injection into body cavity (through peritoneum)

Question 27

Intraosseous meaning?

Answer 27

Infusion into bone marrow (non-collapsible, used when i.v. impractical)

Question 28

Vaginal meaning?

Answer 28

Direct application for antifungal pessaries, but also possible for systemic absorption

Question 29

Enteral meaning?

Answer 29

Delivery through GI tract routes

Question 30

Parenteral meaning?

Answer 30

Delivery through non-GI routes

Question 31

administration variation across the life span?

Answer 31

-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

Question 32

what is a bolus injection?

Answer 32

Intravenous injection of a small volume

Question 33

Describe the time course for an intravenous injection?

Answer 33

-Immediate onset -Exponential decline due to elimination mechanisms ONE NOTE

Question 34

Describe intravenous infusion

Answer 34

-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

Question 35

Rate and extent of absorption depends on what?

Answer 35

-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