D4 Routes of administration

Question 1

give 3 examples of direct administration methods

Answer 1

topical creams / solutions
eye drops
intravenous infusion

Question 2

give 2 examples of types of medicines used by topical creams / solutions and their specific uses

Answer 2

• antifungals (to treat things such as ringworm)
• keratolytics (to treat warts, veruccas etc.)

Question 3

2 indications that may need something administered via intravenous infusion

Answer 3

• blood disorders (eg. heparin can reduce risk of thrombosis)
• sepsis

Question 4

describe the inhalation route of administration and what it can be used to target

Answer 4

• can be for gaseous or volatile drugs or nebulised solutions
• useful for long problems eg. COPD, asthma
• absorption via lung possible for other conditions (there are capillaries surrounding alveoli so route can target other things eg. used for general anaesthetic which targets the brain)

Question 5

advantages of direct application

Answer 5

• rapid and local effect
• no loss to first pass metabolism
• reduced risk of systemic side effects

Question 6

disadvantages of direct application

Answer 6

• not possible for ‘internal’ targets
• can be difficult to self-administer
• dosing more complex than oral or injection
• systemic absorption will still occur (especially from eyes and lungs)

Question 7

describe hypodermic injection

Answer 7

needle will generally be located in the hypodermis

Question 8

describe intravenous injection

Answer 8

• injection into vein
• solutions are the only practical formulation
• cannot inject suspensions or oily mixtures

Question 9

advantages of intravenous injection

Answer 9

• absorption circumvented
• very rapid (potentially immediate) onset of action
• suitable for large volumes (can infuse into the vein over a long period of time for large volume)
• permits careful titration of dose

Question 10

disadvantages of intravenous injection

Answer 10

• risk of serious adverse effects (embolism)
• not suitable for oily / poorly soluble substances
• will need trained expert to deliver this route safely and effectively

Question 11

describe intramuscular injection

Answer 11

• injection into muscle parenchyma (solutions, suspensions, implant (solid))
• needle goes all the way through tissue

Question 12

advantages of intramuscular injection

Answer 12

• prompt absorption into systemic circulation
• formulation can modify release kinetics (repository preparations)
• suitable for oily vehicles

Question 13

disadvantages of intramuscular injection

Answer 13

• painful
• danger of nerve damage
• will need trained expert to deliver this route safely and effectively

Question 14

describe subcutaneous injection

Answer 14

• injection into adipose tissue layer
• solutions, suspensions, solid (implant)

Question 15

advantages of subcutaneous injection

Answer 15

• prompt absorption into systemic circulation
• formulation can modify release kinetics (repository preparations)
• suitable for some poorly soluble suspensions

Question 16

disadvantages of subcutaneous injection

Answer 16

• risk of pain or necrosis (death of body tissue) from irritating substances
• not suitable for large volumes
• will need trained expert to deliver this route safely and effectively

Question 17

describe intrathecal injection

Answer 17

• injection into subarachnoid space in spinal column
• solutions, suspensions

Question 18

advantages of intrathecal injection

Answer 18

• bypasses BBB
• direct access to cerebrospinal fluid (drug can get to brain without having to cross BBB so gives better access and wider range of drugs can be used)

Question 19

disadvantages of intrathecal injection

Answer 19

• will need trained expert to deliver this route safely and effectively
• not suitable for many drugs or additives to formulations eg. preservatives
• sterility is essential

Question 20

if an intrathecal injection is not sterile, what can it cause?

Answer 20

meningitis

Question 21

describe epidural injection

Answer 21

• injection into subdural cavity in spinal column
• solutions (anaesthesia and painkillers)

Question 22

advantages of epidural injection

Answer 22

• localised effect
• direct access to spinal cord

Question 23

disadvantages of epidural injection

Answer 23

• need trained expert to deliver this route safely and effectively
• not suitable for many drugs or additives to formulations eg. preservatives
• sterility is essential

Question 24

describe the transdermal route of administration. what is the difference between the orange and the blue in the image?

Answer 24

orange: topical cream or surface patch
- allows diffusion through epidermis

blue: micro needle patches
- penetrate into deeper layers of epidermis

• absorption in blood supply to skin
• factors like temperature can make this blood supply vary

Question 25

state 4 GI routes of administration

Answer 25

- sublingual (under tongue) - buccal (cheek) - oral - rectal

Question 26

advantage of rectal route of administration

Answer 26

blood supply doesn't go via hepatic portal system so no first pass through the liver

Question 27

advantages for oral route of administration

Answer 27

- economical - easy to self-administer - multiple formulations possible

Question 28

disadvantages for oral route of administration

Answer 28

- loss of dose due to first pass metabolism - incomplete absorption, failure to absorb across gut wall - need compliant and conscious patient - not suitable with GI disease, nausea or vomiting

Question 29

what is the intraperitoneal route of administration?

Answer 29

- injection into body cavity (through peritoneum of abdomen) - bypass vascular system

Question 30

what is the intraosseous route of administration?

Answer 30

- infusion into bone marrow (non-collapsible, used when IV is impractical) - used if veins are collapsing because bone will not collapse

Question 31

what is the vaginal route of administration used for?

Answer 31

direct application for anti fungal pessaries but also possible for systemic absorption of drug into blood supply

Question 32

what is the enteral route of administration?

Answer 32

delivery through GI tract routes

Question 33

what is the parenteral route of administration?

Answer 33

delivery through non GIT routes

Question 34

describe and explain the variations in administration methods throughout a lifetime

Answer 34

- newborns have difficulty with oral routes (rectal can be helpful and less distressing) - IV is also more difficult in newborns (intraosseous is a possibility in extreme cases) - children can struggle with swallowing tablets (syrups and solutions are preferable) - GI disorders increase with age so oral routes becomes less reliable

Question 35

describe the time course for intravenous injection

Answer 35

- bolus (fixed, small, intravenous) volume of solution

Question 36

describe how concentration changes during intravenous infusion

Answer 36

- rises until rate of infusion and rate of elimination are matched - this means steady state concentration has been reached

Question 37

what is Css in terms of intravenous infusion?

Answer 37

- time to steady state (Css) - around 4-5 half lives is the time it takes for elimination - not affected by infusion rate, only affected by elimination rate - infusion rate only affects the concentration at which steady state is reached - steady state will not be reached faster with shorter infusion times

Question 38

what is the slowest route of administration? what other feature does it have?

Answer 38

- oral is slowest - also has the greatest chance of loss

Question 39

compare and contrast the time profile graphs for the IV, intramuscular and oral route of administration

Answer 39

- IV is exponential decline - oral has longest Tmax and lowest Cmax