Routes of Administration I

Question 1

What questions would you ask when developing medicine?

Answer 1

Purpose of API, Which disease and location. best ROA, best dosage form

Question 2

Describe systemic delivery

Answer 2

Drug delivery to site other than that it’s applied to - Pass through systemic circulation to target organ

Question 3

Describe local delivery

Answer 3

Drug delivery directly to site of action

Question 4

Describe disadvantages of systemic delivery

Answer 4

Side effects throughout entire body, exposed to infection

Question 5

Describe advantages of local delivery

Answer 5

Inc conc at site, side effects only occur at side

Question 6

What dosage form would you administer drug Terbinafine to treat Athlete’s foot?

Answer 6

Local delivery of an API in topical cream dosage form, if infected also give antibiotics (Alternate: Gel/spray)

Question 7

What dosage form would you administer Salbutamol to treat an asthma attack?

Answer 7

Local delivery to the lungs via asthma pump to reach alveoli

Question 8

What dosage form would you administer Mesalazine to treat Crohn’s disease (Colon ulcer)>

Answer 8

Local delivery to colon with oral tablets/capsules dosage form to reduce spread

Question 9

What dosage form would you administer Sodium Valproate to treat epilepsy?

Answer 9

Systemic delivery via bloodstream with oral tablets (b-blockers) to target optical receptors (Also: IV)

Question 10

Describe the difference between enteral vs parental delivery?

Answer 10

Enteral - Administration via GI tract

Parenteral - Mainly IV, all other routes eg ocular, nasal, transdermal, pulmonary

Question 11

In all cases except IV, how do drugs reach bloodstream?

Answer 11

Pass biological barrier (membrane of liver via first pass metabolism) = Causes less drug to enter blood

Question 12

Describe topical routes

Answer 12

Applied to the surface of the body, can be local or systemic effect eg topical cream vs transdermal patch

Question 13

Describe mucosal routes

Answer 13

Some topical routes are mucosal routes

Mucosal = Wet surfaces of the body that secrete mucous

Question 14

Name systemic vs local mucosal treatments

Answer 14

Local - Buccal treatment for mouth ulcer (bonjela)

Systemic - Rectal if babies can’t swallow orally

Question 15

What 3 factors influence the choice of dosage form?

Answer 15

Scientists/Clinicians - Best opinionated treatment
Patients - Compliance, preference, ease
Manufacturers - Transport, cost

Question 16

Define onset of action

Answer 16

Speed at which the drug action starts according to the ROA and dosage form

Question 17

Describe the types of dosage form associated with each time of onset

Answer 17

Seconds - IV
Minutes - IM, SC, buccal, aerosol
Minutes-hours - Solutions, suspension, powders, capsules, granules
Hours - Enteric-coated formulations
Days - Depot injections
Varies - Topical formulation

Question 18

Describe why subcutaneous injections only take minutes

Answer 18

Means just under the skin so rapid onset eg for insulin

Question 19

Describe why powders take minutes-hours

Answer 19

Tablets need to dissolve/break down before absorption

Question 20

What is an enteric-coated formulations and why does it take hours?

Answer 20

Tablets coated to control when and where it is dissolved/absorbed, specifically to SI via pH response

Question 21

Briefly describe LADME

Answer 21

Liberation - Drug passage from dosage form
Absorption - Drug uptake to bloodstream across SI
Distribution - Drug moving from abs site to target site
Metabolism - Drug interaction modified
Excretion - Elimination via kidneys (urine/faeces via liver/GIT)

Question 22

Describe liberation in detail

Answer 22

Removal of drug from tablet to dissolve before it reaches system

Question 23

Describe metabolism in detail

Answer 23

Body changes drug chemistry (activation) via GI fluid with enzymes

Question 24

Is a drug absorbed and excreted at the same rate?

Answer 24

No

Question 25

How do you determine drug systemic availability?

Answer 25

Measuring plasma conc with time

Question 26

Describe a plasma conc vs time graph

Answer 26

Absorption causes rapid inc in plasma conc until Cmax, slowly declines as elimination occurs (wide bell shape)

Question 27

What does Cmax show?

Answer 27

The maximal conc of drug abs into the blood, no more drug left to abs

Question 28

Define bioavailability

Answer 28

Measurement of rate and extent of active drug reaching systemic circulation, available at site of action for an effect

Question 29

When would the bioavailability be low?

Answer 29

If a systemic drug is metabolised into an inactive form

Question 30

Briefly define hepatic first pass metabolism (HFPM)

Answer 30

Reduces extent of absorption of drug

Question 31

Describe how HFPM occurs

Answer 31

Presystemic metabolism (before drug's in blood) Abs via gut, enter blood via portal circulation Transported to liver Metabolised by liver enzymes (drug now inactive) Destruction by liver = HFPM

Question 32

Which dosage forms are affected by HFPM?

Answer 32

Enteral delivery - Oral tablets become inactive if abs by liver Parenteral - IV don't enter portal circulation

Question 33

What happens to drugs in the body?

Answer 33

Pharmacokinetics | Drug absorbed, enter blood, either distributed to tissues/receptor sites, metabolised or excreted

Question 34

What do barriers within the body cause?

Answer 34

Dec permeation = Dec rate/extent of abs = Dec bioavailability