Applied Pharmacokinetics: Routes of Administration

Question 1

Name 3 routes of drug administration.

Answer 1

1. Oral
2. Rectal
3. Parenteral

Question 2

What’s the limiting factor of oral drug administration

Answer 2

Absorption feom GIT

Question 3

In which clinic setting is oral meds not absorbed?

Answer 3

1. Critically ill patients
2. Postoperative ileus

Question 4

Name factors that enhance or impair GI drug absorb

Answer 4

1. Acidic drugs are non-ionized and, therefore, well absorbed
2. Absorption area stomach small vs intestine
3. Enhanced gastric emptying increase absorption vs. delayed GI emptying
4. Tablet formulation

Question 5

What factor affected by tablet Formulation?

Answer 5

Bioavailability

Question 6

Name types of drug formulations.

Answer 6

1. Powder form
2. Solid formulation
3. Micronization
4. Enteric coated tablets
5. Sustained-release formulation.

Question 7

Describe effects of tablet formululation on bioavailability of the active content; Powder- filled gelatine formulation

Answer 7

Fastest and most reliable as the shell desolves rapidly within the stomach

Question 8

Describe effects of tablet formululation on bioavailability of the active content: Solid formulation

Answer 8

It has to disintegrate

Question 9

Describe effects of tablet formululation on bioavailability of the active content: Microionization

Answer 9

Particle size is reduced. Therefore, the surface area of the drug is increased, which is exposed to the solvant

Question 10

Describe effects of tablet formululation on bioavailability of the active content : Enteric coated

Answer 10

• Coat canbe gum/wax/cellulose
• these dissolve in an alkaline environment, i.e., small intestine, therefore abortion is delayed for hours

Example aspirin

Question 11

Describe effects of tablet formululation on bioavailability of the active content : sustained-release formulation

Answer 11

• Allows release over extended period
•The dosing frequency is reduced
• keeps plasma concentration relatively static
• Contraindicated in drugs with long half lives

Question 12

What are the characteristics of rectal drug administration

Answer 12

1. Absorption incomplete and unpredictable
2. Plasma concentration 80-90% that of oral formulation
3. Good blood supply but small surface area no Villi in rectum
4. Lower rectum Bypasses portal system therefor Avoids presystemic elimination
5. Upper rectum frains into portal system

Question 13

3 Uses of rectal drug administration

Answer 13

1. Pediatric
2. Unconscious patient with no iv access
3. Persistent vomiting

Question 14

Give examples of drugs given PR by anaesthetist.

Answer 14

Analgesics : PARACETAMOL, NSAIDS, tramadol.
Antipyretics: paracetamol
Antiemetics: cyclizine, procloperazine
Sedatives: ketamin, Diazepam (rarely)

Question 15

Caution with rectal drug administration

Answer 15

1. Informed consent
2. Not use in shocked patients poor blood supply.

Question 16

Name 8 parenteral route of drug administration

Answer 16

1. Percutaneous
2. Mucosal
3. Subcut & IM
4. IV
5. Intra-arterial
6. Neurexial
7. Intraneural
8. Intrapleural and intra-articular

Question 17

What are the 2 routes for percutaneous drug administration?

Answer 17

1. Transdermal
2. Mucosal

Question 18

Percutaneous

Answer 18

Skin thick with keratin
Little water and fat
Acts as barrier to both water soluble and fat soluble drugs.

Question 19

Transde

Answer 19

Absorption depends on
1. Surface area and
2. lipid solubility
Therefore ideal for small lupophilic molecules that need low absorption rate to achieve satisfactory plasma concentration.
3. Caution skin allergy and toxic systematic absorption

Question 20

Transdermal: iontophoresis

Answer 20

Substance carrying a charge delivered/ propelled through skin by low electric current

Question 21

Nasal mucosa characterist

Answer 21

Absorption occurs readily
Ideal for pediatric premed except for midaz
Ideal route for:
• Desmopressin SIADH
• Cocain vasocostrictive toxic dose 2-3 mg/kg

Question 22

Buccal mucosa

Answer 22

Highly Vascular ideal for fat soluble drugs
Venous drainage goes directly to systemic circulation bypassing 1st pass metabolism
Fentanyl lollipop

Question 23

Sublingual mucosa

Answer 23

Small surface area
Highly vascular
Absorption variable and affected by
•Time in the mouth
• how rapid drug dissolves
• salava flow
3. Route Avoids intestinal destruction and 1st pass metabolism

Examples, propranolol, nifedipine, nitroglycerin spray

Question 24

Pulmonary mucosa

Answer 24

Absorption via alveolar capillary with thin membranes
Avoids QST pass metabolism
Small inhaled particles suspended in air and not precipitate

Adrenaline no longer recommended in this route

Question 25

Subcut and IM

Answer 25

Diffusion gradient required Determined by regional blood flow and solubility of drug in Interstitial fluid Absorption accelerated by hyaluronic acid

Question 26

Iv

Answer 26

100% bioavailability Offers • immediate response • Titration of effects • ideal in shocked patients

Question 27

Intra-arterial

Answer 27

Not for anaesthesia most drugs cause vasospasm, ischemia and tissue necrosis. Used for targeted chemo

Question 28

Neurexial

Answer 28

• Into Subarachnoid or epidural • Volume of drug determines spread • Concentration determines the intensity • Level of injection determines spread

Question 29

Intraneural

Answer 29

Used in trigeminal neuralgia alcohol directly injected to the gasserian ganglion to destroy it

Question 30

Intrapleural and Intra-arterial

Answer 30

• No systematic absorption • For local pain relief • intrapleural local anesthetic greatly absorbed

Question 31

Novel drug delivery systems

Answer 31

Carbon nanotubules Pockets of drugs and antigen mixture Liposomal suspension of bupivacaine