Drug Delivery Systems

Question 1

How can a drug delivery system be formulated?

Answer 1

• to allow selective targeting of a tissue site
• to avoid pre- or systemic metabolism
• to allow a 24 hour action

Question 2

What determines the drug delivery system we use?

Answer 2

• the dose of the drug to be given
• the frequency of administration
• the timing of administration

Question 3

What must be considered when choosing a dosage regime?

Answer 3

• recommended dose
• renal function
• hepatic function
• age and weight
• disease
• drug toxicity
• starting dose

Question 4

What is considered oral medication?

Answer 4

• solutions
• suspensions
• capsules
• tablets
• modified release tablets

Question 5

How are oral medications absorbed?

Answer 5

via the GI tract

Question 6

How can oral medication be administered?

Answer 6

• buccal
• sublingual
• oral
• rectal

Question 7

What are solutions and suspensions useful for?

Answer 7

• young
• old
• patients with swallowing difficulties

Question 8

How can solutions and suspensions also be given?

Answer 8

Via a naso-gastric or PEG tube

Question 9

Describe the absorption of solutions/suspensions given via ng/PEG tube.

Answer 9

• absorbed extremely rapidly

- most rapidly from the small intestine

Question 10

What is absorption of solutions/suspensions dependent on?

Answer 10

Gastric emptying

Question 11

What is a suspension?

Answer 11

Dispersions of coarse drug particles in a liquid phase which can be contained within a small volume

Question 12

What are suspensions good for?

Answer 12

drugs which are insoluble unpalatable as they are better tolerated

Question 13

What do oral delivery systems involve?

Answer 13

Use of various polymers and hydrogel based formulations

Question 14

What is the rate limiting step in absorption of tablets?

Answer 14

Dissolution or tablet break down

Question 15

What are the distinct advantages of tablets/capsules?

Answer 15

• convenience
• accuracy of dose
• reproducibility
• drug stability
• ease of mass production

Question 16

What does enteric coating on a tablet do?

Answer 16

enteric coating delays disintegration of the tablet until it reaches the small intestine

Question 17

Why are tablets enteric coated?

Answer 17

• protect the drug from stomach acid i.e. omeprazole

- protect the stomach from the drug i.e. aspirin

Question 18

Why are prolonged/ delayed release formulations useful? (5)

Answer 18

• most disorders required prolonged therapy
• maintains drug levels within a therapeutic range
• reduces the need for frequent dosing
• compliance is improved
• improved nursing and doctor compliance

Question 19

How can the time course for a drug in the body be prolonged?

Answer 19

• reducing the rate of drug absorption

- giving the drug in a form which has slower, but sustained release

Question 20

What are oral examples of prolonged/delayed release drugs?

Answer 20

• verapamil
• diltiazem
• isosorbide mononitrate
• lithium
• carbamazepine

Question 21

What are parenteral preparation examples of prolonged/delayed release drugs?

Answer 21

• IM injections
• flupenthixol
• risperidone

Question 22

What are surgical implant examples of prolonged/delayed release drugs?

Answer 22

• progesterone contraception

- testosterone

Question 23

What are prodrugs?

Answer 23

Prodrugs are synthesised inactive derivatives of an active drug which requires to be metabolically activated after administration

Question 24

What are the advantages of using prodrugs?

Answer 24

• prolongation of duration of action

- avoidance of degradation of the drug in the gut

Question 25

What is buccal/sublingual administration ideal for?

Answer 25

drugs which have extensive pre-systemic or first pass metabolism

Question 26

Why might a drug be administered rectally?

Answer 26

- to treat local conditions such as proctitis | - to achieve systemic absorption (indomethacin)

Question 27

Does administration via the rectal route bypass pre-systemic metabolism?

Answer 27

yes

Question 28

What can be administered vaginally?

Answer 28

- pessaries | - creams

Question 29

What does the injection based drug delivery system provide?

Answer 29

fast systemic effects bypassing first-pass metabolism

Question 30

When are drugs administered IV?

Answer 30

- a rapid onset of action is required - careful control of plasma levels is required - a drug has a short half life

Question 31

IV formulations may be given...

Answer 31

- rapidly - slowly to prevent toxic effects - continuous infusion to ensure accurate control of blood levels especially when a drug has a narrow therapeutic index

Question 32

What do IM injections allow?

Answer 32

a more sustained duration of action

Question 33

What are subcutaneous injections used for?

Answer 33

- insulin - heparin - narcotic analgesics

Question 34

How does the transdermal drug delivery system work?

Answer 34

- The drug crosses the skin surface by diffusion by percutaneous absorption and goes into systemic circulation - bypasses first-pass haptic inactivation

Question 35

What do skin patches allow?

Answer 35

The release of a drug from reservoir into the skin and then into the systemic circulation.

Question 36

How can inhaled drugs be delivered?

Answer 36

- pressurised aerosol - breath actuated aerosol - nebuliser - dry powder device

Question 37

What are the advantages of inhalation?

Answer 37

- drug delivered directly to site of action - rapid effect - small doses used - little systemic absorption - reduced adverse effects

Question 38

What is the major disadvantage of inhalation?

Answer 38

Patient education is essential

Question 39

Describe the action of monoclonal antibodies.

Answer 39

mAbs act directly when binding to a cancer specific antigen and induce immunological response to cancer cells

Question 40

Why have mAbs been modified?

Answer 40

For delivery of a toxin, cytokine or other active drug

Question 41

What do pre-clinical and clinical liposomal packed drugs exhibit?

Answer 41

reduced toxicities with enhanced efficiency

Question 42

What does nanotechnology allow in drug delivery systems?

Answer 42

The drug can be targeted to a precise location which would make the drug much more effective and reduce the chance of possible side-effects

Question 43

Name 3 nanocarriers?

Answer 43

- nanoparticles - nantubule - nanoshell

Question 44

What are the advantages of nanoparticle based drug delivery?

Answer 44

- more specific targeting and delivery | - reduction in toxicity while maintaining therapeutic efficiency

Question 45

What are nanoerythrosomes?

Answer 45

- Resealed erythrocytes that can carry proteins, enzymes and macromolecules - Used in the treatment of liver tumour, parasitic disease and enzyme disease

Question 46

What is genetic transfer system in clinical trials for?

Answer 46

- adenovirus | - HIV