Patches, injections and inhalers

Question 1

What is transdermal drug delivery?

Answer 1

where the drug is delivered (over time) using a patch on the skin

Question 2

How is TDD achieved? (2 ways)

Answer 2

1. by a matrix e.g. durogesic patches

2. using a rate limiting membrane (reservoir system) e.g. Scopaderm

Question 3

How does the packaging of patches for TDD allow them to work?

Answer 3

• the patch is protected by an occlusive backing layer
• the adhesive creates a diffusion gradient and adheres to the skin
• a removable strip protects the adhesive
• in membrane systems, the membrane will be behind the adhesive layer

Question 4

How are TDD patches packaged?

Answer 4

in a foil lined sachet like pouch for protection

Question 5

In what form will the drug be in in the matrix/reservoir?

Answer 5

-the drug will be in solution/suspension

Question 6

What are the advantages of TDD?

Answer 6

• by passes the GIT
• systemic effects
• no first pass metabolism (goes directly into systemic circulation)
• controlled constant rate of delivery
• long duration of action (up to 7 days)

Question 7

What are the disadvantages of TDD?

Answer 7

• can cause skin irritation
• patch may fall off
• not suitable for all drugs (needs to be hydrophobic)
• not suitable for hairy areas

Question 8

What formulations are injections in?

Answer 8

solutions, suspensions, emulsions

Question 9

What are the different routes for injection?

Answer 9

IM, IV (bolus vs infusion), SC, intradermal, intraarterial, intraspinal

Question 10

If a drug has low solubility, what is it formulated as?

Answer 10

Emulsions

Question 11

Which of IV/IM are o/w and which is w/o?

Answer 11

IV is o/w whereas IM is w/o

Question 12

What other excipients are needed for injection?

Answer 12

1. Water - must be free of pyrogens (harmful bacteria) and be pure
2. Preservatives - to prevent bacterial growth
3. Buffers
4. Tonicity adjusting agents e.g. 0.9% NaCl

Question 13

In order of most to least, which formulations are the most stable?

Answer 13

emulsions — suspensions — solution

Question 14

How are injections packaged?

Answer 14

• If as single dose ampoules, they’re in glass packaging,
• For multi dose vials, they’re in glass with a rubber bung
• Pre-filled syringes are in plastic/glass
• Can be given as infusion bags

Question 15

What are the advantages of injections?

Answer 15

• they can be for local or systemic action
• used when oral route isn’t appropriate
• avoids all problems of the GIT
• no first pass metabolism
• rapid onset of action or prolonged release

Question 16

What are the disadvantages of injections?

Answer 16

• they’re invasive/painful
• patients can be scared of needles
• risk of infection or embolism (block of an artery by a clot)
• difficult to reverse effects
• difficult to administer in some patients

Question 17

How is particle size in inhalers related to drug penetration?

Answer 17

The smaller the particle size, the further down the respiratory tract the drug will penetrate

Question 18

What is optimum particle size in inhalers and what happens above and below this size?

Answer 18

3-5 micrometers is optimum.
When they are less than 1 micrometer, the particles are exhaled and so the drug isn’t retained.
More than 10 micrometers results in particles staying in the oropharynx

Question 19

What is an MDI?

Answer 19

They are aerosols of drugs in solution or suspension which have a propellant such as HFAs or CFCs

Question 20

What does actuation result in in MDIs?

Answer 20

It results in evaporation of propellant to form droplets to be inhaled into the lung

Question 21

What is the technique used by the patient for MDIs?

Answer 21

Coordination is required between actuation and inspiration as well as a long steady inspiration (to avoid exhaling the drug particulates)

Question 22

What item can be used to aid the use of MDIs and how do they work?

Answer 22

Spacers are used to remove the need to coordination. Children are always prescribed a spacer with an MDI

Question 23

What is a breath actuated MDI?

Answer 23

Inhalation triggers the actuation of the device and so this is used for those who have difficulty coordinating. Brands are easi breathe and autohaler
However a strong breath is required to trigger the actuation.

Question 24

What are the excipients for MDI?

Answer 24

• Propellant (HFA and CFC)
• surfactants (to aid wetting for suspension e.g. oleic acid)
• co-solvents (to aid dissolution e.g. ethanol)

Question 25

What is a dry powder inhaler?

Answer 25

This is breath actuated too but the drug is a micronised powder for inhalation. Brands include accuhaler, tubrohaler.
No propellant or coordination are required and larger doses are given.

Question 26

What are the excipients in DPI?

Answer 26

• carrier for the drug e.g. accuhaler, lactose

- pure drug e.g. turbohaler

Question 27

Which is more stable, MDIs or DPI?

Answer 27

MDIs are more stable as the container/packaging protects it from oxidation, hydrolysis and microorganisms. DPI however are susceptible to moisture degradation, therefore are less stable

Question 28

What are the advantages of inhalers?

Answer 28

• can use small doses
• reduced systemic side effects
• fast onset of action
• can use drugs with poor bioavailabilty

Question 29

What are the disadvantages of inhalers?

Answer 29

• difficult technique
• not suitable for all drugs
• only 20% of drug reaches the lung
• inflammation can reduce the size of the airways