Drug Microcapsule and Release Models (G1)

Question 1

What is a microcapsule?

Answer 1

A small capsule of drug, dye or solution coated in a shell rendering them temporarily inactive

Question 2

What are the advantages of microcapsules? (5)

Answer 2

• Controlled drug release (over months) (reduced toxicity and longer therapeutic effect)
• Drug protection
• Can be triggered to release drug by external stimuli
• Less frequent administration required
• Facilitate intracellular delivery
• Can be fabricated using many methods

Question 3

Why might microcapsules be more effective than taking multiple doses (pulsatile dosage)

Answer 3

Microcapsules sometimes need taking monthly and are capable of maintaining a constant concentration of the drug within the therapeutic window. (Zero order delivery)
Pulsatile doses, produces a pulsating drug concentration profile in which the conc constantly dips above the toxic level and below the minimal therapeutic level

Question 4

Why might a pulsating drug concentration profile be bad?

Answer 4

• Dips in and out of therapeutic window
• Side effects are seen when the drug goes into the toxic level

Question 5

What are the starting ingredients in microcapsule production from Emulsion droplets

Answer 5

• the Dispersed Phase: A solution containing the active ingredient, excipient dissolved in solvent
• The Continuous Phase: A liquid that doesn’t mix with the solvent + a surfactant (Stabilises droplet formation)

Question 6

How do we produce microcapsules from emulsion droplets

Answer 6

1) Add the dispersed phase to the continuous phase
2) the 2 immiscible solutions emulsify like oil in water
3) Droplets of API+excipient+Solvent form in the continuous phase
4) In a secondary reaction of solidification (cross-linking and polymerisation), the solvent is boiled off, and the excipient and surfactant react to form a shell around the API creating the micro-capsule

Question 7

What are the 2 types of microcapsules? And what is their difference?

Answer 7

Reservoir and matrix type
- Reservoir: A polymer membrane encapsulates the drug and solute and it diffuses out over time
- Matrix: The drug is dispersed in a solute without a shell like being in an oil droplet in water

Question 8

What are a few potential routes to create microcapsules?

Answer 8

• Water in Oil emulsification
• Oil in water emulsification
• Oil in water in Oil emulsification
• Water in Oil in Water emulsification
• Liposomes
• Polymeric
• Solid lipid
• Hydrogel

Question 9

What does a zero order profile of mass of drug release (y) vs time (x)

Answer 9

Question 10

What would Q0, Qt and K0 represent?

Answer 10

Q0 - Amount of drug initially present
Qt - mass of drug in solution at t time
K0 - Release rate of drug into solution

Question 11

What do these graph show?

Answer 11

both show a first order release kinetics
left: mass of drug left in capsule (log scale)
right: Mass of drug released vs time (zero order)