Principles of Drug Delivery Flashcards by Brooke Thornburg

Controlled drug delivery types

-temporal
-spatial

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temporal controlled drug delivery

-sustained release (delayed and extended)
-pulsatile release

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spatial controlled drug delivery

-systemic
-local
-targeted

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Potential advantages of controlled release

-maintain good concentrations
-improve efficiency
-minimize side effects
-less freq admin
-inc convenience and compliance

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Disadvantages of controlled release

-high production cost
-leakage of drug mass (dose dumping)
-difficult to stop drug release
-biocompatibility of the delivery systems?
-necessity of surgical operation

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Temporal controlled drug delivery is needed for:

-optimizing concentration
-reduce freq of admin
-simulating multiple dosing via combo of immediate-release + pulsatile delivery system

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Temporal controlled drug delivery is NOT needed for:

-drugs w long half-life
-drugs w undesirable long-term effects
-drugs that need immediate effect

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Drug release control mechanisms

-diffusion-controlled systems
-dissolution-controlled systems
-erosion-controlled systems
-osmotic systems
-swelling systems

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Diffusion-controlled systems

-drug DIFFUSION through polymer network is rate-limiting step

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types of diffusion-controlled systems

-reservoir systems
-matrix systems

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Reservoir systems

-diffusion controlled system
-drug reservoir
-surrounded by release rate controlling membrane

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matrix system

-diffusion controlled system
-drug + matrix former

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Ocusert

-diffusion control reservoir
-pilocarpine reservoir
-rate controlling membranes
-eyeball medication

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Tetracycline periodontal fibers

-diffusion control reservoir
-tetracycline in polymer membrane
-tooth

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Norplant

-diffusion control reservoir
-silicone capsules w levonorgesterel
-injection into forearm

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Examples of diffusion-controlled RESERVOIR systems

-Ocusert
-Periodontal Fibers
-Norplant

Drug release from diffusion reservoir equation

-slide 14

Drug release from diffusion MATRIX

-drug and matric former are not physically separated
-release depends on GEOMETRY

Drug release from MATRIX equation

SLIDE 26

Reservoir vs MATRIX

-drug separated from skin by rate controlling adhesive in reservoir
-in matrix, drug is within adhesive

reservoir vs matrix. math

Nexplanon

-rod
-matrix
-inserted under skin

Dissolution system types

-encapsulated
-matrix

Dissolution matrix math

slide 33

Osmotic systems

-1 chamber or 2 chamber -rigid film coating

Film coating of osmotic systems

-permeable for water -not permeable for drug excipients -rigid to resist hydrostatic pressure = push out drug

Osmotic mech

-overcoat provides immediate release -1 hour later push compartment expands releasing drug from compartment 1 for the rest of the morning -afternoon: push compartment expands and releases drug from compartment 2 during afternoon

Osmotic pump

-agent -osmotic layer -semipermeable membrane -impermeable reservoir -flow moderator

***IF THE DRUG IS ADDITIONALLY RELEASED THRU DIFFUSION

slide 40

slide 41 good

recap

Erosion controlled systems mech

-initial release controlled by diffusion of drug on surface -sustained release determined by erosion of polymer

Types of erosion

-surface erosion (lose from surface) -bulk erosion (lose mass overall)

Examples of erosion-controlled systems

-Zoladex -Lupron -Nutropin -Gliadel Wafer -Sustol

Gliadel Wafer

-short half life -dose limiting sie effect (bone marrow suppression and pulmonary fibrosis) -avoid systemic admin -place into cavity of tumor while cranium still open -no need to remove polymer remains -temporal control: released in a time controlled manner -spatial control: released in direct vicinity of site of action -BCNU -polyanhydride

Lupron Depot

-erosion -PLGA -prostate cancer -injected IM -1-4 month release

PLGA poly(lactic-co-glycolic acids)

-polymer undergoes hydrolysis = releases drug

Sustol sustained release injection

-Erosion -

Swelling Controlled systems

-polymer swelling -dec drug release rate bc of longer diffusion pathway -polymer network size inc = in drug release rate