Principles of Drug Delivery Flashcards
Controlled drug delivery types
-temporal
-spatial
temporal controlled drug delivery
-sustained release (delayed and extended)
-pulsatile release
spatial controlled drug delivery
-systemic
-local
-targeted
Potential advantages of controlled release
-maintain good concentrations
-improve efficiency
-minimize side effects
-less freq admin
-inc convenience and compliance
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
Temporal controlled drug delivery is needed for:
-optimizing concentration
-reduce freq of admin
-simulating multiple dosing via combo of immediate-release + pulsatile delivery system
Temporal controlled drug delivery is NOT needed for:
-drugs w long half-life
-drugs w undesirable long-term effects
-drugs that need immediate effect
Drug release control mechanisms
-diffusion-controlled systems
-dissolution-controlled systems
-erosion-controlled systems
-osmotic systems
-swelling systems
Diffusion-controlled systems
-drug DIFFUSION through polymer network is rate-limiting step
types of diffusion-controlled systems
-reservoir systems
-matrix systems
Reservoir systems
-diffusion controlled system
-drug reservoir
-surrounded by release rate controlling membrane
matrix system
-diffusion controlled system
-drug + matrix former
Ocusert
-diffusion control reservoir
-pilocarpine reservoir
-rate controlling membranes
-eyeball medication
Tetracycline periodontal fibers
-diffusion control reservoir
-tetracycline in polymer membrane
-tooth
Norplant
-diffusion control reservoir
-silicone capsules w levonorgesterel
-injection into forearm
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
ri
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
Swelling Controlled systems
-polymer swelling
-dec drug release rate bc of longer diffusion pathway
-polymer network size inc = in drug release rate
