Drug Delivery - MR Systems (Cases)

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  • Created by: LBCW0502
  • Created on: 23-11-19 11:40
Describe features of gastroretentive technologies
Standard CR dosage forms offer only limited advantage for drugs that have an absorption window in the upper SI (target absorption area). Design systems which stay longer in the stomach, promote absorption, slow release in the stomach to the SI
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Describe features of gastric emptying (1)
Phase I (basal phase, rare contractions). Phase II (preburst phase, intermittent contractions). Phase III (burst phase, housekeeper waves, undigested material is swept out of the stomach). Phase IV (transition period for next cycle)
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Describe features of gastric emptying (2)
Each cycle lasts 90-120 minutes and is interrupted by ingestion of food (450 kcal)
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What are the parameters that affect gastric emptying? (1)
Density, size and shape of device. Concomitant ingestion of food and its nature, caloric content and frequency of intake. Simultaneous administration of drugs with impact on GIT as anticholinergic agents, opiates, or prokinetic agents
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What are the parameters that affect gastric emptying? (2)
Biological factors such as gender, posture, age, sleep, BMI, physical activity and disease states. Use of passage delaying excipients (triethanolamine myristate). Almost everything seems to affect GE (size, shape, density, food)
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What are the four types of gastro-retention strategies?
Floating devices, expanded devices, high density devices and mucoadhesive systems. Actions in the stomach (delay in the stomach allows for better release of the drug in SI, CR in the stomach, drugs survive in environment of the stomach)
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What is a high density system?
Certain density to reach bottom of stomach, drug release
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What is a floating system?
Intra-gastric floating system with a density of less than 1. Highly dependent on fasted/fed state. Amount, nature, caloric content and frequency of feeding are significant
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What are the types of floating systems? (1)
Raft forming systems (gel forming solution swells, form viscous cohesive gel containing entrapped CO2 bubbles on contact with gastric fluid). Hydrodynamically balanced systems (single unit dosage form contains one or more gel, hydrophilic polymer)
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What are the types of floating systems? (2)
Gas generating systems (float-ability is achieved by generation of gas bubbles). Low density systems (avoid lag time)
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Give an example of a raft forming system
Gaviscon (sodium alginate, aids with digestion) - layer formed over stomach acid, slow release of drug
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Describe features of the hydrodynamically balanced system
Gelatinous barrier, drug diffusion, density <1 inside formulation (float), gel barrier erodes (water uptake), polymer swells, drug is released
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Describe features of the gas generating systems (1)
Sodium bicarbonate used in effervescent tablets, generation of carbon dioxide (bubbles), density of system becomes low (floats), use hydrophilic polymers used for gas generation, drug released at certain rate
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Describe features of the gas generating systems (2)
Carbon dioxide forms a balloon, drug release through semi-permeable membrane
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State features of the low density systems
Microballoons, float in the stomach, drug release
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Describe features of the dome matrix
Composed of two polymeric components, tablet within polymers, dome has gas, formulation floats, membrane permeable to water, water enters to dissolve drug, drug released into solution, supply of drug in SI (constant)
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Describe features of expanding systems (1)
Has to be bigger than the pyloric sphincter (>15 mm). Must be small enough to be swallowed and must not cause gastric obstruction either singly or by accumulation
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Describe features of expanding systems (2)
3 consecutive configurations - small for oral intake, expanded gastroretentive form and final small form that enables evacuation
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Describe features of expanding systems (3)
Small when administered but become larger when in the stomach (expansion, absorption of water), cannot move past pyloric sphincter (must be small enough to swallow, should not cause gastric obstruction)
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Describe features of expanding systems (4)
E.g. 4 lobed, disc, 4-limbed cross, ring, tetrahedron. E.g. oral antiretrovirals (HIV) gastro-retentive, several drugs in one compound, each with specific drug release, collagen dosage form with opaque hard gelatin capsule, GLUTMETZA
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Describe features of super-porous hydrogels
Small when dry, super-absorbance of water causes expansion, remain in stomach for certain period of time (disadvantage – no mechanism of degradation in the stomach after a certain time, risk of gastric obstruction)
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What is sonophoresis?
Improvement of permeation/transport of drugs using ultrasound, ultrasound transducer connected to power supply, waves permeate tissue, bubbles in open pores, drugs permeated, e.g. use to pass drugs through BBB (micro-bubbles). Sonopill (clinic)
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What is iontophoresis?
Electrical current, active/indifferent electrode, drugs permeate membrane (repulsion), improves drug transport, CR (can stop current/stop CR of drug), electrode produces current to push counterion through skin
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State features of applied formulation
Use of microneedles, inject drugs into SI, small micro sized drugs, needles are biodegradable, control release of system
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State features of implantable BioMEMS drug delivery systems (1)
Array of 100s of reservoirs on a dime sized chip. Multiple chemicals stored in their most stable form (e.g. solid, liquid, gel). Microprocessor, wireless or biosensor based control. Local delivery of drugs. High reliability (no moving parts)
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State features of implantable BioMEMS drug delivery systems (2)
Micro-chip implanted. Digitised CR. Drug reservoir, microchip, sealing layer, reservoir caps. Experimental protocol (implant in rats, release radioactive mannitol, collect urine, analysis for radioactive content, indicator of mannitol release)
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Other cards in this set

Card 2

Front

Describe features of gastric emptying (1)

Back

Phase I (basal phase, rare contractions). Phase II (preburst phase, intermittent contractions). Phase III (burst phase, housekeeper waves, undigested material is swept out of the stomach). Phase IV (transition period for next cycle)

Card 3

Front

Describe features of gastric emptying (2)

Back

Preview of the front of card 3

Card 4

Front

What are the parameters that affect gastric emptying? (1)

Back

Preview of the front of card 4

Card 5

Front

What are the parameters that affect gastric emptying? (2)

Back

Preview of the front of card 5
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