Modified drug release
- Created by: Labake
- Created on: 27-03-17 16:45
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- Modified Drug release
- For oral dosage
- Limitations to dosing
- Conc of drug in plasma fluctuates after dosage even after steady state
- Forgotten or overnight doses for drugs with short half lives e.g. biological drugs
- Advantages
- Peaks & troughs minimised – steady state therapeutic levels to better manage disease
- Improved Compliance- less frequency doses
- Better safety margin- Lower side effects
- Efficient use of drug – lower overall amount used
- Reduction in healthcare costs- less monitoring, shorter treatment time, less dispensing (single dose).
- Efficient use of drug – lower overall amount used
- Better safety margin- Lower side effects
- Improved Compliance- less frequency doses
- Peaks & troughs minimised – steady state therapeutic levels to better manage disease
- Disadvantages
- Risk of dose dumping (lethal dose)
- Instability of drug, more costly manufacturing process
- Drug delivery systems
- Sustained Action:
- An initial release of drug sufficient to provide a therapeutic dose soon after administration. Then a gradual release over an extended period.
- Prolonged Release:
- Drug absorbed over longer period of time. Onset delayed due to slower release rate from the dosage form.
- Extended Release (ER):
- Releases drug slowly. Plasma conc maintained for long time (usually between 8 and 12 hours)
- Repeat Action:
- 1 dose released soon after admin. Second or third doses are released at later intervals
- First priming doe is rapid
- Layered tablet or tablet within a tablet
- 1 dose released soon after admin. Second or third doses are released at later intervals
- Controlled Release (CR):
- Release drug at a constant rate and provide plasma concentrations that remain invariant with time.
- Delayed Release:
- Drug not released immediately following admin. but at a later time e.g. enteric-coated tablets.
- For site specific absorption
- Drug not released immediately following admin. but at a later time e.g. enteric-coated tablets.
- Sustained Action:
- Controlling rate of release
- 1. Physical barrier
- 2. Chemical barrier
- To keep plasma conc. of drug constant
- OR to keep it declining at VERY slow rate, plasma conc in therapeutic range for long time
- Release rate should equal clearance rate
- Affected by different GI pHs (2 to 8), age, race, disease and food intake
- Use initial priming (loading) dose then add more maintenance doses
- Drugs suitable for MR
- Drugs with biological half life of 2-8hrs
- Below 2 hours= cleared quickly and LARGE dose needed
- High risk of dose dumping
- Above 8hrs= no need for MR as lasts long already
- Below 2 hours= cleared quickly and LARGE dose needed
- Drugs with large theraperutic window
- Log P between 2.2- 3.3
- Permeable and uniformly absorbed in GIT
- Moderate potency that requires small doses
- Very potent drug= dose dumping risk
- PHYSIO-CHEMICAL properties (solubility, stability, pKa)
- Aim for high solubility and high permeability (Class 1)
- Class 2 okay for controlling solubility (low solubility, high permeability)
- Exceptions: Vancomycin- high solubility but low permeability- fine for C.diff or MRSA in gut
- Aim for high solubility and high permeability (Class 1)
- Drugs with biological half life of 2-8hrs
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