Oral Drug Delivery Flashcards
What are some disadvantages to oral dose forms
The degradation and metabolism
The onset of action
What are the drug absorption sites for oral drug delivery?
Stomach
Small intestine (major)
There is very limited absorption in the esophagus and the colon
What are some possible influencing factors of the stomach as an absorption site?
pH
Enzymes
Food
Liver metabolism
What are some necessary drug properties for oral administration?
Reasonable absorption profiles (solubility, permeability, irritability)
Acceptable physical, chemicals and biological stability (temperatures, light, moisture, various pH values, enzymes, first pass metabolism)
Good processing characteristics (compatibility with excipients, compactability, compressibility
What are the five major obstacles I oral drug delivery?
Solubility Stability Absorption Metabolism Drug targeting
What are different ways to increase solubility?
Selecting different drug salt forms
Microionizing drug particles
Improving formulation disintegration and dissolution
Incorporating other additives
What are the advantages to oral drug delivery?
Effectiveness
Accuracy
Convenience
Economy
What are some ways to improve stability?
Coating
Additive addition
Packaging protection
Controlled release formulation
How can absorption extent be improved
Selecting the appropriate active and inactive ingredients
Increasing drug disintegration and dissolution rate
Preventing drug compounds from decomposition
Administration approaches (administer with/without food and/or water)
How can we prevent metabolism before absorption?
Structure modifications
Coating
Controlled release
How can we prevent metabolism after absorption?
Pro drugs
What are some special delivery systems that may help with drug targeting?
Micro capsules
Liposomes
Nanoparticles
But these systems are better IV
What is sustained release?
Sustained release constitutes any dodge form that provides medication over an extended period of time
What is controlled release?
Controlled release denotes that the system is able to provide some actual therapeutic control (I.e., controlling drug concentrations in the target site)
What are some characteristics unique to controlled release dosage forms?
Enables the patient to take less amount of drug with fewer administration frequencies (minimizes adverse effects and accumulation)
Enhance therapeutic outcome by modifying drug release rate, reducing drug concentration fluctuations and improving drug bioavailability
Patient compliance
The average cost of treatment over an extended time period is reduced (sometimes)
More stringent quality control
What should the half life of a controlled release drug be?
2-8 hours
How quickly should the drug be absorbed?
Within 3-4 hours (faster than the rate of drug release)
What is the optimal drug dose for controlled release formulations
Maximum of 0.5-1g
The mechanisms by which drug is released from controlled release products is:
Diffusion
Dissolution
Combination diffusion and dissolution
Osmotic pressure
What are the 3 systems of controlled release?
Reservoir system Matrix system Bioerodible system Dissolution-controlled systems Osmotic pumps
Describe the reservoir system
This type of controlled release formulation is characterized by a core of drug (drug reservoir) surrounded by a polymeric membrane
Dissolution medium has to diffuse across the membrane to dissolve the drug, which will then diffuse through the membrane too deliver the drug content
Describe matrix systems
Matrix systems consist of drug dispersed homogeneously throughout a polymer matrix
Describe bioerodible systems
Bioerodible systems are made of drug components homogenously dispersed in chemical polymers (the polymers are water-soluble, so drug ingredients and matrix polymers dissolve and release at the same time)
How can drug release be controlled by pure dissolution mechanism?
By decreasing dissolution rate of the active ingredients. This is achieved by:
- selecting appropriate salts or derivatives with lower solubility,
- coating the drug with slowly dissolving material, or,
- incorporating it into a tablet with a slowly dissolving carrier
Describe osmotic pumps
Osmotic pumps rely on osmotic pressure as the driving force to control drug release form the systems.
Drug cores consist of a mixture of active ingredient and osmotic-pressure producing agents
How are osmotic pumps manufactured?
The cores are coated with a semi-permeable polymer and an orifice is drilled on the surface of the coating by a laser beam
After in contact with the dissolution medium, water will penetrate into the core and dissolve the components, the osmotic pressure produced will then drive the drug out of the membrane through the small orifice
