30 Questions
What is the primary advantage of administering oral medicines?
Improved patient compliance
Why is drug level in the blood easier to control with IV infusion compared to oral administration?
Immediate availability of the drug to the system
What is a common limitation associated with conventional immediate-release oral dosage forms?
Frequent dosing intervals
Which characteristic is NOT a limitation of conventional oral dosage forms?
Higher patient compliance
Why are more than 70% of all medicines delivered by the oral route?
Improved patient compliance
What is the main goal of modified-release oral dosage forms?
To maintain therapeutic drug concentrations over an extended period
What is a common formulation technique used in sustained-release drug formulations?
Embedding the drug in wax or plastic matrix
How long can solution and pellets (7 mm) stay in the stomach if taken with a heavy meal?
Up to 10 hours
Which physicochemical property of a drug influences the design of oral modified-release delivery systems?
Stability
What is the purpose of using coatings in sustained-release formulations?
To provide slow release of maintenance dose
Which formulation method involves microencapsulation in sustained-release drug delivery?
Microencapsulation
What is a factor that influences the design strategy of oral modified-release drug delivery?
Physiology of the gastrointestinal tract and drug absorption
What is a key characteristic of drugs that are ideal candidates for extended-release formulations?
They are administered in relatively small doses.
Why are drugs with long half-lives considered long-acting?
Because they exert therapeutic activity for an extended period.
Why are drugs with very short half-lives not ideal for extended-release formulations?
They require high amounts (dose).
Why are drugs with narrow therapeutic indices poor candidates for extended-release formulations?
Due to technological limitations of precise control over release rates.
Which type of drugs would be difficult to formulate as oral extended-release dosage forms?
Drugs that require large amounts for efficacy.
What distinguishes an ideal drug candidate for extended-release formulations from conventional ones?
They exhibit either very slow or very fast rates of absorption.
What initiates drug diffusion and release in a membrane-controlled system?
Water in
Which component is essential in a single unit membrane-controlled drug delivery system to allow water penetration and drug dissolution?
Filler
What can happen if an inappropriate soluble filler is used in a membrane-controlled system?
Increased internal osmotic pressure followed by membrane rupture
Which of the following is NOT a suitable diluent (filler) for a single unit membrane-controlled drug delivery system core formulation?
Glycerin
What governs the choice of solubilizer in a membrane-controlled drug delivery system?
Solubility characteristics of the drug
Why should an extended-release tablet core in a single unit membrane-controlled system not disintegrate?
To allow drug dissolution for diffusion through the membrane
What is the primary purpose of using multiple unit systems in drug delivery?
To optimize release for individual drugs
Which polymer is commonly used as a release-controlling membrane in membrane-controlled drug delivery systems?
Acrylic polymers like Eudragit RL
What is the importance of ensuring the membrane in a drug delivery system remains intact?
To prevent film failure issues
Which approach is preferred when a high drug loading is required in multiple unit systems?
Formulation of small spheroids using an extrusion spheronization process
What are typical release modifiers used in membrane-controlled drug delivery systems?
Polyethylene glycols and propylene glycol
Why are multiple unit membrane-controlled systems less likely to suffer from film failure issues?
Because they allow optimization of release for individual drugs
Study Notes
Formulation Methods for Sustained Drug Release
- Chemical or physical barriers are used to provide slow release of maintenance dose in SR formulations.
- Techniques used to build barriers include:
- Coatings
- Embedding the drug in wax or plastic matrix
- Microencapsulation
- Chemical binding to ion-exchange resins
- Incorporation into an osmotic pump
Design of Oral Modified-Release Drug Delivery
- Factors influencing design strategy include physiology of the gastrointestinal tract and drug absorption.
- Solution and pellets can stay in the stomach for up to 10 hours if taken with a heavy meal.
- Transit time through the small intestine is approximately 3 hours.
Physicochemical Properties of Drug
- Aqueous solubility and stability
- pKa
- Partition coefficient
- Salt form
Ideal Properties of Drug Candidates
- Exhibit neither very slow nor very fast rates of absorption and excretion (half-life between 2 and 6 hours).
- Uniformly absorbed from the GI tract.
- Administered in relatively small doses (not exceeding 125-325 mg).
- Possess a good margin of safety.
- Used in treatment of chronic rather than acute conditions.
Membrane-Controlled Drug Delivery Systems
- Single unit systems: essentially a tablet formulation, but with differences from conventional dosage forms.
- Core formulation: suitable diluents include lactose, microcrystalline cellulose, dextrose, sucrose, and polyols.
- Solubilizer choice is governed by the solubility characteristics of the drug.
- Satisfactory lubricant and glidant are required.
Multiple Unit Systems
- Comprise of more than one discrete unit.
- Typically coated spheroids (pellets approximately 1 mm) in diameter filled into hard gelatin capsule shell.
- Manufacturing approaches: using inert sugar spheres coated first with drug and then with the release controlling membrane, or formulation of small spheroids containing the drug using an extrusion spheronization process.
Release Controlling Membrane
- Must be intact during the period of release.
- Typical polymers used include ethyl cellulose, acrylic polymers, polyvinylacetate, silicone elastomers.
- Release modifiers: polyethylene glycols, propylene glycol, or other polyols and water-soluble polymers.
Advantages of Multiple Unit Membrane-Controlled Systems
- Allow release to be optimized for individual drugs in a system delivering two or more active drugs.
- Less likely to suffer from problems associated with film failure.
Explore concepts related to modified-release oral drug delivery and the ideal drug concentration at the site of action. Learn about controlling drug levels in the blood and monitoring drug effects through IV infusion.
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