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Questions and Answers
What is the main objective of any drug delivery system?
What is the main objective of any drug delivery system?
Ensure safety and improve efficacy of drugs as well as patient compliance.
Which of the following is a type of modified release system?
Which of the following is a type of modified release system?
Modified release dosage forms are not suitable for drugs with a narrow therapeutic index.
Modified release dosage forms are not suitable for drugs with a narrow therapeutic index.
True
What is zero order release?
What is zero order release?
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The technique that involves coating drug particles with polymers is called ______.
The technique that involves coating drug particles with polymers is called ______.
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Name one advantage of modified release dosage forms.
Name one advantage of modified release dosage forms.
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Match the following drug delivery systems to their characteristics:
Match the following drug delivery systems to their characteristics:
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Sustained release dosage forms maintain constant blood levels.
Sustained release dosage forms maintain constant blood levels.
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What kind of drug is not suitable for sustained release formulation?
What kind of drug is not suitable for sustained release formulation?
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What is the Higuchi equation used for?
What is the Higuchi equation used for?
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What does 'dose dumping' refer to?
What does 'dose dumping' refer to?
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Study Notes
Course Overview
- Focuses on principles of pharmaceutical formulation and dosage form design.
- Covers advanced granulation technology and formulation techniques.
- Includes study of polymers used in drug delivery systems and novel drug delivery systems (DDS).
Novel Drug Delivery Systems (DDS)
- Features sustained release concepts and multiple dosing.
- Discusses matrix tablets and controlled-release technology.
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Microencapsulation Techniques:
- Coacervation
- Solvent evaporation
- Interfacial polymerization
- Spray drying
Learning Objectives
- Understand modified release dosage forms and their significance.
- Elaborate on the development of sustained release formulations.
- Describe zero order release kinetics and the mechanisms behind sustained release products.
- Recognize factors influencing sustained release formulation and evaluation.
Rationale for Modified Release Systems
- Objectives include drug safety, efficacy, and patient compliance through controlled plasma drug levels.
- Modified release dosage forms help maintain therapeutic drug levels, reducing dosing frequency.
- Traditional dosage forms often result in fluctuating drug levels requiring frequent administration.
Classification of Modified Release Systems
- Delayed Release Systems: Use intermittent dosing to avoid producing or maintaining constant blood levels.
- Extended Release Systems: Reduce dosing frequency by at least half.
- Orally Disintegrating Tablets (ODT): Rapidly disintegrate in saliva post-administration.
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Sustained Release Systems: Slowly release drug over an extended period.
- Subcategories include controlled release and prolonged release.
- Site Specific and Receptor Release: Target specific organs or tissues, enhancing treatment efficacy.
- Repeat Action: Contain two doses (immediate and delayed release).
Advantages of Modified Release Dosage Forms
- Enhance patient compliance.
- Improve drug utilization by minimizing side effects and drug accumulation.
- Allow for quicker and more efficient treatment delivery.
- Enhance bioavailability of certain drugs and provide significant therapeutic effects.
Limitations of Modified Release Systems
- Not suitable for drugs with narrow therapeutic indices, irregular absorption, or certain absorption behavior.
- Difficult to provide antidotes for sustained release formulations.
- Complex dosage forms can complicate patient management.
Sustained Release Dosage Form (SRDF)
- Designed for prolonged therapeutic effect with terms like prolonged action and controlled release describing functionality.
- Aim for zero order release, but often release mimics zero order in a slow first-order fashion.
Types of Sustained Release Systems
- Dissolution Controlled: Suitable for drugs with slow solubility; uses coatings and matrix systems to control release.
- Diffusion Controlled: Governed by the diffusion of dissolved drugs through membranes or matrixes.
- Reservoir Systems: Feature a semi-permeable membrane controlling drug release via osmotic pressure.
- Ion Exchange Resins: Control delivery of ionic drugs by interacting with ions in the gastrointestinal tract.
Evaluation of Drug Release
- In Vitro Evaluation: Involves measuring dissolution time using rotating paddle or basket methods, ensuring the drug release meets specified criteria.
- Model Dependent Methods: Utilize various kinetic models for analyzing release profiles, such as zero-order and first-order kinetics.
- Model Independent Methods: Assess similarity and difference between drug release profiles using factors like similarity factor (f2) and difference factor (f1).
Recommended Books
- "Pharmaceutics: Science of Dosage Form Design" by M.E. Aulton.
- "Modern Pharmaceutics" by Banker.
- "Pharmaceutical Dosage Forms in Drug Delivery Systems" by Ansel.
- "Theory and Practice of Industrial Pharmacy" by Lachman.### In Vivo Evaluation
- Preliminary in vivo testing involves a limited number of carefully selected subjects with similar characteristics such as body weight, occupation, diet, activity, and sex.
- A single dose is administered, and a 24-hour measurement profile is established.
- Testing can be blind or employ a crossover design.
- Key parameters evaluated include pharmacokinetic profiles, bioavailability data, comparison to reference dosage forms, and reproducibility of in vivo performance.
Kinetics of Drug Release
- Drug release from conventional dosage forms is governed by first-order kinetics, where the release rate decreases exponentially over time.
- Extended-release dosage forms follow zero-order kinetics, meaning the release rate remains constant irrespective of the remaining drug amount.
- Zero-order systems ensure a stable drug concentration, minimizing side effects from peak concentrations and avoiding sub-therapeutic trough levels.
Zero-Order Release Characteristics
- Drug release patterns from zero-order systems are unaffected by the magnitude of the maintenance dose and stable throughout the effective maintenance period.
- Intravenous infusions serve as prime examples of zero-order delivery systems.
- Stability in concentration levels achieved by zero-order systems contributes to effectiveness and reduces toxicity risks.
Factors Influencing Sustained Release (SR) Dosage Form Design
Biological Factors
- Half-Life: Ideal candidates for SR preparation typically have a half-life between 2-8 hours; drugs outside this range may not be suitable.
- Absorption: Drugs with poor absorption rates are less favorable for SR formulations. Specific absorption sites must align with SR release profiles.
- Metabolism: Drugs extensively metabolized in the intestine may not be suitable for SR, as they could be rapidly converted to metabolites before delivery.
Physico-Chemical Factors
- Dose Size: Large dose sizes are incompatible with SR formulations; typical immediate-release doses range from 0.5 to 1 gram.
- Ionization, pKa, and Solubility: Drugs in uncharged forms permeate lipid membranes more easily; very low solubility compounds can be sustained-release candidates.
- Partition Coefficient: High partition coefficients indicate longer retention in the body; lipid-soluble compounds tend to stay longer.
- Stability: Unstable drugs may degrade in the gastrointestinal tract; effective SR systems protect these drugs until they reach stable absorption sites.
Noteworthy Considerations
- Drugs with half-lives shorter than 2 hours or longer than 8 hours are generally excluded from SR formulation.
- Gastric floating systems can enhance retention and absorption for drugs with limited GI activity, while bioadhesive and penetration enhancer strategies may introduce toxicity risks.
- Developing true sustained release systems requires understanding and addressing fluctuating drug concentrations and maintaining therapeutic efficacy throughout treatment durations.
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Description
This quiz covers the principles of pharmaceutical formulation and dosage form design, advanced granulation technology, and novel drug delivery systems including sustained release and polymers used in drug delivery.
