Drug Delivery Systems Overview

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Questions and Answers

What is a primary goal of developing sustained release drug delivery systems (SR DDS)?

To extend the duration of action of the drug (correct)

To enhance the fluctuations in plasma levels

To increase the frequency of dosing

To decrease patient compliance

Which of the following is a disadvantage of sustained/controlled release dosage forms?

Possibility of dose dumping (correct)

Enhanced patient compliance

Predictable in vitro/in vivo correlation

Reduced potential for fluctuation in drug levels

What is the purpose of timed release drug delivery systems?

To provide immediate drug release

To increase drug utilization in the stomach

To achieve drug release after a specific lag time (correct)

To reduce the onset of drug action

Which of the following statements about zero-order release is true?

It maintains a relatively constant drug level in the body Signup and view all the answers

What is a potential benefit of using sustained release dosage forms?

More uniform effects of the drug Signup and view all the answers

What is the primary purpose of drug delivery systems?

To package drugs for optimal delivery. Signup and view all the answers

Which of the following is a characteristic of conventional drug delivery systems?

Offers rapid onset of action. Signup and view all the answers

What is one limitation of conventional drug delivery systems?

They offer poor control over drug release profiles. Signup and view all the answers

Novel drug delivery systems are primarily researched to improve which aspect of drug action?

Drug efficacy and safety. Signup and view all the answers

Which term describes drug delivery at a predetermined rate for a specific time period?

Rate controlled delivery. Signup and view all the answers

Sustained drug delivery aims to achieve which of the following?

Continuous supply of drug over time. Signup and view all the answers

What does targeted drug delivery primarily focus on?

Delivering drugs to specific sites in the body. Signup and view all the answers

Which of the following is NOT a type of novel drug delivery system?

Oral tablets. Signup and view all the answers

What equation is used to calculate the rate of drug released (dm/dt)?

dm/dt = ADK ΔC/L Signup and view all the answers

What is a potential risk associated with reservoir devices if the membrane ruptures?

Drug dumping into the bloodstream Signup and view all the answers

Which characteristic does NOT influence the rate of drug release in reservoir devices?

Water solubility of the drug Signup and view all the answers

What is true about matrix devices in drug delivery systems?

They are easier to produce than reservoir or encapsulated devices. Signup and view all the answers

What factors determine the rate of drug release from a matrix device?

Rate of drug diffusion and polymer thickness Signup and view all the answers

Which of the following is an advantage of using a reservoir type drug delivery system?

Release rates can be varied with the polymer type Signup and view all the answers

What are commonly used polymers in reservoir devices?

Poly-vinyl acetate and hydrogel Signup and view all the answers

Which statement accurately describes drug release in matrix devices?

Drug release depends on the dissolution of the outer matrix layer. Signup and view all the answers

What is a potential drawback of fracture in drug implantation systems?

It can result in dose dumping. Signup and view all the answers

What environmental condition prompts swelling-controlled release systems to expand?

Absorption of water or body fluids Signup and view all the answers

What advantage does hydroxypropyl methylcellulose (HPMC) provide in drug release formulations?

It forms a viscous gel to control drug release. Signup and view all the answers

Which of the following combinations may delay drug release rates when using HPMC?

HPMC and ethyl cellulose Signup and view all the answers

What is a critical function of swelling in swelling-controlled drug release systems?

To allow drug diffusion through the polymer network. Signup and view all the answers

What is a requirement for removing implanted drug delivery systems?

They must be physically removed from implant sites. Signup and view all the answers

What characteristic of HPMC enables customization of drug release profiles?

Variability in methoxyl and hydroxypropyl substitutions Signup and view all the answers

When considering drug stability in delivery systems, what is an essential factor?

Potential toxicity if the system fails Signup and view all the answers

What is a major advantage of erodible systems regarding polymer removal?

Polymers do not need to be removed from the body after drug supply is exhausted. Signup and view all the answers

How does hydrolysis contribute to bulk erosion in polymers?

It degrades large polymers into smaller biocompatible compounds. Signup and view all the answers

Which of the following factors does NOT affect the degradation of polymers?

Color of the polymer Signup and view all the answers

What characteristic is common among synthetic biodegradable polymers utilized for drug delivery?

Flexibility to yield multiple release profiles Signup and view all the answers

Which process occurs during surface erosion of polymers?

Degradation only takes place at the surface of the polymer. Signup and view all the answers

Which polymer is NOT mentioned as a common synthetic biodegradable polymer for drug delivery?

Polyvinyl chloride Signup and view all the answers

What is a key reason for the use of polyesters in drug delivery systems?

They are biocompatible and biodegradable. Signup and view all the answers

Which of the following drugs is not listed as being delivered using polyester-based systems?

Antibiotics Signup and view all the answers

Study Notes

Introduction

Drug delivery systems encapsulate drugs in nanoparticles such as micelles, liposomes, nanocapsules, nanospheres, and others.
This encapsulation improves therapeutic index and reduces adverse side effects.

Classification of drug delivery systems

Drug delivery systems (DDSs) are divided into two main types:
- Conventional DDSs / immediate release formulations
- Novel drug delivery systems (NDDS)

Conventional DDSs

These systems provide rapid onset of action for some drugs like analgesics, antipyretics, and vasodilators.
Includes simple methods like oral, topical, inhaled, or injection.

Limitations of conventional DDSs

Rapid drug elimination leading to frequent dosing
Fluctuations in plasma drug levels resulting in adverse effects
Inability to target specific sites in the body

Novel Drug Delivery Systems (NDDS)

Focus on controlling pharmacokinetics (ADME), pharmacodynamics, non-specific toxicity, immunogenicity, and drug efficacy.
Address drug delivery complications that conventional systems cannot minimize.
Often called "controlled DDS" and use advanced techniques and new dosage forms.

Terminology

Rate controlled delivery: Delivers drugs at a predetermined rate systemically or locally for a specified period.
Sustained/prolonged/extended drug delivery: Releases drugs slowly and provides a continuous supply over a prolonged period.
Targeted drug delivery: Delivers drugs to specific sites in the body.
Zero-order release: Drug release does not vary with time, maintaining a relatively constant level in the body for longer periods.
Timed (delayed) release DDS: Releases drugs after a lag time of 4-5 hours.
Enteric coated dosage: Designed to protect the drug in the stomach and release it in the colon.

Rationale for Developing SR DDS

Extends the duration of drug action.
Reduces dosing frequency.
Minimizes plasma level fluctuations.
Improves drug utilization.
Minimizes adverse effects.
Improves patient compliance.

Conventional vs Controlled Release DDS

Conventional Release:
- Frequent dosing (rapid elimination)
- Fluctuation in plasma levels
- Limited targeting
Controlled Release:
- Reduced dosing frequency
- Stable plasma levels
- Targeted delivery

Advantages of Sustained/Controlled Release Dosage Forms

Reduced drug administration frequency.
Reduced plasma level fluctuations.
Avoidance of night-time dosing.
Increased patient compliance.
More uniform effect.

Disadvantages of Sustained/Controlled Release Dosage Forms

Unpredictable or poor in vitro/in vivo correlation.
Reduced potential for dose adjustment.
Possibility of dose dumping (sudden release of a large amount of drug).
Delay in onset of drug action.
Poor systemic availability in general.

Fick's first law of diffusion

Calculates the rate of drug released (dm/dt).
Formula: dm/dt = ADK ΔC/L
- A = Area
- D = Diffusion coefficient
- K = Partition coefficient
- L = Diffusion path length
- ΔC = Concentration difference across the membrane.

Diffusion-Controlled Systems

Reservoir device: Drug is contained in a core reservoir covered by a thin polymeric membrane.
- Release is by diffusion through the membrane.
- Rate is governed by membrane thickness, porosity, and drug characteristics.
- Risk of dose dumping if the membrane ruptures.
- Difficult for high molecular weight compounds.
Matrix device: Drug is dispersed throughout a polymer matrix.
- Release depends on the rate of drug diffusion.
- Easier to produce than reservoir devices.
- Can deliver high molecular weight compounds.

Difference between Reservoir and Matrix Systems

Reservoir:
- Advantages: Zero-order delivery, variable release rates.
- Disadvantages: Dose dumping risk, removal required for implants, difficult for high molecular weight.
Matrix:
- Advantages: Easier to produce, high molecular weight delivery.
- Disadvantages: No zero-order release, removal required for implants, potential toxicity if system fails.

Swelling-Controlled Systems

Dry system swells when it absorbs water or body fluids, increasing the solvent content within the formulation and enabling drug diffusion.
Common polymers used: hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC).
Drug release is controlled by the rate of polymer matrix swelling.
HPMC is a key polymer for hydrophilic matrices due to fast, uniform gel formation, providing a diffusional barrier to control release.

Erodible Systems

Two major advantages:
1. Polymers do not need to be removed from the body after drug delivery.
2. Drugs do not need to be water-soluble.

Biodegradable Polymers for Drug Delivery

Two types of biodegradation:
- Bulk erosion: Degradation occurs throughout the polymer by hydrolysis, breaking down large polymers into smaller biocompatible compounds.
- Surface erosion: Degradation occurs only at the polymer surface.
Factors affecting degradation:
- Chemical structure and composition
- Molecular weight
- Concentration
- Hydrophilicity/hydrophobicity
- Carrier size, shape, and porosity
- Additives
- Microenvironmental pH
- Method of preparation
- Sterilization
Examples of successfully used biodegradable polymers:
- Polylactic acid and polyglycolic acid
- Polycaprolactone (polyesters: aliphatic homo-polymer)
Common characteristics of biodegradable polymers:
- Stability with drug molecules
- Biocompatible and biodegradable
- Ease of large-scale manufacture
- Amenable to sterilization
- Flexibility for multiple release profiles

Polyesters in Drug Delivery

Polyesters and copolymers have been tested for injectable drug delivery.
Applications: implants, nanoparticles, and microspheres for delivering various drugs (narcotic antagonists, contraceptives, local anesthetics, cytotoxics, and antimalarial agents).

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Description

Explore the fundamentals of drug delivery systems, focusing on conventional and novel drug delivery methods. This quiz covers the mechanisms, limitations, and advancements in encapsulating drugs to enhance therapeutic effects. Ideal for students and professionals in pharmacology and related fields.