controlled and sustained release dosage form/controlled release dosage form/suistained release...

10
CONTROLLED AND SUSTAINED RELEASE DOSAGE FORM INTRODUCTION 1. CONTROLLED RELEASE DOSAGE FORM Controlled drug delivery is one which delivers the drug at a predetermined rate, for locally or systemically, for a specified period of time. Continuous oral delivery of drugs at predictable & reproducible kinetics for predetermined period throughout the course of GIT. 2. SUSTAINED RELEASE DOSAGE FORM Sustained drug delivery may provide an immediate dose required for the normal therapeutic response, followed by the gradual release of drug in amounts sufficient to maintain the therapeutic response for a specific extended period of time usually 8-12 hours.

Upload: ashwani-kumar-singh

Post on 21-Apr-2017

277 views

Category:

Education


9 download

TRANSCRIPT

Page 1: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

CONTROLLED AND SUSTAINED RELEASE DOSAGE FORM

INTRODUCTION

1. CONTROLLED RELEASE DOSAGE FORM

• Controlled drug delivery is one which delivers the drug at a predetermined rate, for locally or systemically, for a specified period of time.

• Continuous oral delivery of drugs at predictable & reproducible kinetics for predetermined period throughout the course of GIT.

2. SUSTAINED RELEASE DOSAGE FORM

• Sustained drug delivery may provide an immediate dose required for the normal therapeutic response, followed by the gradual release of drug in amounts sufficient to maintain the therapeutic response for a specific extended period of time usually 8-12 hours.

Page 2: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

Differences between sustained and controlled drug delivery system

Sustained release dosage form Controlled release dosage form

1. Constitutes dosage form that provides medication over extended period of time

2. SRDF generally do not attain zero order release kinetics

3. Usually do not contain mechanisms to promote localization of the drug at active site.

1. Constitutes dosage form that maintains constant drug levels in blood or tissue

2. Maintains constant drug levels in the blood target tissue usually by releasing the drug in a zero order pattern.

3. Controlled dosage forms contain methods to promote localization of the drug at active site.

Page 3: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

Comparison of Drug Release Profile

Page 4: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

1. Diffusion

• Major process for absorption.• No energy required.• Drug molecules diffuse from a region of higher concentration to

lower concentration until equilibrium is attained.• They are of 2 types:

1. Matrix diffusion system 2. Reservoir diffusion system

•The drug is released either by passing through the pores or between polymer chains.

•Example- Such as polyehylene, polyvinylacetate.

•The drug is contained in a core, which is surrounded by a polymer membrane, and it is released by diffusion through rate- controlling membrane.

• e.g. Poly(N-vinyl pyrrolidone), Poly(ethylene-co-vinyl acetate).

Mechanism aspects of controlled and Sustained release

Page 5: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

2. Dissolution • It is of 2 types:1. Matrix Type 2. Encapsulation•Also called as Monolith dissolution controlled system.•Controlled dissolution by: 1.Altering porosity of tablet.2.Decreasing its wettebility.3.Dissolving at slower rate.•First order drug release.•Drug release determined by dissolution rate of polymer.•Examples: Dimetane extencaps.

•Called as Coating dissolution controlled system.•Dissolution rate of coat depends upon stability & thickness of coating.•Masks colour, odour, taste, minimising GI irritation.•Examples: Ornade spansules.

Soluble drug

Slowly dissolving matrix

Soluble drug

Slowly dissolving or erodible coat

Page 6: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

3. Osmotic Pressure Controlled System

• Provides zero order release

• Drug may be osmotically active, or combined with an osmotically active salt (e.g., NaCl).

• Semipermeable membrane usually made from cellulose acetate.

• More suitable for hydrophilic drug.

• Examples: Glucotrol XL, Procardia XL.

4. Water penetration (swelling)

• This type of systems are initially dry and when placed in body, absorb water or other fluid and it swells.

• Swelling increases aq. solvent content within the formulation as well as the polymer mesh size, enabling the drug to diffuse through the swollen network into external environment.

• E.g(N-isopro-pylacrylamide), Ethylene-vinyl alcohol

Page 7: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

Advantages and disadvantages of controlled release and sustained release

Advantages Disadvantages• Total dose is low.

• Reduced GI side effects.

• Reduced dosing frequency.

• Better patient acceptance and compliance.

• Less fluctuation at plasma drug levels.

• More uniform drug effect

• Improved efficacy/safety ratio.

• Dose dumping.

• Reduced potential for accurate dose adjustment.

• Need of additional patient education.

• Stability problem.

• The physician has less flexibility in adjusting dosage regimen, as it is fixed by dosage form design.

Page 8: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

EXAMPLES OF Controlled and Susatained Release Dosage Forms

1. Transdermal patches

• A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream. Often, this promotes healing to an injured area of the body.

Advantages Disadvantages

1. Topical patches are a painless way to deliver substance directly into the body.

2. Topical patches are cost effective , and preferable with fewer side effect.

3. They are controlled, steady dellivary of medication over long periods of time.

1. It cannot achive high drug levels in blood/plasma.

2. It cannot deliver ionic drugs, and cannot develop for drugs of large molecular size.

3. It cannot deliver drugs in a pulsatile fashion.

Page 9: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

2. Implants• An implant is a medical device manufactured to replace a missing

biological structure, support a damaged biological structure, or enhance an existing biological structure.

Advantages Disadvantages1. Convenience- effective

concentration of drug in the blood can be maintained for longer period of time.

2. Improved drug delivery- Drug is distributed in systemic ciculation with least interference by metabolic or biological barrier.

3. Compliance- By allowing complete elimination, of patient-involved dosing compliance is increased.

1. Invasive- to initiate therapy either a minor or a major surical procedure is required to initiate therapy.

2. Danger of device failure- If device may for some reason fails to work, it requires surgical involvement to correct.

3. Limited to potent drug- The size of implant is small, therefore implants have potent medicine like hormones in limited loading capicity.

Page 10: Controlled and sustained release dosage form/CONTROLLED RELEASE DOSAGE FORM/SUISTAINED RELEASE DOSAGE FORM

3. Liposomes

• Liposomes is an artificial vesicle composed of one or more concentric phospholipid bilayers and used especially to deliver microscopic substances to body cells.

Advantages Disadvantages 1. Liposomes are biocompatible,

completely biodegradable, non-toxic and non-immunogenic for systemic and non-systemic administrations.

2. Liposomes are increased efficacy and therapeutic index of drug.

3. Liposomes helps to reduce exposure of sensitive tissue to toxic drugs.

1. The production cost is high, they have short half-life

2. Liposomes have low solublity, leakage and fusion of encapsulated drug molecules.

3. Sometimes phospholipid undergoes oxidation and hydrolysis like reaction.