2. CONTENTS
• 1. Introduction
• 2. Definitions
• 3. Rationale of Controlled DDS
• 4. Advantages of Controlled DDS
• 5. Disadvantages of Controlled DDS
• 6. Selection of drug candidate for Controlled DDS
3. INTRODUCTION
• 1. To achieve as well as to maintain the drug concentration
within the therapeutically effective range needed for
treatment, it is often necessary to take conventional drug
delivery system several times a day. This results in a
significant fluctuation in drug levels.
• 2. Recently, several technical advancements have been
made. They have resulted in the development of new
techniques for drug delivery. These techniques are capable
of controlling the rate of drug delivery, sustaining the
duration of therapeutic activity, and/or targeting the
delivery of drug to a tissue
4. DEFINITIONS:
• 1. Sustained-release:
• These are dosage forms designed to release (liberate) a drug at a predetermined rate in
order to maintain a constant drug concentration for a specific period of time with minimum
side effects
• Any of the dosage form that maintains therapeutic blood or tissue levels of drug by
continuous release of medication for a prolonged period of time, after administration of a
single dose.
• The onset of its pharmacologic action is often delayed, and the duration of its
therapeutic effect is sustained
• 2. Controlled-release:
• Controlled release dosage form is a dosage form that release one or more drugs
continuously in predetermined pattern for a fixed period of time, either systemically or locally
to specified target organ.
• Designed to slowly release a drug in the body in a prolonged controlled fashion.
• The release of drug ingredients from a controlled-release drug delivery system proceeds
at a rate profile that is not only predictable kinetically, but also reproducible from one unit to
another.
5. ADVANTAGES:
1. Total dose is low.
2. Reduced GI side effects and other toxic effects.
3. Reduced dosing frequency
4. Better patient acceptance and compliance.
5. Less fluctuation in plasma drug levels.
6. More uniform drug effect.
7. Better stability of drug and improved margin of safety.
8. Reduction in total health care cost.
6. DISADVANTAGES
1. Decreased system availability
2. Poor invitro-invivo correlation
3. Retrieval of drug is difficult in case of toxicity, poison or hyper-sensitivity reaction.
4. The physician has less flexibility in adjusting the dosage regimen.
5. This is fixed by dosage form design.
6. All drugs are not suitable candidates for controlled release medication.
7. Drugs with long biological half life (e.g. Digoxin-34 hours) are inherently long acting
and thus are viewed as questionable candidates for sustained release formulations.
7. Selection of drug
• Very short half life
• Drugs undergoing significant first pass hepatic metabolism
• Poor absorption through out the GIT
• Low solubility
• Large no of doses to be given
• Narrow therapeutic window (margin of safety of drug is very less or
the c max crosses the min toxic concentration)
