Controlled Drug Delivery Systems
Session Objectives
By the end of this session, students will be able to:
• Explain
controlled release dosage forms
• Discuss
the need controlled and sustained release systems
• Analyze
the physiological, physico-chemical and pharmaceutical factors in the design of CRDF
• Discuss
the various concepts of controlled release oral dosage forms
INTRODUCTION
What is drug
delivery systems?
The term “drug delivery systems’’ refer to the technology utilized to present the drug to the desired body site for drug release and absorption
Anatomy and Physiology
Digestive Processes
• Ingestion
• Propulsion
• Mechanical
digestion
• Chemical
digestion
• Absorption
• Distribution
• Biotransformation
• Defecation
Drug Delivery – Basic Concepts
The main aim of drug administration is
1.
Delivering
the drug to its site of action
2.
At a
determined rate and concentration
3.
Minimize
side-effects and maximize therapeutic effects
Until 1940s Conventional dosage forms essentially comprised:
• Oral
formulations (tablets, capsules solutions, suspensions, emulsions)
• Topical (Ointments, creams, pastes, gels, jellies)
• Injectables
( SVP, LVP, DPP)
Simple Conventional Dosage Forms – Disadvantages
• Oral
administration - many drugs, such as insulin, cannot be given by this route due to poor absorption
characteristics and/or propensity to
degrade in the gastrointestinal tract
• Topical
creams and ointments were limited to topical rather than systemic effects
• Parenteral
delivery - highly invasive, generally requires intervention by clinicians and the effects are usually
short-lived
Advances in Drug Delivery – 1950’s and 1990’s
• Introduction
of sustained-release delivery via the oral route
• Example
- Spansule capsule technology developed by Smith Kline and French Laboratories
• Spansule
consists of hundreds of tiny coated pellets of drug substance
• As
the pellets travel down the gastrointestinal tract, the coating material dissolves to release the drug
• By
using a capsule containing pellets incorporating a spectrum of different thickness coatings using single polymer or
same thickness of coat using different
polymers (and thus dissolution rates), sustained drug release of a given
pattern is possible
• Advent
of dedicated drug delivery research companies
• Advances
in the fields of biotechnology and molecular biology
• New
biopharmaceuticals, such as peptides, proteins and antisense oligonucleotides
Advances in Drug Delivery
• Recent research has been directed towards the use of alternatives to the parenteral
route, for drugs that cannot be delivered orally
• Potential
alternative portals of drug entry to the systemic circulation include buccal, sublingual, nasal, pulmonary and
vaginal routes
• These
routes are also being studied for the local delivery of drugs directly to
the site of action, thereby reducing the
dose needed to produce a pharmacological
effect and also possibly minimizing systemic side-effects
Ø Drug
delivery technology is becoming increasingly sophisticated
Current approaches take into account factors such as
Ø Influence
of pharmacokinetic processes on drug efficacy
Ø Importance
of drug timing and of drug targeting to the site of action
Emerging technologies are addressing a variety of issues
Ø Bio-responsive
drug release
Ø Delivery
of nucleic acid therapeutic entities
Summary
• Various
digestive processes are ingestion, propulsion, mechanical digestion, chemical
digestion, absorption and defecation
• Microscopic
anatomy of small intestine includes villi,
microvilli, crypts of lieberkuhn and Peyer’s patches.
• Oral
route of drug administration can be classified broadly into solid, liquid and semisolid dosage forms
• Drug
release from tablets can be for both immediate release ( sublingual & melt tablets) and slow release (conventional
tablets)
• Disintegration
is the rate limiting step for drug absorption from tablet preparation.
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