Controlled Drug Delivery Systems

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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