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


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



       Mechanical digestion

       Chemical digestion





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


       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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