Pharmaceutical sciences

1. Sustained release and
controlled release Drug
Delivery System

2. Introduction
WHAT IS DRUG DELIVERY SYSTEMS?
Drug delivery system refer to the technology utilized to
present the drug to the desired body site for drug
release and absorption.
Newer discoveries and advancements in technology
has lead to various new techniques of delivering the
drugs for maximum patient compliance at minimal
dose and side effects.

3. …
Conventional drug delivery
In the conventional therapy aliquot quantities of drugs
are introduced into the system at specified intervals of
time with the result that there is considerable fluctuation
in drug concentration level as indicated in the figure.

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Ideal drug delivery
An ideal dosage regimen would be one, in which the
concentration of the drug, nearly coinciding with minimum
effective concentration (M.E.C.), is maintained at a constant
level throughout the treatment period. Such a situation can
be graphically represented by the following figure

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Objective
• Temporal drug delivery:
controlling the rate or specific time of drug
delivery to the target tissue.
• Spatial drug delivery:
targeting a drug to a specific organor tissue.

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First, it should deliver drug at a rate dictated by the
needs of the body over the period of the treatment.
Second it should channel the active entity solely to the
site of action.
This is achieved by development of new various
modified drug release dosage forms, like
● Sustained release drug delivery.
● Site specific and receptor targeting.
● Controlled release drug delivery.
● Timed release or Delay release.etc

7. SUSTAINED RELEASE DRUG DELIVERY: Any of the dosage form that
maintains the therapeutic blood or tissue levels of drug by continuous
release of medication for a prolonged period of time, after administration
of a single dose. In case of injectable dosage forms it may vary from days
to months.
SITE SPECIFIC AND RECEPTOR TARGETING : Targeting a drug
directly to a certain biological location .For site specific release the target
is the adjacent to or in the diseased organ or tissue, for receptor release
the target is the particular drug receptor within an organ or tissue.
CONTROLLED RELEASE DRUG DELIVERY :Delivery of the drug at a
predetermined rate and /or to a location according to the needs of the
body and disease states for a definite period of time.

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▣ TIMED RELEASE OR DELAYED RELEASE: These are the systems
that use repetitive, intermittent dosing of a drug from one or more
immediate release units incorporated into a single dosage form or an
enteric delayed release systems e.g. Repeat action tablets and
capsules and enteric coated tablets where time release is achieved by
barrier coating, or wherein the release of the drug is intentionally
delayed until it reaches the intestinal environment.
▣ REPEAT ACTION DOSAGE FORM: contain 2 or 3 full doses which
are so designed that the doses are released sequentially one after the
other.
▣ OTHER NOVEL(NEW) DOSAGE FORMS:includes- Microspheres,
Nanoparticles,, Trans-dermal delivery systems, Ocular drug delivery,

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History
The history of controlled release technology is divided
into three time periods
1)From 1950 to 1970 was the period of sustain drug
release.
●In 1952, Beecham introduced the first sustained
release formulation that was able to control the drug
release kinetics and achieve 12-hour efficacy.
●The goal in designing sustained release drug delivery
system is to reduce the frequency of the dosing, reducing
the dose & providing uniform drug Delivery.

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2) From 1970 to 1990 was involved in the
determination of the needs of the control drug
delivery.
3)Post 1990 modern era of controlled release
technology.

11. Comparison...

12. Sustained release dosage form
“Drug Delivery system that are designed to achieve
prolonged therapeutic effect by continuously
releasing medication over an extended period of time
after administration of single dose.”
The basic goal of therapy is to achieve steady state blood
level that is therapeutically effective and non toxic for
an extended period of time.
The design of proper dosage regimen is an important
element in accomplishing this goal.
Also referred to as prolonged-release (PR), slow
release (SR), sustained action (SA), prolonged
action (PA) or extended-release (ER).

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Sustained release tablets are generally taken once
or twice a day during a course of treatment
whereas in conventional dosage forms there is
need to take 3-4 times dosage in a day to
achieve the same therapeutic action .
Sustained release formulation maintains a
uniform blood level of drug with better patient
compliance as well as increased efficacy of
drug

14. Comparison of drug release profile

15. Difference between sustained
release and controlled release

16. Rationality in designing
S.R.Dosage form
Rationality in designing S.R.Dosage form.
The basic objective in dosage form design is to
optimize the delivery of medication to achieve
the control of therapeutic effect in the face of
uncertain fluctuation in the vivo environment
in which drug release take place.
This is usually concerned with maximum drug
availability by attempting to attain a maximum
rate and extent of drug absorption however,
control of drug action through formulation also
implies controlling bioavailability to reduce
drug absorption rates.

17. Concept of sustained release
formulation
The Concept of sustained release formulation can
be divided in to two considerations i.e. release
rate & dose consideration
A) Release rate consideration :-
In conventional dosage form Kr>Ka in this the
release of drug from dosage form is not rate
limiting step.
The above criteria i.e. (Kr>Ka) is in case of
immediate release,where as in non immediate
(Kr<Ka) i.e. release is rate limiting step.

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So that effort for developing S.R.F must be
directed primarily altering the release rate. the
rate should be independent of drug removing in
the dosage form over constant time.
The release rate should follow zero order kinetics
Kr = rate in = rate out = KeVd.Cd
Where
Ke = overall elimination (first order kinetics).
Vd = total volume of distribution.
Cd = desired drug concentration.

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B) Dose consideration :-
To achieve the therapeutic level & sustain for a given
period of time for the dosage form generally consist
of 2 part
a) Initial (primary) dose nb) maintenance dose
there for the total dose ‘W’ can be.
W = Di + Dm
In a system, the therapeutic dose release follows zero
orderprocess for specified time period then,
W= Di + K°r. Td
Td = time desired for sustained release from one
dose.

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▣ If maintenance dose begins to release the drug
during dosing t=0 then,
▣ W = Di + K°r Td – K°r Tp
▣ Tp = time of peak drug level.
▣ However a constant drug can be obtained by
suitable combination of Di & Dm that release the
drug by first order process, then
▣ W = Di + ( Ke Cd /Kr ) Vd

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Sustained release, sustained action, prolonged
action,controlled release, extended action, time
release dosage formed areterms used to identify
drug delivery system that are designed to
achieve a prolonged therapeutic effect by
continuously releasing medication over an
extended period of time after administration of
single dose .
In case of injectable dosage form, this period
may vary from days to month, in case of orally
administrated forms,however, this period is
measured in hours & critically depends on the
residence time of the dosage form in GI tract.

22. Advantages
➢Improved patient convenience and compliance due to
less frequent drug administration.
➢Reduction in fluctuation in steady-state level and
therefore better control of disease condition.
➢Increased safety margin of high potency drug due to
better control of plasma levels.
➢Maximum utilization of drug enabling reduction in
total amount of dose administered.

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➢Reduction in health care cost through improved
therapy, shorter treatment period.
➢Less frequency of dosing and reduction in
personnel time to dispense, administer monitor
patients.
➢Better control of drug absorption can be
obtained, since the high blood level peaks that
may be observed after administration of a
dose of high availability drug can be reduced.

24. Disadvantages
➢Decreased systemic availability in comparisn to
immediate release conventional dosage forms;
this may be due to incomplete release, increased
first-pass metabolism, increased
instability,insufficient residence time for
complete release, site specific absorption, pH
dependent solubility etc.,
➢Poor in-vivo, in-vitro correlation.
➢Possibility of dose dumping due to food,
physiologic or formulation variable or chewing
or grinding of oral formulation bythe patient and
thus increased risk of toxicity.

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➢Retrieval of drug is difficult in case of toxicity,
poisoning or hypersensitivity reaction.
➢The physician has less flexibility in adjusting
dosage regimens.This is fixed by the dosage
form design.
➢Economics factors must also be assessed, since
more costly processes and equipment are
involved in manufacturing many sustained
release forms.
➢

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