contented and precise , Drug delivery system , sustained release preparation.factors like absorption, distribution ,metabolism , therapeutic window , absorption window.

2. Oral administration of drug leads to loss of drug by acid hydrolysis
/metabolism in GIT.
It can be increased by formulating it
as sustained or controlled release
drug delivery system.
Enteric
coating of
the acid
hydrolysa
ble drug
Relative bioavailability of a drug that is
unstable in GI

3. OMEPRAZOLE is the victim of Acid hydrolysis.
So it is enteric coated to get devoid of acid
hydrolysis and it is converted into sustained
release preparation.
Relative bioavailability is increased
ultimately.

4. Vd is low
More drug in
blood
Less drug in
site
It is accessible to
elimination
process.
Vd is high Less drug in
blood
More drug in
site
It is not
accessible
to
elimination
process.

5. If the drug’s Apparent volume of
Distribution is GREATER than the REAL
volume of distribution
They are the poor canditates for sustained
release drug delivery system.
Example : chloroquine -12950
Digoxin- 500

6. Inactive drug Active
drug
METABOLISM
Drug treating
chronic disease
First pass
metabolis
m
Enzyme
induction
The drugs falls
under these
categories are
poor canditates
for sustained
release drug
delivery
system.
morphine

7. Drug having transit
time of 9 – 12 hours
through the absorptive
areas of GIT
Maximum absorption
half life - 3 to 4 hours
The rate of absorption
is 0.17- 0.23 % in a hour
So about 80- 95 %
absorption takes place.
Poor canditates for
sustained release drug
delivery system

8. Drug having slow rate of
absorption ie ka << 0.17 /hr
Drugs that follows first order
mechanisms
Drugs that erratically absorbed
due to variable absorption sites
Example
1.methotrexate
(absorbed by
active
transport)
2. misoprostol
Drugs need to
perform a lot of
therapeutic
actions in
stomach.

9. Drugs which absorb
only at SPECIFIC SITES.
Because of change in
environmental pH and
degradation of enzymes
Results in Differential drug
SOLUBILITY and STABILITY of the
drug.

10.  NORMAL SCENARIO ABNORMAL SCENARIO
Primary absorption site (70%)
Secondary absorption site
(30%)
Absorption window
Primary absorption site
(99%)
Secondary absorption
site (1%)
Narrow
absorptio
n window

11. Drugs that exhibiting site specific absorption
at STOMACH and UPPER PART OF INTESTINE
EX-Sulfonamides , Tetracyclines.

12. Half life is
increased
Volume of
distribution
increases
Increase in the
concentration
of drug in the
tissues.
Drug reaching the
elimination
process is
decreased.

13. DRUG CLEARANCE
(L/HR)
VOLUME OF
DISTRIBUTION(
L)
HALF-LIFE(HR)
MORPHINE 63.0 280 3.0
DIGOXIN 7.0 420 40.0
HALOPERIDOL 46.0 1400 20.0
CHLOROQUINE 45.0 12950 200.0

14. Long acting drugs are poor
canditates for SR
LISINOPRIL is the classical
example for this.

15. Drugs which have
shorter TI.
POOR canditates for
SR
Example –
Phenobarbitol-2.6

16.  Sustained release drug delivery systems have been a
gateway for various formulations such as
 Bupropion – Diffusion controlled release.
 Chlorpheniramine maleate – Osmotic pressure method.
 Hydrocodone polistirex and chlorpheniramine polistrex
– Ion exchange method.
 Proponalol- pH dependent formulation.

17.  Sustained release drug delivery system is very helpful
in increasing the efficiency of the dose safety of the
dose and primarily patient compliance.
 In addition to pills and other injectables sustained
release preparation of vaginal ring and contraceptive
implant has also been manufactured.
 Newer trend setting variety of formulations has been
arrived including Liposomes and Drug polymer
conjugates – HYDROGELS.

18.  Patient Compliance -Sustained release morphine
tablets enables the patient with chronic pain to take
one or two tablets per day.
 Metformin hydrochloride has relatively shorter half life
low absolute bioavailability .There is a need to take it
2-3 times a day that leads to larger dose it decreases
patient compliance.
 overcome : The conversion of conventional metformin
tablet to Sustained release metformin tablet improved
patient compliance.