Implants are small sterile masses made through compression, molding, or extrusion to deliver drugs at a controlled rate over a prolonged period. They are normally 2-3 mm in diameter and rod-shaped with a polymeric inner matrix. Implants have benefits like targeted delivery, reduced side effects, improved stability and compliance, and controlled long-term release. Potential issues include minor surgery for insertion, difficulty removing once inserted, and local irritation at the application site.

2. • Implants are small sterile masses which are highly purified made by compression,
molding , extrusion.
• These implants mainly intended for intramuscular , subcutaneous by minor incision
or injected by large bore needle.
• Ability to deliver drug at controlled rate over a prolonged period of time and the
order of kinetics is first order kinetics.
• They are normally about 2-3 mm in diameter.
• These mainly comprises of rod shaped polymeric inner matrix with an elongated
body and two ends.

3. 1. They are target specific
2. Decrease side effects and bypass the first path metabolism (FPM).
3. Improved stability.
4. Controlled release over a long period of time.
5. Improved patient compliance.
6. Better availability of drugs.

4. 1. Minor surgery is needed so process is slightly painful.
2. Long therapy can not be discontinued easily.
3. Reaction may take place between host and implant.
4. Inadequate release of API may take place.
5. May cause local irritation on the application site.

6.  CONTROLLED DRUG DELIVERY
BY DIFUSSION

7. • In this type of preprogrammed drug delivery
systems, a drug formulation is totally or partially
encapsulated within a drug reservoir
compartment. Its drug release surface is covered
by a rate-controlling polymeric membrane
having a specific permeability. The drug
reservoir may exist in solid, suspension, or
solution form
• In the Progestasert WD, an intrauterine device, the drug
reservoir is a suspension of progesterone crystals in
silicone medical fluid and is encapsulated in the vertical
limb of a T-shaped device walled by a nonporous
membrane of ethylenevinyl acetate copolymer.
Example-

8. In the Ocusert system (an ocular insert) the drug
reservoir is a thin disk of pilocarpine alginate
complex sandwiched between two transparent
sheets of microporous ethylene-vinyl acetate
copolymer membrane The microporous membranes
permit the tear fluid to penetrate into the drug
reservoir compartment to dissolve pilocarpine from
the complex. By system design, pilocarpine molecules
are then released at a constant rate of either 20 or 40
micro gram/hour for the management of glaucoma
for up to 7 days.

9. • In this type of preprogrammed drug delivery
system the drug reservoir is prepared by
homogeneously dispersing drug particles in a rate-
controlling polymer matrix fabricated from either a
lipophilic or a hydrophilic polymer. The drug
dispersion in the polymer matrix is accomplished
by either (1) blending a therapeutic dose of finely
ground drug particles with a liquid polymer or a
highly viscous base polymer, followed by cross-
linking of the polymer chains, or (2) mixing drug
solids with a rubbery polymer at an elevated
temperature.
• Nitro-Dur is a transdermal drug delivery (TDD) system
fabricated by first heating an aqueous solution of
water-soluble polymer, glycerol, and polyvinyl alcohol.
• The temperature of the solution is then gradually
lowered and nitroglycerin and lactose triturate are
dispersed just above the congealing temperature of the
solution.
Example -

10. • In this type of preprogrammed drug delivery systems the
drug reservoir is fabricated by micro dispersion of an
aqueous suspension of drug using a high-energy dispersion
technique (22-24) in a biocompatible polymer, such as
silicone elastomers, to forma homogeneous dispersion of
many discrete, unleachable , microscopic drug reservoirs.
Different shapes and sizes of drug delivery devices can be
fabricated from this micro reservoir drug delivery system by
molding or extrusion
Example-
• Estradiol transdermal
contraceptive

11. o Osmotic pump
This type of activation-controlled drug delivery system
depends on osmotic pressure to activate the release of
drug. In this system the drug reservoir, which can be
either
a solution or a solid formulation, is contained within a
semipermeable housing with controlled water
permeability. The drug is activated to release in solution
form at a constant rate through a special delivery orifice.
The rate of drug release is modulated by controlling the
gradient of osmotic pressure.
Example-
Acutrim tablet, an oral rate-controlled drug delivery
device, is a solid tablet of water-soluble and osmotically
active phenylpropanolamine (PPA) HC1 enclosed
within a semipermeable membrane made from
cellulose triacetate (39,40).

12. • In this type of drug delivery system the drug reservoir, which
also exists as a solution formulation, is contained inside the
infusion compartment. It is physically separated from the
pumping compartment by a freely movable partition . The
pumping compartment contains a fluorocarbon fluid that
vaporizes at body temperature at the implantation site and
creates a vapor pressure. Under the vapor pressure created the
partition moves upward. This forces the drug solution in the
infusion compartment to be delivered through a series off low
regulator and delivery cannula into the blood circulation at a
constant flow rate.
Example-
• Infusion pump of heparin in
anticoagulation treatment

13. • In this type of activation-controlled drug delivery
system the drug reservoir is a dispersion of peptide or
protein powders in a polymer matrix from which
macromolecular drug can be delivered only at a
relatively slow rate. This low rate of delivery can be
improved by incorporating an electromagnetically
triggered vibration mechanism into the polymeric
delivery device

14. • In this system the drug reservoir is
homogeneously dispersed in a
swellable polymer matrix fabricated
from a hydrophilic polymer. The
release of drug is controlled by the rate
of swelling of the polymer matrix.
Example-
• The Valrelease (Diazepam) tablet is prepared by a
simple pharmaceutical granulation process of
homogeneous dispersion of Valium, a tranquilizer,
in hydrocolloid and pharmaceutical excipients.

15. • This type of activation-controlled drug delivery
system depends on the hydrolysis process to activate
the release of drug molecules. In this system the
drug reservoir is either encapsulated in
microcapsules or homogeneously dispersed in
microspheres or nanoparticles for injection .
Example-
• A typical example of a hydrolysis-activated drug
delivery system is the development of LHRH-
releasing biodegradable subdermal implant,
which is designed to deliver goserelin, a
synthetic LHRH analog, for once-a-month
treatment of prostate carcinoma.

16. • Bioerosion
o The feedback-regulated drug delivery concept was applied to
the development of a bioerosion-regulated drug delivery system
by Heller and Trescony (68) .
o The system consisted of drug-dispersed bio erodible matrix
fabricated from polyvinyl methyl ether)half-ester, which was
coated with a layer of immobilized urease In a solution with
near neutral pH, the polymer only erodes very slowly. In the
presence of urea, urease at the surface of drug delivery system
metabolizes urea to form ammonia . This causes the pH to
increase and a rapid degradation of polymer matrix as well as
the release of drug molecules.

17. o The feedback-regulated drag delivery concept has also been applied to the development of a bio
responsive drug delivery system by Horbett et al. (69).
o In this system the drug reservoir is contained in a device enclosed by a bio responsive polymeric
membrane whose drug permeability is controlled by the concentration of a biochemical agent in the
tissue where the system is located.
Example-
o A typical example of this bio responsive drug delivery system is the development of a glucose-triggered
insulin delivery system in which the insulin reservoir is encapsulated within a hydrogel membrane
having pendant NR2 groups . In alkaline solution the — NR2 groups are neutral and the membrane is
unswollen and impermeable to insulin. As glucose, a triggering agent, penetrates into the membrane, it
is oxidized enzymatically by the glucose oxidase entrapped in the -

18. -membrane to form gluconic acid. The — NR2 groups are
protonated to form -NR2H+, and the hydrogel membrane
then becomes swollen and permeable to insulin molecules
The amount of insulin delivered is thus bio responsive to the
concentration of glucose penetrating the insulin delivery
system.