4. 1. Introduction
1. Osmotic drug delivery uses the osmotic pressure for
controlled delivery of drugs by using osmogens.
2. Osmosis : It refers to the process of movement of solvent
from lower concentration of solute towards higher
concentration of solute across the semipermeable
membrane.
3. Osmotic pressure: The pressure exerted by the flow of
water through a semipermeable membrane separating
two solutions with different concentrations of solute.
4. These systems can be used for both route of
administration i.e. oral and parenterals.
5. 2.Principle of osmosis
Abbe Nollet first reported osmotic effect in 1748, but Pfeffer
in 1877 had been the pioneer of quantitative measurement
of osmotic effect. Van’t Hoff established the analogy
between the Pfeffer results and the ideal gas laws by the
expression,
π = n2RT
Where,
n2 represents the molar concentration of sugar (or other
solute) in the solution,
R depicts the gas constant,
T the temperatue.
7. Osmotic Pressure Activated DDS
Semi-permeable
Membrane.
(cellulose esters)
Drug reservoir
( API + osmotic agent)
Delivery Orifice
8. For the drug delivery system containing a solution
formulation, the intrinsic rate of drug release is defined
by,
Q = Pw Am ( πs – πe )
t hm
For the drug delivery system containing a solid
formulation, the intrinsic rate of drug release is defined
by,
Q Pw Am ( πs – πe ) Sd
t = hm
9. Where,
Q/t - rate of drug release
Pw - permiability of semipermiable housing
Am -effective S.A. of semipermiable housing
hm - thickness of semipermiable housing
(π s - π e) – Differential osmotic pressure b/w DDS with osmotic
pressure ps & environmental osmotic pressure pe
Sd – Aqueous solubility of drug contained in the
solid formulation.
10. 3. Basic component of osmotic DDS
1. Drug : itself may act as osmogen otherwise osmogenic
salt can be added in formulation.
2. Semipermeable membrane: criteria: Sufficient wet
strength and water permeability Should be
biocompatible and rigid Should be sufficient thick to
withstand the pressure within the device Any polymer
that is permeable to water but impermeable to solute can
be used as a coating material in osmotic devices Ex.
Cellulose Acetate, Cellulose Triacetate and Ethyl
Cellulose.
3. Hydrophilic and hydrophobic polymers :( CMC, HEC,
HPMC )
13. 7.MARKETED PRODUCTS
1. Products Incorporating ALZA's OROS® Technology
A. Cardura® XL (doxazosin mesylate) sold in Germany for the
treatment of hypertension.
B. Covera-HS® (verapamil) a Controlled Release system for the
management of hypertension and angina pectoris.
C. Sudafed® (pseudoephedrine) for 24-hour relief of cold and
other respiratory allergies.
D. Procardia XL® (nifedipine) extended-release tablet for the
treatment of angina and hypertension.
2. Products Incorporating ALZA's DUROS® Implant
Technology
A. Viadur® (leuprolide acetate implant) delivers leuprolide
continuously for 12 months.
15. 9. Advantages
1. Zero order release
2. High release rate
3. High degree of IVIVC
4. Production scale up is easy
5. Increase efficacy of drug
6. Controlled drug delivery
7. Reduce dosing frequency
16. 10. Disadvantages
1. Expensive
2. Chance of toxicity due to dose dumping
3. Release of drug depends on :
- size of drug port
- surface area
- thickness and composition of membrane
18. Enzyme - Activated Drug Delivery System
(Classification By : Biochemical Means)
Activation-
Modulated
DDS
19. • This type of biochemical system depends on the enzymatic
process to activate the release of drug.
• Drug reservoir is either physically entrapped in microspheres
or chemically bound to polymer chains from biopolymers
(albumins or polypeptides).
• The release of drug is activated by enzymatic hydrolysis of
biopolymers (albumins or polypeptides) by specific enzyme
in target tissue.
20. Ex. Albumin microspheres release 5 – fluorouracil in a
controlled manner by protease – activated biodegradation.
