•        Transport of water across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration

•         At equilibrium there no difference in osmotic pressure between both chambers and so there is no driving force for movement of solvent

•         Water/Solvent moves from solvent chamber to solution chamber to achieve equilibrium

•         When osmotic pressure of drug solution is approximately equal to osmotic pressure of biological fluids

Define Hypertonic solution

•         When osmotic pressure of drug solution is higher than osmotic pressure of biological fluids 

–        Mucosal membranes of GIT, blood-brain barrier (BBB), skin.  BBB and skin serve as strong barriers preventing entry or exit of molecules. Integrity of membrane is very important to serve their protective function 

   Describe synthetic barriers

Amount of material ‘M’ (g/mole) crossing a unit area ‘S’ (cm²

) in time ‘t’(s) 

Flux is proportional to   concentration gradient:

Define Diffusion coefficient

•         is a measure of the ease of permeability of molecules across the region. Negative sign – decrease in concentration as a function of distance. Flux is positive.

When concentration in receptor side is approximately zero 

•         No accumulation of drug 

•         greater than that inside the skin due to continuous absorption in the bloodstream, metabolism and elimination.

•         lower than that at the donor site

time required to saturate the membrane 

•         Lag time effect is generally seen when systems first come in contact with skin or mucosal tissue and depends on the membrane thickness

the initial rapid release of the drug 

•         Burst effect is seen in systems that have been stored for an extended period and the rate-controlling membrane is presaturated with the drug Depends on the thickness of the membrane and the diffuisivity of the drug 

•         the time required to saturate the membrane (lag-time) or the initial rapid release of the drug (burst-effect) from presaturated membranes

•         a polymeric membrane, polymeric or lipid matrix.  

•         Diffusion controlled devices could be of two types:

–        Pharmacological agent (drug) forms a core surrounded by an inert diffusion barrier (membrane)

Describe  Matrix devices (also known as monolithic devices):

Drug is dispersed or dissolved in an inert polymer or lipid

In diffusion controlled reservoir devices, the rate of drug diffusion through the polymeric membrane follows...

(Diffusion-controlled Reservoir Devices)

The rate of drug release is  dependent on... 

(Diffusion-controlled Reservoir Devices)

•         diffusion coefficient of the drug in the membrane, the available surface area, the membrane thickness and the drug concentration gradient. 

The structure that limits the rate of release of the drug is... 

(Diffusion-controlled Reservoir Devices)

•         the polymer layer surrounding the layer of the reservoir.

When the polymer coating is uniform and its the thickness remains unchanged and the concentration gradient is... 

(Diffusion-controlled Reservoir Devices)

constant ,the rate of diffusion of active ingredient can be kept fairly constant throughout the entire delivery time.

In diffusion controlled matrix devices, diffusion occurs when the drug passes from the... 

(Diffusion-controlled Matrix Devices)

•         matrix to the biological fluid.

 Also known as monolithic solution when... 

(Diffusion-controlled Matrix Devices)

when the drug is dispersed in the matrix system, it is called... 

(Diffusion-controlled Matrix Devices)

•         monolithic dispersion.

(Diffusion-controlled Matrix Devices)These type of devices does not usually provide ... 

•         zero order release.

As the drug molecule at the surface of the device is released, those in the center of the device have to....

(Diffusion-controlled Matrix Devices)

•         to travel longer distance to be released, which takes longer time

A decrease in release rate occurs because of... 

(Diffusion-controlled Matrix Devices)

•         the increase in diffusion time.

The movement of water results in the increase in pressure in the solution and the resulting osmotic pressure can be used to... 

(Osmosis Controlled Drug Release)

The device and formulation parameters can be controlled in order to achieve...

(Osmosis Controlled Drug Release)

•         zero order release.

Since these devices require osmotic pressure to be effective, the device operates essentially...

(Osmosis Controlled Drug Release)

The system consists of a single layer of tablet core containing a...  

(Elementary osmotic pump delivery system)

–        water-soluble drug with or without osmotic agents.

The core of the tablet is surrounded by... 

(Elementary osmotic pump delivery system)

semi-permeable membrane.

–        The membrane is drilled with a delivery orifice of 0.4 mm diameter.

What happens when such a system is swallowed?

(Elementary osmotic pump delivery system)

–        water from the  GIT enters the tablet core.

–        Water that enters the core dissolves the drug and the resultant drug solution is pumped out via the delivery orifice.

–        Only the drug solution is capable of passing through the hole in the tablet but not the undissolved drug.   

Why was Push-Pull osmotic system developed?

–        to overcome problems associated with poorly soluble drugs.

What is thePush-Pull osmotic system comprosied of?

–        a bilayer or trilayer tablet core consisting of one push layer and one or more drug layer.

The drug layer contains... 

(Push-Pull osmotic system)

–        poorly soluble drug and osmotically active hydrophilic polymers.

–        hydrophilic expansion polymer and other osmotically active agents.

     A  _______ surrounds the tablet core and an orifice is drilled in the membrane around the drug layer. 

Liquid Osmotic System contains...

–        This system consists of a soft gelatin capsule surrounded by a barrier layer, an osmotic push layer, and a semipermeable membrane.

–        This system is particularly useful for delivering insoluble drugs and macromolecules such as polysaccharides and peptides.

–        in solubilization, protection from enzymatic degradation and promotion of gastrointestinal absorption.