Dear Kevser,

The release of the drug from the DDS system depends on:

1-The HLB value of the drug (hydrophilic lipophilic balance).

2-The interactions between the drug and the components of the DDS system.

3-In case the DDS is a prodrug system, the release of the drug will be dependent on the physiological environment (enzymes and pH).

Hoping this will be helpful,

Rafik

Dear Kevser,

The release of the drug from the DDS system depends on:

1-The HLB value of the drug (hydrophilic lipophilic balance).

2-The interactions between the drug and the components of the DDS system.

3-In case the DDS is a prodrug system, the release of the drug will be dependent on the physiological environment (enzymes and pH).

Hoping this will be helpful,

Rafik

Dear Sevim,

Here is an article about your question..

Dear Kevser Sevim

In fact your question should be more specific as there is too many factors affecting the release process in addition to the drug hydrophobic nature, you may describe in more detail the problem so as the answers will be more informative. In addition to the previously mentioned notes,  you may need to be sure that you are doing the release study in the right way through the following few points:

First, by choosing the right release media that is comparable to the media where your formulation reaches its final destination and suppose to release the drug. If your release media is not compatible with the target media then your release experiment is unreliable.

secondly you have to check the stability of the drug in such release media, if not stable then you have to think on how to stabilize it first then perform the experiment.In addition to the stability in the media I suggest you to investigate the thermodynamic stability of the drug in the formulation and the media as well.

Third  sink conditions should be preserved throughout the whole experiment ( the ability of certain volume of the media to solubilize the expected amount of the drug) to make sure of this you need to do some preliminary experiments about the solubility of the drug of interest in such media.

fourth after making sure of the previous points you may look to the hydrophobicity of the drug and its effects on the release pattern from the formulation. no matter how hydrophobic is the drug there have to be certain limits of release in aqueous media and to detect this you have to use sensitive methods able to detect small amounts of the drug.

Fifth In some cases where we can not detect the drug in the media although we are sure from the above mentioned points then we may need to make sure the drug has been really loaded to our formulation and still there, to avoid any errors that may originate from the formulation itself rather than from the release study.

I hope these few points will be helpful 

regards 

Jumah

Thank you all for your valuable answers.

Regards.

Dear Kevser,

Drug release from DDS  is a complex phenomenon and it is a vast subject with depth. It is difficult to explain if all relevant factors are not considered quantitatively.Explanation varies from one set of conditions to other as variables are diffrent, and sometimes these effects are controlled by combined effects of two or more variables.

Following are the important points to be considered which affect dissolution of a drug with hydophobic nature.

1.extent of hydrphobicity, 2.saturation solubility, 3.concentration gradient manipulated by sink condition,4.total interfacial area surrounding particles,5.consideration of physicochemical properties of DDS system (matrix or network or porosity) , drug and eluting medium (viscosity, surface tension and density) , 6.matrix structure, 7.diffusion coefficient of drug, temperature of medium, 8.Agitation (rpm of stirrer) of medium , hydrodynamicity of the diffusion system.9. thickness of saturated layer surrounding the particle.  Besides these there may be other factors.

Ref.Books to be followed ,Martin's Physical Pharmacy, books on  Physical Chemistry .