Dear Dr Alhamdany,

In order to answer your question accurately, we need to know more about the experimental condition (e.g. you microspheres components, your drug characteristics, concentration of your drug, medium in which your microspheres are suspended & its pH, initial and subsequent concentrations of added sodium bicarbonate, ...).

In general, effect of osmolarity, ionic strength and pH need to be looked along with the structure of your drug carriers.

Dear Dr. M.R. Mozafari

Thank you for your interest

Regarding the conditions, the drug is water soluble,the microspheres are floating,the pH of media is 1.2, the concentration of sodium bicarbonate is between 0.1%-0.8% in the formula

In general, the answer is based on polymer type. If the systems is swelling in the solvent the drug release rate is based on diffusion speed. If the system is not soluble, the release will be based on errosion. In first case, the release rate will slow down due to increased diffusion path and/or lower sink resulting in lower desorption. In second case, the drug accumulated near the surface will diffuse from particles (burst) and the following release will be based on erosion kinetics.

Thank you so much dear Dr.Matej Buzgo for your answer

But what is the cause of decreasing the release although sodium bicarbonate concentration increase and as it is expect to increase the drug release since sodium bicarbonate may facilitate erosion mechanism

Hi all,

What method you use for your drug quantification (e.g. is it through HPLC)?

Also, you mentioned pH: 1.2 (the initial medium of your microspheres); isn't this a deleterious condition for your drug integrity, potentially causing errors in quantification?

Dear Dr.Mozafari

Regarding the method of drug quantification, we use dissolution test

About the medium, it is considered as the best medium for drug release and absorbed in this medium especially for the floating drug delivery system, so we consider no error there.

The answer depends on the type and concentration of used polymer

Yes of course Dr.ashti..the polymer is the main motivator in controlling drug release but there is other factors also control drug release especially in floating drug delivery system and one of them is sodium bicarbonate

Dear Researcher

Two reasons are maily the cause

Firstly the polymeric type choosen or the polymeric blind

Lets suppose Eudrajet RS only is very slowly opened in media depending on the time causing slow drug release , however , co blinding with other polymer that is more permeable will enhance the release such as eudrajet RL or HPMC

Also the choice of the polymer is important for the intended goal , targeted deliverly mainly ph dependent so avoide time depe

The second factor is the drug polymer ratio of the same polymer, increasing the polymer amount will cause more retardation of the release so the optimum ratio of the drug to polymer is required for selected release

A third factor is the porosity of the formed particle and the presence of surface pores could facilitate the release

Thank you Noor Fareed for your interest and also to the nice answers