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Simulations Plus FAQ Section
Please select the product you are interested in by using the pull down menu on the left.
Question:  How do I create a New Record?
Answer:  

1. Click on the Database menu.

2. Select Create New Formulation Record.

3. Type in the name of the new formulation record and select the dosage form in the dialog box that appears.

4. Close the dialog box.



Question:  How do I save changes to my database?
Answer:  

1. Click on the Database menu.

2. Select Save Formulation Record.



Question:  How can I perform database operations like copy, delete, find, rename?
Answer:  

You can perform all these database operations by clicking on the Database menu. You will then get a list of available options.



Question:  Can I enter multiple pKa's for compounds?
Answer:  

Yes. You can enter multiple pKa's for compounds. Each pKa has to be entered one-line each. You can select the compound from the column drop-down.



Question:  How do I set Diffusion Layer Thickness?
Answer:  

1. Click on the Simulation Setup menu.

2. Select Set Diffusion Layer Thickness.

3. Enter the thickness in microns.
4. Click OK.

Note: The thickness is set for that particular formulation record. The default is 30 microns.
Question:  How can I create my own dissolution media (buffers)?
Answer:  

To create dissolution media (buffers) please see the Medium Formulation Compositiom section under the Experimental Setup Tab in the ADMET Predictor User manual.



Question:  How can I set/unset a constant medium pH?
Answer:  

To set constant pH: Under the Experimental Setup Tab, select the textbox corresponding to the Medium pH. Then enter the desired pH. This will set a constant dissolution media pH throughout the simulation.

 

If you have experimental phases (more than one stage) then click on the Experiment Phase button and select the checkbox on the top right corner (under Med pH column). This will enable a constant pH for phased experiment. Then enter the desired pH for each stage.

To unset constant pH: Under the Experimental Setup Tab, click on the Experiment Phase button and un-select the checkbox on the top right corner (under Med pH column).



Question:  How do I enable/disable microclimate pH?
Answer:  

2. Click on the Simulation Setup menu.

2. Select/Unselect Use Microclimate pH option.



Question:  Can I use surfactants in dissolution media?
Answer:  

1. Under the Experimental Setup Tab, click on the Medium Composition button.

2. Now click on the Surfactant button.

3. You have the ability to add a maximum of two surfactants per buffer. (eg: FaSSIF, FeSSIF)

 

Note: To remove surfactant select "None" under the surfactant drop-down.



Question:  How can I add medium pH parameter to PSA and Optmization Modules?
Answer:   You will need to set a constant pH in order to invoke the medium pH parameter to the PSA and Optimization Modules. To set a constant pH please see this FAQ above.

Question:  How do I input my own Particle Size data?
Answer:  

1. Click on the File menu.

2. Select Load and then Load Particle Size Distribution.

3. Now select the corresponding Ingredient from the drop-down, enter the number of bins and type the data in the grid.

4. Select File Menu, click Save.



Question:  How do I input my own solubility-pH data?
Answer:  

1. Click on the File menu.

2. Select Load and then Solubility vs. pH Data.

3. Now select the corresponding Ingredient from the drop-down, enter the number of data points and type the data in the grid.

4. Select File Menu, click Save.



Question:  Is there a conversion tool to convert a parameter from one unit to another?
Answer:  

Yes! If you would like to convert %Weight to Molar Concentration or get an estimate of the Diffusion Coefficient from Molecular Weight etc,

 

2. Click on the File menu.

2. Select Conversion Tool option.



Question:  I changed the Mean Particle Radius and Standard Deviation but the percent dissolved remains the same.
Answer:  

Under the Simulation Tab, locate the 'PSD Calculation' option you are currently using. If the 'Load .psd file' option is selected you will not see any change in the simulated profile for changes in particle radius or standard deviation.

 

(OR) For this particular compound/formulation there is no real effect on the particle size factor (For example: a highly insoluble ingredient will have little effect on changes to particle size).



Question:  I changed the pKa's of the compound but the percent dissolved remains the same
Answer:  

Under the Simulation Tab, locate the 'Solubility Calculation' option you are currently using. If the 'Load .spd file' option is selected you will not see any change in the simulated profile for changes in pKa.

 

(OR) For this formulation that particular change in pKa value has no net effect/change in pH of the dissolution media, hence no significant change to solubility (For example: a compound with acidic pKa of 1.5 will not have any effect on pH of a concentrated HCl dissolution media).



Question:  For a swellable Polymer Matrix dosage form, is Release Exponent an important parameter?
Answer:  

Yes! Release Exponent reflects the swelling/erosion characteristics of the polymer matrix.



Question:  Certain simulations are slow, why?
Answer:  

DDDPlus computes very complex equations like particle size, pH, solubility, rate of dissolution, etc. for each of the ingredients in the formulation along the entire course of the simulation. These are highly complex tasks and solving the differential equations depends on the nature of the system (formulation parameters and experiment conditions).



Question:  My simulation is under-predicted, why?
Answer:  

Did you Optimize the formulation record? If not click here to see how to run an optimization. For examples click here

 

If the simulation is still under-predicted, check the following items belows:

 

1. Physicochemical properties of all the formulation ingredients.

2. Particle Size Distribution and the PSD Calculation Option.

3. pKa's of all the ingredients.

4. The correct Solubility Factors have been entered (maybe you have a low solubility factors).

5. The correct solubility corresponding to the pH of the dissolution media has been entered correctly.

6. The calibration constant(s) and the 'excipient' constant(s) have been optimized.

7. The constant pH is turned off.

8. The Instrument Speed and Medium Volume is entered correctly.

9. A smaller Diffusion Layer Thickness may be needed. The default is 30 microns.

If the problem is still unresolved, please contact Simulations Plus.

 



Question:  My simulation is over-predicted, why?
Answer:  

Did you Optimize the formulation record? If not click here to see how to run an optimization. For examples click here

 

If the simulation is still under-predicted, check the following items below:

 

1. The Physicochemical properties of all the formulation ingredients.

2. The Particle Size Distribution and the PSD Calculation Option.

3. The pKa's of all the ingredients.

4. The correct Solubility Factors have been entered (maybe you have a high solubility factors).

5. The solubility corresponding to the  pH of the dissolution media has been entered correctly.

6. The calibration constant(s) and the 'excipient' constant(s) have been optimized.

7. The constant pH is turned off.

8. Instrument Speed and Medium Volume is entered correctly.

9. A larger Diffusion Layer Thickness. The default is 30 microns.

 

If the problem is still unresolved, please contact Simulations Plus, Inc.



Question:  Can DDDPlus simulate predictions for my drug?
Answer:   Yes absolutely!  You can create formulation databases and create records with different combinations of formulations to predict the dissolution behavior.

Question:  How do I create a New Formulation Database?
Answer:  

To create a New Database,

  1. Click on the File menu.
  2. Select New Formulation Database.
  3. Type in the name of the new formulation database in the dialog box that appears.
  4. Click Open button on the dialog box.


Question:  How do I create a New Formulation Record?
Answer:  

To create a New Formulation Record,

  1. Click on the Database menu.
  2. Select 1 CreateNew Formulation Record.
  3. Type in the name of the new formulation record and select the dosage form in the dialog box that appears.
  4. Click OK button.


Question:  How do I save changes to my database?
Answer:  

To save changes to a Formulation Record,

  1. Click on the Database menu.
  2. Select 3Save Formulation Record.


Question:  How can I perform database operations like copy, view/edit, subset, delete?
Answer:   You can perform all these database operations by clicking on the Database menu. You will then get a list of available options.

Question:  Can I enter multiple pKa's for compounds?
Answer:   Yes.  You can enter multiple pKa's for compounds.  Each pKa has to be entered one-line each.  You can select the compound from the column drop-down.

Question:  How do I set Diffusion Layer Thickness?
Answer:  

To set the Diffusion Layer Thickness,

  1. Click on the Simulation Setup menu.
  2. Select 3 Dissolution Model
  3. Select 1Set Diffusion Layer Thickness.
  4. Enter the thickness in microns.
  5. Click OK.
Note: The thickness is set for that particular formulation record.  The default is 30 microns.

Question:  How can I set/unset a constant medium pH?
Answer:   To set constant pH, u nder the Experimental Setup Tab, select the textbox corresponding to the Medium pH.  Then enter the desired pH and the textbox becomes yellow.  This will set a constant dissolution media pH throughout the simulation.

If you have experimental phases (more than one stage) then click on the Experiment Phase button and select the checkbox on the top right corner (under Med pH column).  This will enable a constant pH for all phases of the experiment.  Then enter the desired pH for each stage.

To unset constant pH, under the Experimental Setup Tab, click on the Experiment Phase button and un-select the checkbox at the top right corner (under Med pH column).

Question:  How do I enable/disable microclimate pH?
Answer:  

To enable/disable microclimate pH option,

  1. Click on the Simulation Setup menu.
  2. Select 3 Dissolution Model
  3. Select/Unselect 2Use Microclimate pH option.


Question:  Can I use surfactants in dissolution media?
Answer:  

To add surfactant to the dissolution media (buffer),

  1. Under the Experimental Setup Tab, click on the Medium Composition button.
  2. Now click on the Surfactant button.

You have the ability to add a maximum of two surfactants per buffer. (eg: FaSSIF, FeSSIF)

Note: To remove surfactant select "None" under the surfactant drop-down.



Question:  How can I add medium pH parameter to PSA and Optmization Modules?
Answer:   You will need to set a constant pH in order to invoke the medium pH parameter to the PSA and Optimization Modules.  To set a constant pH please see this FAQ above.  

Question:  How do I input my own Particle Size data?
Answer:  

If you like to enter your customized particle size data,

  1. Click on the File menu.
  2. Select Load and then3 Load Particle Size Distribution Data (.psd).
  3. Now select the corresponding Ingredient from the drop-down, enter the number of bins and type the data in the grid.
  4. Select the File Menu and click Save.


Question:  How do I input my own solubility-pH data?
Answer:  

If you like to enter your solubility-pH data,

  1. Click on the File menu.
  2. Select Load and then2 Load Solubility vs. pH Data (.spd).
  3. Now select the corresponding Ingredient from the drop-down, enter the number of data points and type the data in the grid.
Select the File Menu and click Save.

Question:  Is there a conversion tool to convert a parameter from one unit to another?
Answer:  

Yes!  If you would like to convert %Weight to Molar Concentration or get an estimate of the Diffusion Coefficient from Molecular Weight etc.,

  1. Click on the Tool menu.
  2. Select Conversion Tool option.


Question:  I changed the Mean Particle Radius and Standard Deviation but the percent dissolved remains the same.
Answer:  

Answer:   Under the Simulation Tab, see the 'PSD Calculation' option you are currently using.  If the 'Load .psd file' option is selected you will not see any change in the simulated profile for changes in particle radius or standard deviation.

(OR) For this particular compound/formulation there is no real effect on the particle size factor (For example: Particle size affects the dissolution rate, not the actual solubility of the compound.  So if your compound is highly soluble or highly insoluble in the dissolution media or if the dissolution media reaches the saturation limit before the end of simulation, you may not see any significant change in the simulated profile).



Question:  I changed the pKa's of the compound but the percent dissolved remains the same
Answer:   Under the Simulation Tab, see the 'Solubility Calculation' option you are currently using.  If the 'Load .spd file' option is selected you will not see any change in the simulated profile for changes in pKa.

(OR) For this formulation that particular change in pKa value has no net effect/change in pH of the dissolution media, hence no significant change to solubility (For example: a compound with acidic pKa of 1.5 will not have any effect on pH of a concentrated HCl dissolution media i.e., in other words the dissolution media has a high buffer capacity and the dissolving compound is unable to effect the pH of the media).

Question:  For the Polymer Matrix (Swellable) dosage form, is Release Exponent an important parameter?
Answer:  

Yes!  Release Exponent controls the swelling/erosion behavior of the polymer matrix.



Question:  Certain simulations are slow, why?
Answer:  

DDDPlus computes very complex equations like particle size, pH, solubilities, rate of dissolution etc. for each of the ingredients in the formulation along the entire course of the simulation.  These are highly complex tasks and solving the differential equations depends on the nature of the system (formulation parameters and experiment conditions).



Question:  My simulation is under-predicted, why?
Answer:  

Did you Optimize the formulation record?  If the simulation is still under-predicted follow the following steps:

  1. Check the physicochemical properties of all the formulation ingredients.
  2. Check the Particle Size Distribution and the PSD Calculation Option.
  3. Check the pKa's of all the ingredients.
  4. Now make sure you have the correct Solubility Factors (maybe you have low solubility factors).
  5. Now check the solubility corresponding to the Medium pH.
  6. Make sure you have optimized the calibration constant(s) and the 'excipient' constant(s).
  7. Make sure you have your constant pH turned off.
  8. Check your Instrument Speed and Medium Volume.
  9. Try to enter a lower Diffusion Layer Thickness. The default is 30 microns.
  10. If the problem is still unresolved, contact Simulations Plus, Inc.


Question:  My simulation is over-predicted, why?
Answer:  

Did you Optimize the formulation record?  If the simulation is still over-predicted follow the following steps:

  1. Check the physicochemical properties of all the formulation ingredients.
  2. Check the Particle Size Distribution and the PSD Calculation Option.
  3. Check the pKa's of all the ingredients.
  4. Now make sure you have the correct Solubility Factors (maybe you have high solubility factors).
  5. Now check the solubility corresponding to the Medium pH.
  6. Make sure you have optimized the calibration constant(s) and the 'excipient' constant(s).
  7. Make sure you have your constant pH turned off.
  8. Check your Instrument Speed and Medium Volume.
  9. Try to enter a higher Diffusion Layer Thickness. The default is 30 microns.
  10. If the problem is still unresolved, contact Simulations Plus, Inc.




     Simulations Plus, Inc.      42505 10th Street West      Lancaster, CA      93534-7059      USA
     Phone: 661.723.7723      Fax: 661.723.5524      Email: info@simulations-plus.com