Mechanochemical Activation of Olanzapine in Mixed Solid Dispersions: Impact of Excipients on Release and Permeation Rates

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presents the obtaining and the characterization of binary and ternary solid dispersions (SDs) of olanzapine (OLZ) with several excipients. The obtained two- and three-component systems were thoroughly investigated by means of DSC, PXRD, FTIR, Raman and SEM methods and the dissolution and permeation rate of the drug substance upon its release from SDs was quantitatively characterized. The authors conducted an interesting study; the results of the study could be useful for pharmacists, medicinal chemistry specialists and drug formulation scientist working in drug formulation development. The manuscript is carefully conceived; serious experimental work was performed. There are some points that the authors should address before accepting the manuscript for publication:      

1. All the acronyms used have to be fully given when they first appear, both in the Abstract and in the body of the text (e.g. PXRD, FTIR, DSC, SEM in the abstract; GI in line 32; BCS in line 81; PXRD, FTIR, DSC, SEM. In line 93.. )
2. Lines 111-112: The authors stated ”GABA....manifest antihypotensive and diuretic effects”. This should be „manifest hypotensive/antihypertensive and diuretic effects”
3. In lines 277-278 authors concluded ” FTIR analysis revealed no evidence of interactions between the components in any of the binary solid systems studied”. But, in Section S4, authors pointed out the disappearance of OLZ characteristic bands at 3239 cm^-1, 2929 cm^-1, and 1287 cm^-1 from the spectra of both OLZ/SBE-β-CD pm and SD. In my opinion, the absence of OLZ bands can be considered an evidence of an interaction between the drug substance and cyclodextrin, as it is observed in both the pm and the DS.
4. The Raman spectra of three-component pm are missing from Fig 2. They should be presented.
5. In lines 284-285 the authors stated: „ Analysis of the results suggested the shift of the OLZ band from 1580 cm^-1 to 1691 cm^-1 in the OLZ/SBE-β-CD (1:1)-SD” As the Fig 2c shows the OLZ band shifts from 1580 cm^-1 to 1591 cm^-1 (not 1691), please review this.
6. In lines 407-408 the authors classified the systems according to crystallinity without including OLZ/SBE-β-CD/GABA (1:0.75:0.25) SD. This last system should also be included in the ranking.
7. In lines 440-441 the authors stated ”the cumulative release after 420 min (the end of the experiment) was 73% for raw OLZ and 57.5% for ground OLZ”. According to Fig 4a, the release of ground OLZ after 420 min is around 70%, very closed to OLZ raw, please check it out.

Author Response

Dear Reviewer, we sincerely appreciated your comments concerning our manuscript which

are valuable and helpful for its revising and improving. We have addressed all the comments. The corrections and additions are marked in red.

 

Comment:

1. All the acronyms used have to be fully given when they first appear, both in the Abstract and in the body of the text (e.g. PXRD, FTIR, DSC, SEM in the abstract; GI in line 32; BCS in line 81; PXRD, FTIR, DSC, SEM. In line 93.. )

Reply:

We gave all full names of the acronyms used at first mentioning in the manuscript.

 

Comment:

2. Lines 111-112: The authors stated ”GABA....manifest antihypotensive and diuretic effects”. This should be „manifest hypotensive/antihypertensive and diuretic effects”

Reply:

The mistake has been corrected.

 

Comment:

3. In lines 277-278 authors concluded ” FTIR analysis revealed no evidence of interactions between the components in any of the binary solid systems studied”. But, in Section S4, authors pointed out the disappearance of OLZ characteristic bands at 3239 cm^-1, 2929 cm^-1, and 1287 cm^-1from the spectra of both OLZ/SBE-β-CD pm and SD. In my opinion, the absence of OLZ bands can be considered an evidence of an interaction between the drug substance and cyclodextrin, as it is observed in both the pm and the DS.

Reply:

Dear Reviewer, thank you for this valuable comment. We agree that the absence of OLZ bands in the physical mixture and solid dispersion of OLZ/SBE-β-CD could indicate an interaction. However, upon closer inspection, it is evident that the specified characteristic bands of OLZ have a significantly lower intensity compared to the characteristic bands of SBE-β-CD located within a few wavenumbers, and therefore cannot be visualized and do not confirm an interaction between the components of the SD. The corresponding text has been included in Section S4.

 

Comment:

4. The Raman spectra of three-component pm are missing from Fig 2. They should be presented.

Reply:

Raman spectra of the three-component physical mixtures were not recorded, as the analysis of the PXRD, FTIR, and DSC experiments showed that the main changes in the studied systems with excipients occur specifically during grinding.

 

Comment:

5. In lines 284-285 the authors stated: „ Analysis of the results suggested the shift of the OLZ band from 1580 cm^-1to 1691 cm^-1in the OLZ/SBE-β-CD (1:1)-SD” As the Fig 2c shows the OLZ band shifts from 1580 cm^-1 to 1591 cm^-1 (not 1691), please review this.

Reply:

Dear Reviewer, we apologize for our oversight. The text has been corrected to "… the shift of the OLZ band from 1580 cm^-1 to 1591 cm^-1 in the OLZ/SBE-β-CD (1:1)-SD "

 

 

 

Comment:

6. In lines 407-408 the authors classified the systems according to crystallinity without including OLZ/SBE-β-CD/GABA (1:0.75:0.25) SD. This last system should also be included in the ranking.

Reply:

The OLZ/SBE-β-CD/GABA (1:0.75:0.25) SD has been included in the crystallinity ranking.

 

Comment:

7. In lines 440-441 the authors stated ”the cumulative release after 420 min (the end of the experiment) was 73% for raw OLZ and 57.5% for ground OLZ”. According to Fig 4a, the release of ground OLZ after 420 min is around 70%, very closed to OLZ raw, please check it out.

Reply:

Thank you very much for your comment. The text has been corrected according to Fig 4a.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Comments to the Authors

This study aimed study the dissolution/release and permeation of olanzapine (OLZ) from two- and three-component solid dispersions (SDs) with sulfobutylether-β-cyclodextrin (SBE-β-CD) and several pharmaceutical adjuvants as solubilizing agents. Performance of the formulation was evaluated by means of in vitro studies. Following issues should be considered by the authors.

Major comments

• Intestinal membrane is a complex biological barrier and express variety of drug transporters and enzymes. What is the rationale for using artificial membrane to evaluate the permeation properties of the developed solid dispersions, considering that Intestinal cell lines such as Caco-2 cells could provide more physiologically relevant data regarding in vivo absorption and permeability?
• Dissolution studies were conducted only at pH 7.4; however, for orally administered dosage forms, evaluation in physiological media (e.g. 0.1 N HCl, pH 4.5, and pH 6.8) is generally recommended to better assess the dissolution performance of the formulation.
• The manuscript lacks information about the analytical method used and its validation parameters. Therefore, Information concerning the analytical method  and its validation should be included.
• The Results and Discussion section is largely focused on presenting the results. Therefore, a comparative analysis of the results with relevant literature should be added to strengthen the Results and Discussion section.

2.4.Dissolution measurements and calculation of quantitative parameters:

• Amount of SD complex used for the dissolution study
• Stability of olanzapine during the dissolution study
• Maintenance of sink condition
• Please specify the number of data points used for the f₂ similarity analysis and report the RSD values at both the initial and later sampling time points
• Line 170: Please clarify the purpose of using a sheet of aluminum foil instead of the membrane

2.5. Permeation experiments:

• Amount of SD complex added to the donor compartment
• Potential for interaction between dialysis membrane and olanzapine
• Volumes of the donor and acceptor compartments.
• Maintenance of sink condition
• Stability of olanzapine during the permeation experiments

Minor comment:

Lines 121-122: reference should be provided for “This compound is approved by the FDA 121 for use in the treatment of acute bleeding caused by elevated fibrinolytic activity”

Author Response

Dear Reviewer, we sincerely appreciated your comments concerning our manuscript which are valuable and helpful for its revising and improving. We have addressed all the comments. The corrections and additions are marked in red.

 

Comment:

• Intestinal membrane is a complex biological barrier and express variety of drug transporters and enzymes. What is the rationale for using artificial membrane to evaluate the permeation properties of the developed solid dispersions, considering that Intestinal cell lines such as Caco-2 cells could provide more physiologically relevant data regarding in vivo absorption and permeability?

Reply:

We accept that Intestinal cell lines such as Caco-2 cells could provide more physiologically relevant data regarding in vivo absorption and permeability. However, as noted in the literature (Nothnagel and Wacker, 2018. https://doi.org/10.1016/j.ejps.2018.05.004. Benavente, 1984. https://doi.org/10.1515/jnet.1984.9.3.217. Wu et al. 2019. https://doi.org/10.1016/j.ejps.2019.105026.), the regenerated cellulose barrier serves as the  standard, simpler  and  cheaper  barrier  often utilized for  the transport  study and  for  the  sake of comparison between different drug formulations containing a drug compound and excipients. It is highly permeable to small molecules, the drug diffusion rate through the barrier is highly controlled by the drug concentration gradient between the both sides of the barrier. Chaitanya Mannava et al. (Chaitanya Mannava et al., 2023. https://doi.org/10.1021/acs.molpharmaceut.3c00159) stressed that "the measurement of higher flux and diffusion of a drug through a semipermeable membrane in in vitro experiments is the first sign of anticipating high drug permeability in in vivo setting".

The rationale for using the regenerated cellulose membrane has been described in the manuscript (Section 2.5. Permeation experiments) and supported by the appropriate references.

 

Comment:

• Dissolution studies were conducted only at pH 7.4; however, for orally administered dosage forms, evaluation in physiological media (e.g. 0.1 N HCl, pH 4.5, and pH 6.8) is generally recommended to better assess the dissolution performance of the formulation.

Reply:

We fully agree with the reviewer that for orally administered dosage forms, evaluation in physiological media (e.g. 0.1 N HCl, pH 4.5, and pH 6.8) is generally recommended. The dissolution medium, buffer pH 7.4, was selected for the following reasons.

1. As shown in the literature, olanzapine is a weak base with a pK_a of 7.22 (Akula and Lakshmi, 2018. https://doi.org/10.1590/s2175-97902018000200070). We previously determined the solubility of olanzapine and found it to be 28-fold higher in a buffer at pH 2.0 than at pH 7.4 (Volkova et al., 2026. https://doi.org/10.1016/j.colsurfa.2025.138728.). According to the calculated ionization profile, the solubility of the compound decreases as the pH of the dissolution medium increases. Buffer at pH 7.4 was therefore chosen to predict the dissolution rate in a physiological medium, corresponding to the minimum solubility.
2. Since the aim of this work was to investigate the effect of mechanochemical activation of olanzapine, both in the presence and absence of one or more excipients, on its dissolution rate and membrane diffusion, a medium with minimal solubility was preferable to achieve the maximum observable effect.
3. In accordance with the recommendations reported in the literature [Youdim et al., 2003. https://doi.org/10.1016/S1359-6446(03)02873-3.] - "the ideal intestinal in vitro permeability assay would have pH 6.0 and 7.4 in the donor wells, with pH 7.4 in the receiver wells" - buffer pH 7.4 was used.

We have included a brief rationale for the selected pH in the manuscript (in the description of the study objective within the Introduction).

 

Comment:

• The manuscript lacks information about the analytical method used and its validation parameters. Therefore, Information concerning the analytical method and its validation should be included.

Reply:

We thank the reviewer for this valuable comment. A detailed description of the analytical method, including its validation parameters, has now been added to the revised manuscript (Materials and Methods, Section 2.4. Dissolution measurements and calculation of quantitative parameters).

 

Comment:

• The Results and Discussion section is largely focused on presenting the results. Therefore, a comparative analysis of the results with relevant literature should be added to strengthen the Results and Discussion section.

Reply:

A comparative analysis of the results with relevant literature has been added to the Results and Discussion section (sections 3.1.2. Surface morphology characterization by SEM, 3.2. In vitro dissolution/release and diffusion through the membrane of OLZ SDs ).

 

2.4.Dissolution measurements and calculation of quantitative parameters:

 

Comment:

• Amount of SD complex used for the dissolution study

Reply:

The amount of SD was calculated separately for each sample based on the amount of OLZ equal to 0.56 mg in 7 mL. The corresponding text has been added to the manuscript (2.4. Dissolution measurements and calculation of quantitative parameters).

 

Comment:

• Stability of olanzapine during the dissolution study

Reply:

Stability of olanzapine during the dissolution study was checked by PXRD. The results are illustrated in Figure S2e.

The description of the changes after the dissolution has been provided in Section S3.

 

Comment:

• Maintenance of sink condition

Reply:

Dissolution experiments were conducted under nonsink conditions according to the procedure described in the literature (Salas-Zúñiga et al. Pharmaceutics. 2019, 12, 23. https://doi.org/10.3390/pharmaceutics12010023.). Under nonsink conditions, the results more accurately predict the in vivo behavior of drugs where dissolution is limited by solubility. This is ideal for testing amorphous solid dispersions and discriminating between formulations.

Additional text has been introduced in the manuscript (Section 2.4. Dissolution measurements and calculation of quantitative parameters).

Comment:

• Please specify the number of data points used for the f₂ similarity analysis and report the RSD values at both the initial and later sampling time points

Reply:

All experimental points (13 points) were used for the f₂ similarity analysis. The RSD values for the 20 min (initial period) and 360 min (final period) time points were 3.21% and 3.19%, respectively. The corresponding text has been added to the manuscript (3.2. In vitro dissolution/release and diffusion through the membrane of OLZ SDs).

 

Comment:

• Line 170: Please clarify the purpose of using a sheet of aluminum foil instead of the membrane

Reply:

This dissolution setup was recommended by Sironi et al. (Eur. J. Pharm. Sci. 2017, https://doi.org/10.1016/j.ejps.2016.09.001.) to avoid the effect of changes in the donor concentration due to sampling and replacement with fresh buffer on permeability.

The explanation has been provided (Section 2.4. Dissolution measurements and calculation of quantitative parameters).

 

2.5. Permeation experiments:

Comment:

• Amount of SD complex added to the donor compartment

Reply:

Amount of SD complex added to the donor compartment in permeation tests was the same as for the respective dissolution experiment. The corresponding text has been added to the manuscript (2.5. Permeation experiments).

 

Comment:

• Potential for interaction between dialysis membrane and olanzapine

Reply:

Among others, the hydrophilic membranes based on the regenerated cellulose have been intensively used for the purposes of the comparison of the permeability between various drug compositions. As it was reported [Berben et al. Eur. J. Pharm. Sci. 2018, 119, 219–233.], a cellulose membrane with a molecular cutoff weight of 12–14 kDa is regularly performed to estimate the accessible drug fraction. Being applicable for diffusion rate evaluations, this barrier is hydrophilic, capable of water permeation, and cannot simulate the lipophilic layer of cell membranes.

The drug diffusion rate through dialysis membrane is highly controlled by the drug concentration gradient between the both sides of the barrier [Wu et al. Eur. J. Pharm. Sci.  2019, https://doi.org/10.1016/j.ejps.2019.105026. Nothnagel and Wacker, Eur. J. Pharm. Sci, 2018, https://doi.org/10.1016/j.ejps.2018.05.004.]. Cellulose membrane functions effectively in oral controlled-release applications. As it was reported, artificial cellulose membrane is a  convenient relatively inexpensive tool for the fast permeability screening in the  case of using  the excipients as solubilizing agents [Berben et al. Eur. J. Pharm. Sci. 2018, 119, 219–233.]. 

We found no literature evidence of interaction between the cellulose membrane and olanzapine or other drug compounds. Given the hydrophilic nature of the membrane and the lipophilicity of olanzapine, it is highly likely that no interaction occurs.

 

The rationale of using the cellulose membrane has been added to the manuscript (2.5. Permeation experiments).

 

 

Comment:

• Volumes of the donor and acceptor compartments.

Reply:

The volumes of the donor and acceptor compartments were 7 mL/7 mL. This information has been added in Section 2.4. Dissolution measurements and calculation of quantitative parameters

 

Comment:

• Maintenance of sink condition

Reply:

The permeation experiments meet the sink conditions when the maximum solution concentration in the receiver cell was less than one-third of the crystalline solubility (Raina et al. J. Pharm. Sci. 2014, https://doi.org/ 10.1002/jps.23826.).

This information has been added in Section 2.5. Permeation experiments.

 

Comment:

• Stability of olanzapine during the permeation experiments

Reply:

Since interaction between the dialysis membrane and olanzapine is unlikely, the state of olanzapine after passing through the membrane will be the same as upon dissolution.

 

Comment:

Lines 121-122: reference should be provided for “This compound is approved by the FDA 121 for use in the treatment of acute bleeding caused by elevated fibrinolytic activity”

 

Reply:

The appropriate reference has been provided.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have provided satisfactory responses to all my comments. Therefore,  I have no additional comments.