Work on Various Methods Used for the Determination of Acid Neutralizing Capacity of Multifarious Antacid Formulations with Their Comparison

References

[1] Number of times the method was usedor followed in literatures

[2] Prevalence (%) of use of the methods in literatures

[3] pH Meter Method

[4] [7-10, 18, 23-50].

[5] 33

[6] 77

[7] Direct Titration Method

[8] [1,16-17,19]

[9] 4

[10] 9

[11] Back Titration Method

[12] [10, 14,15,20-22]

[13] 6

[14] 14

[15] Next, the authors of the present review work wanted to compare the ANC results obtained by different investigators when they employed different methods for the same antacid formulation. Some representative results were presented in the Table II. It is clear from the Table 2 that the reported three different methods were not used in common to analyze the ANC for the same antacid formulation but at most two of the methods were found to be used todo so. Interestingly, the ANC results reported by the pH meter method as well as by the back titration method were almost identical (Table II). This finding indicated that both the methods have similar accuracy and precision as well as equally acceptable for ANC determination of antacid formulations. However, the reason behind the finding of almost identical results by the mentioned two methods could not be explained until an experiment was done by the author for ANC evaluation of an antacid formulation using the mentioned methods.

[16] TABLE II: Reported ANC, by different method, for the same antacid formulation

[17] Brand Name

[18] Dosage form

[19] Active ingredients

[20] Excipients

[21] ANC by pH

[22] Meter method,

[23] [Ref.]

[24] ANC by back titration method,[Ref.]

[25] ANC by direct titration method,

[26] [Ref.]

[27] Gelusil

[28] Tablet

[29] Aluminum hydroxide (250 mg), Magnesium hydroxide (300 mg)

[30] Dimethicone, Mg and Al silicate

[31] 23.19 ± 0.06

[32] mEq/g, [10]

[33] 23.21 ± 0.27

[34] mEq/g, [10]

[35] NA*

[36] Ulgel

[37] Tablet

[38] Aluminum hydroxide (200 mg), Magnesium hydroxide (200 mg)

[39] Simethicone

[40] 23.96 ± 0.09

[41] mEq/g, [10]

[42] 23.91 ± 0.11

[43] mEq/g, [10]

[44] NA*

[45] Digene

[46] Suspension

[47] Aluminum hydroxide (830 mg), Magnesium hydroxide (185 mg)

[48] Simethicone

[49] 20.96 ± 0.09

[50] mEq/5mL, [10]

[51] 20.79 ± 0.06

[52] mEq/5mL,[10]

[53] NA*

[54] Diovol

[55] Suspension

[56] Aluminum hydroxide (300 mg), Magnesium hydroxide (250 mg)

[57] Dimethicone

[58] 26.28 ± 0.05

[59] mEq/5mL, [10]

[60] 26.17 ± 0.18

[61] mEq/5mL, [10]

[62] NA*

[63] Entacyd plus

[64] Tablet

[65] Dried aluminum hydroxide(425 mg), Magnesium hydroxide(400 mg)

[66] Simethicone 30 mg

[67] NA*

[68] NA*

[69] 2ml 0.1N HCl/ tablet, [1]

[70] Maganta plus

[71] Tablet

[72] Magaldrate 480 mg

[73] Simethicone 20 mg

[74] NA*

[75] NA*

[76] 1 ml 0.1N HCl/ tablet, [1]

[77] NA= Not Applicable, Ref.= Reference

[78] Finally, authors of the present review work performed a comparative study with the same antacid tablets of same batch using the three different reported methods in order to see the relative accuracy and precision of the results obtains by the mentioned three reported methods. The Hanna pH meter (pH 300, Portugal) was used to evaluate the ANC value in pH meter method. In the experiments, the antacyd plus tablet of Square pharma having MA No of 012-258-007 was used. The obtained results were tabulated in the Table III. In case of pH meter method, 11.26 mL/g, 10.94mL/g, and 10.62 mL/g of 0.5 N NaOH wererequired to reach pH 3.5 in titrating the three test solutions of antacid formulation. The ANC values were calculated using the eq-1for the respective above mentioned three solutions and the results were 24.37 mEq/g, 24.53 mEq/g, and 24.69 mEq/g, respectively.It was found that the average ANC of the antacyd plus tablets in pH meter method was 24,53 mEq/g.In the back titration method,13.42 mL/g, 13.28 mL/g, 13.56 mL/gof 0.5 N NaOH were required for titrating the three solutions of antacid formulation and to change the colour of indicator.The ANC values of the three respective antacid solutions were calculated as 23.29 mEq/g, 23.36 mEq/g, 23.56 mEq/g. The average ANC value for back titration method was 23.29 mEq/g. And the findings (average ANC values 24.53 mEq/g in pH meter method, and 23.29 mEq/g in back titration method) resonated the similarity of ANC results observed by the other authors in pH meter method, and back titration method, respectively (Table-2).It was so because pH meter method and the back titration methods were essentially same except in the back titration method, an external indicator was used while in the pH meter method the electrode response was used to end the titration. On the other hand, only 1.7 mL 0.1 N HCl was neutralized per antacyd plus tablet in direct titration method (Table II). Similar results were also reported by Jakariaet al.[1] in 2015 (Table 3). Now, if one converts the direct titration method results for example 1.7 mL 0.1 N HCl to mEq/g for the sake of comparison then it appears as (1.7 x 10-3 L x 0.1 mEq x1000/L=) or 0.14 mEq/g, which is too low compared to the other methods (Table-III) and also out of compliance with the FDA and USP specifications. It is not acceptable as well as not explainable to the authors of the present work. Anyway, out of the three methods employed for ANC determination

[79] TABLE III: Results of ANC values obtained by different method for the sameantacid tablets of the same batch

[80] Methods of Analysis

[81] Brand Name, Manufacturer of the tablet

[82] Contents of the Tablet

[83] ANC Results

[84] pH meter method

[85] Antacyd plus tablet, Square Pharma, Bangladesh

[86] Dried aluminum hydroxide gel(400 mg), Magnesium hydroxide(400 mg), Simethicone 30 mg

[87] a24.53 mEq/g

[88] b24.62 mEq/g

[89] Back titration method

[90] Do

[91] Do

[92] 23.29 mEq/g

[93] Direct titration method

[94] Do

[95] Do

[96] 1.7 ml 0.1N HCl /tablet [1] Equivalent to 0.14mEq/g (converted by the authors of this work)

[97] a = ANC values as per calculation by the reported formula (eq. 1); b = ANC values as per calculation by the formula used in the local pharmaceutical company (eq. 3)

[98] The formula reported by the literature was supposed to results in different ANC values for tablet to tablet as the weight of one tablet (1.212 g) differed from the weight of the other tablet (1.166 g) of the same batch. Therefore, the authors wanted to know what formula is used in the QC of the local pharmaceutical companies. Upon personal communication, it was found that one of the leading company uses the following formula for the calculation of ANC value (mEq) in case of pH meter method:

[99] V1*1*F1- (V2*0.5*F2)Wu*Rw ………………………….. (3)

[100] Here,

[101] V1 = Volume of 1 N HCl

[102] F1 = Factor of 1 N HCl

[103] V2 = Volume of 0.5 N NaOH

[104] F2 = Factor of 0.5 N NaOH

[105] Wu = Weight of the sample in mg

[106] Rw = Average weight of a tablet in mg.

[107] It seemed to the authors of the present work that afore mentioned formula (eq. 3) is more acceptable as it considered the weightage of the tablet weight in the formula. However, the obtained result (24.62 mEq/g) was not differed much (Table-3) with the results calculated using the reported formula (eq.1).Note that, the local pharmaceutical company that was mentioned earlier by the authors of this work does not use the back titration method. As a result, the authors could not report ANC values (two results) for back titration method as like that of the pH meter method in the Table-3.

[108] Potential sources of error or precision for pH meter method are:

[109] Selection of pH meter (it needs a pH meter of high precision).

[110] The addition process of acid to the antacid solution to make pH 3.5. From the present experimental study, it is recommended to add minute amount of acid slowly each time.

[111] Error may be introduced during the solution preparation procedures of 1 N HCl and 0.5 NaOH. They need to be standardized properly.

[112] Potential sources of error or precision for back titration method are:

[113] Selection of indicator and the amount of it added to the antacid solution.

[114] Observation of color change of the indicator at the end point of titration.

[115] Potential sources of error or precision for direct titration method:

[116] Selection of pH meter (it needs a pH meter of high precision).

[117] Addition technique of acid (acid has to be added drop wise very carefully so that pH does not change abruptly).

[118] Authors of the present work compiled the standard specifications for ANC (Table-IV) established by the different organizations contributing to the pharmacy fields. It appeared from the Table-IV that the standard specification values varied slightly and tolerably between FDA and USP for the solid dosage form andthere was no specification for liquid dosage form in FDA and BP. Next, the authors of the present work compared ANC result for an antacid formulation assessed by the authors to the reported standard specifications (Table-IV). The findings (Table-III) of the authors of the present work as well as the reported ANC values (Table-II) of the other authors complied with the specifications of ANC (Table-IV) only because the standard specifications were set to one ended value like greater than or not less than a certain value (Table-IV). The authors felt that ANC values should have a range otherwise for example: the specification ≥ 5 mEq/dose may comply with ANC 50 mEq/dose or even with ANC 500 mEq/dose and so on. Likewise, not less than 7 or 9 mEq/dose specification may comply with for example ANC 40 mEq/dose or even ANC 800 mEq/dose and so on, which is not logical and scientific.

[119] TABLE IV – The standard ANC specifications set by the different relevant organizations

[120] Organization

[121] ANC value mentioned

[122] FDA

[123] ≥ 5 mEq/dose

[124] USP

[125] Not less than 7 mEq per dose of tablet preparation

[126] Not less than 9 mEq per dose of liquid preparation

[127] BP

[128] No specification for solid as well as liquid dosage forms

[129] The authors of the present review work found from their experimental study that the pH meter method has some advantages over back titration method such as the pH meter method is more precise, cost-effective, easy to carry out, and less time consuming. Similarly, pH meter method is more precise than direct titration method. In addition, pH meter method is the authorized method by USP while remaining two other methods are not any pharmacopoeia or organization like FDA, ICH etc. adopted method. All these factors might have led the pH meter method to be the favored method to the most of the investigators and it to appear as the topmost used method (Table-I) for ANC evaluation of antacid formulations.

[130] CONCLUSION

[131] As per the present literature review, three methods viz. pH-meter method, back titration method and direct titration method were found to use for the ANC evaluation of antacid formulations. Prevalence of use of the methods in the literatures was 77 %for pH meter method, 14 % for back titration method, and 9 % for direct titration method. Among the reported methods, pH meter method was used by most of the investigators (77 %) working in this field even though the pH meter method and the back titration method resulted in almost identical ANC values for the same antacid formulation. The authors of the present review work found from their experimental study that the pH meter method has some advantages over back titration method such as it is a pharmacopoeia adopted method, more precise, does not use extra chemicals like indicator (so cost effective), less time consuming and easy to carry out with fewer steps in the titration process. Similarly, the pH meter method is found to be superior than the direct titration method because pH meter method is a pharmacopoeia adopted, and more precise method. It is important to investigate why the direct titration method results in too low ANC value compared to the other methods. Pharmacopoeia methods are usually validated. So, back titration and direct titration methods are recommended for validation.

[132] It appeared that the standard specification for ANC values was mentioned in the literatures but as greater than or less than of certain values which are very vague and confusing. And hence it (specification of ANC value) needs to be established as a range.

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@article{1704936,
      author = {Mossammat Rima Akter, Md. Saddam Hossain, Shomrat Saikh, Md. Nur Alam, Md Rafiquzzaman},
      title = {Work on Various Methods Used for the Determination of Acid Neutralizing Capacity of Multifarious Antacid Formulations with Their Comparison},
      journal = {Iconic Research And Engineering Journals},
      year = {2023},
      volume = {7},
      number = {4},
      pages = {434-445},
      issn = {2456-8880},
      url = {https://www.irejournals.com/formatedpaper/1704936.pdf},
      abstract = {Acidity is a condition which may be defined as heart burn, formation of gas in stomach due to excess production of stomach acid. Antacids, among other medications, are widely used medicines to reduce the incommodious symptoms of acidity through neutralizing the excess stomach acid. The potency of antacid formulations depends on the Acid Neutralizing Capacity (ANC). However, there is no review work on the methods used for the determination of acid neutralizing capacity of antacid formulations. Therefore, the objectives of the present study are to find out different methods through literature review used for the determination of acid neutralizing capacity of antacid formulations, compare them from different perspectives, and to compile the reported standard specifications for ANC. Besides, another objective is to employ the reported methods to evaluate acid neutralization capacity of an antacid tablet formulation. Reviewed articles include three reported methods viz. pH meter method, back titration method and direct titration method for ANC value determination. The authors of the present review work found from their own experimental study that the pH meter method has some advantages over back titration method such as the pH meter method is cost-effective, easy to carry out, and less time consuming.},
      keywords = {Acid Neutralizing Capacity, Antacids, Ph Meter Method, Direct Titration Method, Back Titration Method.},
      month = {October},
  }