Solubility Study Report of Amoxicillin Trihydrate

TABLE OF CONTENTS

1. Table of Contents
2. Introduction
3. Objective
4. Responsibility
5. Information about the Active Pharmaceutical Ingredients
6. Methodology
7. Summary
8. Conclusions

INTRODUCTION

The purpose of this collaborative study is to determine the solubility of amoxicillin trihydrate under different pH conditions. The pH conditions selected are within the extremes of the normal physiological pH of the human gastrointestinal tract.

The solubility of drugs is of major importance in pre-formulation studies of pharmaceutical dosage forms. The solubility improvement allows the drugs to be potential biowaiver candidates and may be a good way to develop more dose-efficient formulations. Solubility studies must be conducted under a physiological range should be between the pH range of 1 - 6.8 at 37 ± 1°C.

The solubility test allows for obtaining the dose: solubility ratio, which corresponds to the ratio between the highest dose available in a pharmaceutical product and the solubility of the drug. Thus, according to FDA guidance, highly soluble drugs exhibit a dose: solubility ratio of less than 250 mL in a pH range of 1 - 6.8 at 37 ± 1°C. According to the BCS, the solubility of drug substances (API) is classified as high solubility or low solubility. The solubility class boundary is based on the highest dose strength of an Immediate Release (IR) product that is the subject of a biowaiver request. A drug substance is considered highly soluble when the highest dose strength is soluble in 250 ml or less of aqueous media over the pH range of 1 - 6.8 at 37 ± 1°C. 

OBJECTIVE

To determine the solubility of amoxicillin trihydrate over the BCS pH range of 1 - 6.8 at 37 ± 1°C according to the Biopharmaceutics Classification Guidance.

RESPONSIBILITY

• It is the responsibility of the Formulation Officer to perform the solubility test as per regulatory guidelines.
• QC Manager should ensure that methods of analysis are available & that the equipment to be used for analysis is properly working & calibrated & chemicals used for analysis are available.
• The Q.A. Manager should ensure that the solubility test is performed and document it.

INFORMATION ABOUT THE API

Amoxicillin trihydrate is a broad-spectrum, beta-lactam antibiotic. It is effective against gram-positive and gram-negative bacteria. Amoxicillin trihydrate is widely used in the treatment and prevention of susceptible infections including upper and lower respiratory tract infections, gonorrhea, oral infections, otitis media, skin and soft tissue infections, urogenital tract infections, biliary tract infections, anthrax, endocarditis prophylaxis, and as a part of the treatment of Helicobacter pylori infection.

Chemical Structure	:
CAS Number	:	61336-70-7
Description	:	It is a white, crystalline powder.
Solubility	:	Slightly soluble in water, very slightly soluble in ethanol (96 %t), and practically insoluble in fatty oils. It dissolves in dilute acids and dilutes solutions of alkali hydroxides.
Molecular Formula	:	C16H19N3O5S,3H2O
Molecular Weight	:	419.4 g/mol
Nature of Drug Substance	:	Trihydrate
Partition Coefficient and pKa	:	It has been noted in the literature that Partition coefficients of amoxicillin trihydrate between isobutanol at 37° C and 0.1M HCl, 0.5M HCl, over the pH range 1 to 3 and over the pH range 7 to 9.5 have been reported as 0.33, 0.66, 0.79, and 0.25, respectively

METHODOLOGY

Equipment

Orbital Flask Shaker	:
Instrument ID & Calibration Date
UV-Visible Spectrophotometer	:
Instrument ID & Calibration Date
pH meter	:
Instrument ID & Calibration Date

Chemicals

Hydrochloric Acid	:	Merck
Sodium Chloride	:	Skylab
Sodium Acetate	:	SDFCL
Glacial Acetic Acid	:	Merck
Sodium Dihydrogen Phosphate	:	SDFCL
Sodium Hydroxide	:	Merck

Glasswares

Measuring Cylinders	:	Calibrated Measuring Cylinders
Beakers	:	Calibrated Beakers
Pipettes	:	Calibrated Pipettes
Other Glasswares	:	Borosil or Equivalent

Documents Used  

Standard operating procedure	:	For operation & calibration of Orbital Flask Shaker, UV-visible Spectrophotometer, pH Meter & Analytical Balance
Calibration documents	:

Working Standard Used: AMOXICILLIN TRIHYDRATE BP

Reference No.	:
LOD	:
Purity (as is basis)	:
Valid up to	:

ALSO READ: Pre-formulation and Formulation Development

Sample Used:   AMOXICILLIN TRIHYDRATE 

Manufactured By	:
Batch Number	:
Manufacturing Date	:
Expiry / Retest Date	:

Method of Analysis

Buffer Solutions:

Preparation of Buffer pH 1.2: Dissolve 2.52 g of sodium chloride in 900 mL of water, adjust the pH to 1.2 with hydrochloric acid (~70 g/L), and dilute to 1000 mL with water.

Preparation of Acetate Buffer pH 4.5: Dissolve 2.99 g of sodium acetate in 900 mL of water, adjust the pH to 4.5 by adding about 14 mL of acetic acid (~120 g/L), and dilute to 1000 mL with water.

Preparation of Phosphate Buffer pH 6.8: Dissolve 6.9 g of sodium dihydrogen phosphate and 0.9 g of sodium hydroxide in 800 mL of water, adjust the pH to 6.8 with sodium hydroxide (~80g/L) and dilute to 1000 mL with water.

Solubility Experiment:

1. Highest therapeutic dose:
2. Recorded temperature (target 37° ± 1 °C):
3. The volume of the buffer:

Standard Preparation (Calibration Curve):

Accurately weigh 60mg of amoxicillin Trihydrate standard and transfer it into a 50ml volumetric flask. Add 30ml pH 1.2 solubility solution to the volumetric flask. Shake the volumetric flask until the complete dissolution of the drug and make up the volume with the remaining quantity of pH 1.2 solubility solution. Dilute 1.5 ml of this solution into a 50 ml volumetric flask.

Similarly, prepare the standard solution in the acetate buffer pH 4.5 and phosphate buffer pH 6.8.

Perform the spectrum of each medium using a UV-visible spectrophotometer and find out the λmax of the drug in each medium.

λmax in pH 1.2:

λmax in pH 4.5:

λmax in pH 6.8:

Saturated solubility Sample Preparation:

To determine the drug's saturated solubility in pH 1.2, pH 4.5, and pH 6.8, take 50 mL of the respective medium in a different conical flask. Add 100mg of sample and observe each medium. Now add an excess amount of amoxicillin Trihydrate in each Conical flask. Check the pH of each solution. Perform the solubility experiment by using an orbital flask shaker for 24 hours at a speed of 50 rpm and the temperature at 37 ± 1 °C. After 24 hours, check the pH of each solution. If necessary, adjust the pH of a solution and run the experiment for one hour. After one hour, filter the resulting samples using filters with 0.45μm pore size filter paper.

Immediately dilute the samples after filtration in order to avoid precipitation of the solute. Measure the absorbance of the drug with a UV Visible Spectrophotometer at the pre-scanned λmax in a particular solubility solvent.

Calculate the solubility in mg/ml using the following formula:

Where;

At = Absorbance of Sample Solution

As = Average Absorbance of standard solution

Ws = Weight of standard

P = Potency of Standard

Calculate Dose : Solubility Volume (DSV) using the following formula:

SUMMARY

CONCLUSION

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ALSO READ: How to Perform Solubility Studies for BCS Classification of Drugs?