Phenoxymethylpenicillin potassium

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Remarks:

MainTest

Adequacy of study:

key study

Study period:

17 December 2019 - 30 April 2020

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

EC Publication No. O.J. L142, May 2008

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

April 13, 2004

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name:Pen V Potassium
Lot No.: B519322
Appearance:white, solid powder
Expiry date: 30 April 2024
Storage condition: at room temperature, protected from light

Analytical monitoring:

yes

Remarks:

The analysis of Pen V Potassium was carried out by the previously validated reverse phase HPLC method using UV detection(Study Number: 880-100-4606).

Details on sampling:

The content of Pen V Potassium in the different pH buffer samples was determined at 18 analytical occasions of the test period.Five test samples were analysed at each start of hydrolysis test at each temperature. Two separate tubes with two dilutions each were analysed at each analytical occasion of hydrolysis test solutions and one control tube was taken and analysed as well. The samples were measured after dilution with dilution mixture.The pH of each buffer solution was checked with a calibrated pH meter.

Buffers:

Buffer solution pH 4, 7 and 9:
Sterile buffer solutions of different pH values (pH 4, 7, 9) were prepared using reagent gradechemicals and ultra-pure, sterile water. The required amount was prepared according to the following ratios.

Compositions of the buffer solutions:
pH 4: 2 mL 0.2 M Sodium hydroxide and 250 mL 0.2 M Potassium hydrogen phthalate were diluted to 1000 mL with ultra-pure water.

pH 7: 148 mL 0.2 M Sodium hydroxide and 250 mL 0.2 M Potassium dihydrogen phosphate were diluted to 1000 mL with ultra-pure water.

pH 9: 107 mL 0.2 M Sodium hydroxide and 250 mL 0.2 M Boric acid and Potassium chloride were diluted to 1000 mL with ultra-pure water.

Pen V Potassium concentrations in the buffer solutions were: ~1000 mg/L ≈ 2.5 mM/L.

Details on test conditions:

The test method:Main test
The hydrolysis was examined at pH 4, pH 7 and pH 9 at three different temperatures.Temperature: 15 °C ± 0.5 °C, 37 °C ± 0.5 °C and 50 °C ± 0.5 °C Light and oxygen: The hydrolysis reaction was carried out using a dark thermostat to avoid photolytic effects. Nitrogen was bubbled into the water for five minutes before the preparation of the solutions in order to exclude oxygen. All glassware, water and buffer solutions were sterilised.From each buffer solution containing test item 21 samples of ~25 mL were stored at each temperature in screw-cap glass tubes with PTFE septa. Additionally, 11 control buffer samples were stored at the same temperature.Sterile aqueous buffer solutions at pH 4, 7 and 9 were treated with the test item and incubated in the dark. The decrease of the concentration of the test item was followed over time by analysing the buffer solutions. Sterility confirmation tests were performed at each pH level at the end of the hydrolysis test period. For each temperature at least six data points were taken so that the degrees of hydrolysis are in the range of 10 to 90 %.

Duration:

744 h

pH:

4

Temp.:

15 °C

Initial conc. measured:

ca. 995 mg/L

Remarks:

main test

Duration:

168 h

pH:

4

Temp.:

37 °C

Initial conc. measured:

ca. 991 mg/L

Remarks:

main test

Duration:

38 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

ca. 982 mg/L

Remarks:

main test

Duration:

744 h

pH:

7

Temp.:

15 °C

Initial conc. measured:

ca. 998 mg/L

Remarks:

main test

Duration:

384 h

pH:

7

Temp.:

37 °C

Initial conc. measured:

ca. 985 mg/L

Remarks:

main test

Duration:

216 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

ca. 990

Remarks:

main test

Duration:

600 h

pH:

9

Temp.:

15 °C

Initial conc. measured:

ca. 965 mg/L

Remarks:

main test

Duration:

46 h

pH:

9

Temp.:

37 °C

Initial conc. measured:

ca. 990 mg/L

Remarks:

main test

Duration:

24 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

ca. 1 051

Remarks:

main test

Number of replicates:

6

Positive controls:

no

Negative controls:

no

Preliminary study:

Based on the results of the preliminary test the hydrolysis rate of Pen V Potassium after 5 days at 50 °C was found to be 99 - 82 - 100 % at pH 4, at pH 7 and at pH 9, respectively.

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

Details on hydrolysis and appearance of transformation product(s):

Compared the extracted ion chromatograms and the MRM chromatograms of hydrolysis samples to the corresponding chromatograms of control samples, the following predicted degradation products were observed:
pH4: penilloic acid, penillic acid
pH7: penilloic acid, penicilloic acid, penamaldic acid, isomer of penicilloic acid
pH9: penicilloic acid, penamaldic acid, isomer of penicilloic acid

% Recovery:

ca. 33

pH:

4

Temp.:

15 °C

Duration:

ca. 744 h

% Recovery:

ca. 7

pH:

4

Temp.:

37 °C

Duration:

ca. 168 h

% Recovery:

ca. 21

pH:

4

Temp.:

50 °C

Duration:

38 h

% Recovery:

ca. 35

pH:

7

Temp.:

15 °C

Duration:

744 h

% Recovery:

ca. 11

pH:

7

Temp.:

50 °C

Duration:

216 h

% Recovery:

ca. 4

pH:

7

Temp.:

50 °C

Duration:

216 h

% Recovery:

ca. 16

pH:

9

Temp.:

15

Duration:

600 h

% Recovery:

ca. 11

pH:

9

Temp.:

37 °C

Duration:

ca. 105 h

% Recovery:

ca. 3

pH:

9

Temp.:

50 °C

Duration:

24 h

Key result

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

ca. 24.5

DT50:

ca. 260 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

ca. 23.3

DT50:

ca. 708 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

ca. 30.4

DT50:

ca. 115 h

Type:

(pseudo-)first order (= half-life)

Validity criteria fulfilled:

yes

Conclusions:

The following potential hydrolysis products were identified in stored hydrolysis samples (in buffer solutions pH= 4, 7, 9) using a LC-MS method.

pH 4: penilloic acid, penillic acid

pH 7: penilloic acid, penicilloic acid, penamaldic acid, isomer of penicilloic acid

pH 9: penicilloic acid, penamaldic acid, isomer of penicilloic acid

Executive summary:

The purpose of this study was to evaluate the hydrolysis of Pen V Potassium in different pH buffer solutions and to identify the degradation products of the hydrolysis. The calculated half-life of the hydrolysis reactions at pH 4, pH 7 and pH 9 are calculated to be:

pH value	Temperature °C	t 1/2
		hours	days
4	20	260	11
7		708	29
9		115	4.8

 

Reference 2

Endpoint:

hydrolysis

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source

Justification for type of information:

1. SOFTWARE
Aqueous Hydrolysis Rate Program (HYDROWIN), included in the EpiSuite tool of the US EPA.

2. MODEL (incl. version number)

HYDROWIN v2.00

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
N12C(=O)C(NC(=O)COc3ccccc3)C1SC(C)(C)C2C(=O)O(K)

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
The Aqueous Hydrolysis Rate Program (HYDROWIN) estimates aqueous hydrolysis rate constants for the following chemical classes: esters, carbamates, epoxides, halomethanes, selected alkyl halides and phosphorus esters.  HYDROWIN estimates acid- and base-catalyzed rate constants; with the exception of phosphorus esters, it does NOT estimate neutral hydrolysis rate constants.  The estimated acid- and base-catalyzed rate constants are used to calculate hydrolysis half-lives and selected pHs.  HYDROWIN requires only a chemical structure to make these predictions.  Structures are entered into HYDROWIN by SMILES (Simplified Molecular Input Line Entry System) notations.

Half-Life Estimates:
HYDROWIN estimates a half-life based upon the total base- or acid-catalyzed rate constant.  When a compound contains more than one hydrolyzable group, individually estimated rate constants are summed to yield the total rate constant.  The half-life for base-catalyzed rate constants is calculated at pH 8 from the following equation:
  Half-life  =  0.6931 / (Kb)(1.0E-6)
where 1.0E-6 (or 0.000001) is the OH- concentration in water at pH 8.  A half-life at pH 7 is also reported.  The half-life for acid-catalyzed rate constants is calculated at pH 7 where both the OH- and H+ concentrations are 1.0E-7.
Half-lives at different pHs can be determined simply by moving the half-life decimal point one position right or left for each pH unit change.  For example, if the base-catalyzed half-life at pH 8 is 1.0 day, it will be 10 days at pH 7, 100 days at pH 6, and 0.1 days at pH 9.  If the acid-catalyzed half-life at pH 7 is 1.0 day, it will be 10 days at pH 8, 100 days at pH 9, and 0.1 days at pH 6.

5. APPLICABILITY DOMAIN
The prediction methodology was developed for esters, carbamates, epoxides, halomethanes and alkyl halides.
 
It must be remembered that the overall hydrolysis rate constant is equal to the acid-catalyzed  +  the base-catalyzed  + the neutral hydrolysis rate constants.  If the neutral hydrolysis rate constant is the dominant constant, the acid- or base-catalyzed estimate made by HYDROWIN will not give the true indication of the environmental hydrolysis rate!  
In many instances, the pH of the water will determine which rate constant is dominant.  This situation applies especially to epoxides, halomethanes and alkyl halides.
In addition to predicting hydrolysis rate constants, the version of HYDROWIN identifies a variety of chemical structure classes that hydrolyze and gives relevant experimental data.

6. ADEQUACY OF THE RESULT
The result is adequate for a first assessment of the hydrolysis rate of the substance. An experimental study will follow.

Qualifier:

no guideline followed

Principles of method if other than guideline:

QSAR estimation of the half-life of the test item in water, applying the programme HYDROWIN v2.00 within the EpiSuite tool of the US EPA.

GLP compliance:

no

Specific details on test material used for the study:

N12C(=O)C(NC(=O)COc3ccccc3)C1SC(C)(C)C2C(=O)O(K)

Transformation products:

not measured

pH:

7

Temp.:

25 °C

DT50:

38 000 d

Type:

not specified

Remarks on result:

other: N-Methylacetamide

pH:

8

Temp.:

25 °C

DT50:

3 950 d

Type:

not specified

Remarks on result:

other: Acetamide

Details on results:

HYDROWIN Program (v2.00) Results:
================================
SMILES : N12C(=O)C(NC(=O)COc3ccccc3)C1SC(C)(C)C2C(=O)O(K)
CHEM : Penicillin V Potassium [USAN]
MOL FOR: C16 H17 N2 O5 S1 K1
MOL WT : 388.48
--------------------------- HYDROWIN v2.00 Results ---------------------------
Hydrolyzable Function detected: Amides
-C-C(=O)-N-C
With the exception of a few halogenated acetamides, most amides hydrolyze to acids extremely slowly at 25 degC and pH7 with half-lives measured in centuries. Electronegative groups on carbon or nitrogen greatly accelerate base catalyzed hydrolysis, but alkyl groups on nitrogen retard both acid and base catalyzed processes. No neutral
hydrolysis is evident (Mabey and Mill, 1978).

Selected amides
half-lives include:
Half-Live (in years at 25C, pH7)

Acetamide 3950
Chloroacetamide 1.46
Dichloroacetamide 0.73
Trichloroacetamide 0.23
N-Methylacetamide 38000
Additional experimental amide data are available in the HYDRO on-line
User Guide (help file).

Conclusions:

Half-Live (in years at 25C, pH7)

Acetamide 3950
Chloroacetamide 1.46
Dichloroacetamide 0.73
Trichloroacetamide 0.23
N-Methylacetamide 38000

Description of key information

The hydrolysis rate at 20 °C as a Function of pH of the Penicillin V Potassium was investigated 

Half-Life at pH 4:      11  days  

Half-Life at pH 7:      29  days

Half-Life at pH 9:      4.8 days

Key value for chemical safety assessment

Half-life for hydrolysis:

29 d

at the temperature of:

20 °C