Ethyl 4-hydroxybenzoate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics, other

Type of information:

not specified

Remarks:

Publication supporting read-across and providing toxicokinetic data

Adequacy of study:

supporting study

Executive summary:

The in vivo toxicokinetic screening studies consistently showed that Methyl, ethyl and propyl paraben were taken up systemically very rapidly after oral gavage administration to rats and that they were eliminated very rapidly from the bloodstream within one hour after administration. Also, for all test items, the major metabolite p-hydroxybenzoic acid was cleared rapidly from the blood stream within 4–8 h. P-hydroxybenzoic acid does not exhibit systemic toxicity or DART, and it is also not endocrine active.

Reference 2

Endpoint:

basic toxicokinetics, other

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Sep 2019- April 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

The purpose of this study is to obtain information on the pharmacokinetic of Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate and Butyl 4-hydroxybenzoate in rats after oral administration in order to support the read-across approach.

Objective of study:

metabolism

toxicokinetics

Qualifier:

equivalent or similar to guideline

Guideline:

other: See more details under principles of method

Principles of method if other than guideline:

This study was designed as a dose range finding study and in this respect followed the procedures as indicated in the following internationally accepted guidelines and recommendations:
ICH Guideline M3(R2) on non-clinical safety studies for the conduct of human clinical trials and marketing authorisation for pharmaceuticals (EMA/CPMP/ICH/286/1995, December 2009) [1]
CPMP/SWP/1042/99 Rev 1, Guideline on Repeated Dose Toxicity, 18 March 2010 [2]
CPMP/ICH/384/95 Note for Guidance on Toxicokinetics: A Guidance for Assessing Systemic Exposure in Toxicology Studies, June 1995 (ICH S3A) [3]
Procedures and facilities comply with the requirements of Directive 2010/63/EU [4] and the national legislation defined in the animal protection law concerning the protection of animals used for experimental and other scientific procedures [5].

GLP compliance:

no

Radiolabelling:

no

Species:

rat

Details on species / strain selection:

Species/strain: healthy Wistar rats, Crl: WI(Han) (Full Barrier)
Source: Charles River, 97633 Sulzfeld, Germany

Sex:

male/female

Details on test animals or test system and environmental conditions:

Species/strain: healthy Wistar rats, Crl: WI(Han) (Full Barrier)
Source: Charles River, 97633 Sulzfeld, Germany
Sex: male and female; female animals were non-pregnant and nulliparous
Age at the start of the treatment period: approximately 11-12 weeks old
Body weight at the allocation of the
animals to the experimental groups: males: 304 – 431 g (mean: 383.05 g, ± 20% = 306.44 – 459.66 g)
females: 182 – 252 g (mean: 223.70 g, ± 20% = 178.96 – 268.44 g)

- Full barrier in an air-conditioned room
- Temperature: 22 ± 3 °C
- Relative humidity: 55 ± 10%
- Artificial light, sequence being 12 hours light, 12 hours dark
- Air change: 10 x / hour
- Free access to Altromin 1324 maintenance diet for rats and mice
- Free access to tap water, sulphur acidified to a pH of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals)
- The animals were kept in groups of 5 animals / sex / group / cage in IVC cages (type IV, polysulphone cages) on Altromin saw fibre bedding
- Certificates of food, water and bedding are filed for two years at BSL Munich and afterwards archived at Eurofins Munich
- Adequate acclimatization period (at least five days)

Route of administration:

oral: gavage

Vehicle:

other: 1% aqueous hydroxyethyl-cellulose

Remarks:

The vehicle used in this study was 1% hydroxyethyl-cellulose (viscosity 80-125 cP, 2% in water at 20 °C). The aqueous solution was prepared with aqua ad injectionem.

Details on exposure:

The test item, as delivered, was grinded before formulation preparation. Afterwards, test item was weighed into a tared plastic vial on a suitable precision balance and coated with approx. 1/3 of the target volume with 1% aqueous hydroxyethyl-cellulose, the vehicle used in this study.

After producing slurry with the glass rod for 1 min, the rest of the vehicle was added to give the appropriate final concentration. The formulation was then stirred until visual homogeneity is achieved (at least 30 min).
Formulates were kept under magnetic stirring during the administration.

Duration and frequency of treatment / exposure:

In all groups the test item formulations was administered once by gavage. The application volume was 5 mL/kg body weight

Dose / conc.:

1 000 mg/kg bw/day (nominal)

Remarks:

Methy, Ethyl, Propyl and Buty Paraben

Dose / conc.:

500 mg/kg bw/day (nominal)

Remarks:

Methyl, Ethyl. Propyl and Butyl Paraben

No. of animals per sex per dose / concentration:

10 animals per group for each test item and each concentration

Details on study design:

The study was conducted with 2 groups per test item. Animals were treated orally by gavage. Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxy-benzoate or Butyl 4-hydroxybenzoate was administered once. Due to the high number of animals and the sampling time points the dosing and the blood sampling of all test items was not taken place in the same week. Propyl 4-hydroxybenzoate were tested in parallel with Butyl 4-hydroxybenzoate in study week 1 and Methyl 4-hydroxybenzoate were tested in parallel with Ethyl 4-hydroxybenzoate in study week 5. At the end of the test all surviving animals were euthanised.
For pharmacokinetic evaluation after single oral administration, blood was sampled in the week before administration and at different time points following the administration Four time points was investigated per rat. The investigated time points are 5 min, 10 min, 15 min, 30 min, 60 min, 4 h and 8 h after administration.

Statistics:

The findings of this study were evaluated in terms of the observed effects.
All results were reported in tabular form (summarised in mean or summary tables and/or listed in individual data tables).
Toxicology data were captured either on paper according to appropriate SOPs or using the validated computerised system Ascentos® System (version 1.3.4, Pathology Data Systems Ltd.).
Pharmacokinetic parameters were calculated by non-compartmental analysis using the validated software package Phoenix WinNonlin Version 8.1 (Pharsight Corporation, Pittsburgh, USA).
The following parameters were determined from composite plasma concentration time profiles obtained following intravenous or oral administrations to male and female rats on study days 1.
AUC0-t Area under the plasma concentration versus time curve from time zero up to the last quantifiable concentration, calculated by the trapezoidal rule
AUC0-inf Area under the plasma concentration versus time curve from time zero up to infinity with extrapolation of the terminal phase
Clast Last quantifiable concentration or concentration at the last sampling time point
Cmax Observed maximum plasma concentration
SE_AUC0-t Standard error of the area under the mean concentration time curve
SE_Cmax Standard error of data at tmax
tlast Time of last analytically quantifiable plasma concentration or last sampling time point
tmax Time of occurrence of Cmax
t1/2 Terminal half-life
Arithmetic means of concentrations at any individual time point was only calculated if at least 2/3 of the individual data are above the lower limit of quantification (LLOQ) at this specific time point. For the calculation of the mean value the data point below LLOQ was set to zero.
For pharmacokinetic evaluation and plotting of mean concentration time curves all values below LLOQ were set to missing and ignored.

Metabolites identified:

yes

Details on metabolites:

4-Hydroxybenzoic acid

Mean Cmax of 4-Hydroxybenzoic acid were generally observed between 10 and 30 min after dosing of Propyl 4-hydroxybenzoate, Butyl 4-hydroxybenzoate, Methyl 4-hydroxybenzoate or Ethyl 4-hydroxybenzoate with the exception of Butyl 4-hydroxybenzoate after 1000 mg/kg where highest concentrations were observed at the last sampling time point (8 hours). In all treatment groups, individual animals showed 4-Hydroxybenzoic acid concentrations above the BLQ (130 ng/mL) from 10 min until 8 hours after dosing. The highest exposure of 4-Hydroxybenzoic acid was observed in males and females after dosing of Methyl 4-hydroxybenzoate followed by Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate. The highest mean maximum plasma concentration was found in females after dosing of Ethyl 4-hydroxybenzoate followed by Methyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate, and in males after dosing of Methyl 4-hydroxybenzoate followed by Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate. Generally, mean maximum plasma concentrations and overall exposure of 4-Hydroxybenzoic acid increased with increasing dose of the test items. There appeared to be no obvious trend for sex differences in Cmax and AUC0-t after dosing of either test item.

After a single oral administration of 500 or 1000 mg/kg, Propyl 4-hydroxybenzoate, Butyl 4-hydroxybenzoate, Methyl 4-hydroxybenzoate, and Ethyl 4-hydroxybenzoate were rapidly absorbed with mean maximum plasma concentrations observed between 5 and 15 min post dosing. Afterwards, mean concentration-time profiles revealed a multiphasic behaviour with a rapid decline up to 1 hour and a plateau close to the detection limit between 1 and 8 hours. The course of the mean plasma concentrations did not allow extrapolation of the apparent terminal phase and thus, reliable estimation of t1/2 and AUC0-inf was not possible.

Fast decline of all four tested parabens was accompanied by rapid onset of 4-Hydroxybenzoic acid indicating an efficient and comparable metabolism. In fact, 1 h after dosing mean plasma concentrations of all four test compounds had decreased to less than 10% of the maximum concentration. Furthermore, a substantial portion of the overall exposure was seen within the first hour after dosing.

Propyl 4-hydroxybenzoate (Groups 1 and 2): Individual concentrations above the quantification limit (10 ng/mL) were seen for most of the females until 4 hours after dosing of 500 or 1000 mg/kg with detectable concentrations found in 2 animals at the latest sampling time point of 8 hours. In males, for some of the animals plasma levels were BLQ 15 min after dosing already, but others showed detectable plasma concentrations up to 4 hours after dosing at 500 mg/kg and up to 8 hours (1 animal only) after dosing of 1000 mg/kg. In females, mean maximum plasma concentrations (Cmax) and overall exposure (AUC0-t) were lower at the higher dose whereas in males a roughly dose-proportional increase in Cmax and AUC0-t was observed between 500 and 1000 mg/kg. One hour post dosing mean plasma concentrations had already decreased to 2.1 - 8.5% of the mean maximum concentrations and the exposure over the first 1 h

after dosing (AUC0-1h) represents between 25.9 and 63.3% of the overall exposure during the sampling interval (AUC0-t) (in both genders).

Butyl 4-hydroxybenzoate (Groups 3 and 4): Most of the females showed concentrations above the quantification limit (10 ng/mL) until 8 hours after dosing of 500 or 1000 mg/kg. Some of the males had levels BLQ at 1 hour after dosing already but others showed detectable levels until 8 hours after dosing of 500 or 1000 mg/kg. Mean Cmax increased less than dose-proportionally with dose in males and females, and AUC0-t revealed a roughly dose-proportional increase with doses between 500 and 1000 mg/kg with higher mean Cmax and AUC0-t in males than in females. One hour post-dosing mean plasma concentrations were only between 4.3 and 9.1% of the mean maximum concentrations. Further, AUC0-1h was between 42.5 and 54.5% of mean AUC0-t (in both genders).

Methyl 4-hydroxybenzoate (Groups 5 and 6): Individual plasma concentrations of Methyl 4-hydroxybenzoate were all above the quantification limit (10 ng/mL) until 8 hours after dosing. Mean maximum plasma concentrations and overall exposure increased with increasing doses. This increase was less than dose-proportional for Cmax in females and males, roughly dose-proportional for AUC0-t in females, and more than dose-proportional for AUC0-t in males. In general, mean maximum plasma concentrations and overall exposure appeared to be higher in females than in males. Within the first hour after dosing mean plasma concentrations had decreased to 1.6 - 5.1% of the mean maximum concentrations. The exposure over the first 1 h after dosing (AUC0-1h) was between 55.4 and 75.4% of mean AUC0-t(in both genders).

Ethyl 4-hydroxybenzoate (Groups 7 and 8): Individual plasma concentrations of Ethyl 4-hydroxybenzoate were all above the quantification limit (10 ng/mL) until 8 hours after dosing. There was no trend seen for dose-dependency of mean maximum plasma concentrations in females and males, and of AUC0-t in males, whereas in females mean AUC0-t tended to increase dose-proportionally. In general, mean maximum plasma concentrations and overall exposure were higher in females than in males. One hour after dosing mean plasma concentrations had decreased to between 2.0 and 5.9% of the mean maximum concentrations and exposure within the first hour after dosing represents between 50.0 and 70.2% of mean AUC0-t. In females, the mean maximum plasma concentration and overall exposure were highest for Methyl 4-hydroxybenzoate followed by Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate. In males, the highest mean Cmax and AUC0-t were also found for Methyl 4-hydroxybenzoate but followed by Butyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, and Propyl 4-hydroxybenzoate (in both genders).

4-Hydroxybenzoic acid (Groups 1 to 8): Mean Cmax of 4-Hydroxybenzoic acid were generally observed between 10 and 30 min after dosing of Propyl 4-hydroxybenzoate, Butyl 4-hydroxybenzoate, Methyl 4-hydroxybenzoate or Ethyl 4-hydroxybenzoate with the exception of Butyl 4-hydroxybenzoate after 1000 mg/kg where highest concentrations were observed at the last sampling time point (8 hours). In all treatment groups, individual animals showed 4-Hydroxybenzoic acid concentrations above the BLQ (130 ng/mL) from 10 min until 8 hours after dosing. The highest exposure of 4-Hydroxybenzoic acid was observed in males and females after dosing of Methyl 4-hydroxybenzoate followed by Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate. The highest mean maximum plasma concentration was found in females after dosing of Ethyl 4-hydroxybenzoate followed by Methyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate, and in males after dosing of Methyl 4-hydroxybenzoate followed by Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate, and Butyl 4-hydroxybenzoate. Generally, mean maximum plasma concentrations and overall exposure of 4-Hydroxybenzoic acid increased with increasing dose of the test items. There appeared to be no obvious trend for sex differences in Cmax and AUC0-t after dosing of either test item.

Conclusions:

On the basis of this single oral dose toxicity study in rats with Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate and Butyl 4-hydroxybenzoate with male and female Wistar rats with a dose level 500 mg/kg body weight and 1000 mg/kg body weight Including Pharmacokinetic the following conclusions can be made:
The test item was well tolerated by all animals. No mortality or clinical signs of toxicity were observed during the entire study period.
After a single oral administration of 500 or 1000 mg/kg, Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxy-benzoate and Butyl 4-hydroxybenzoatewere rapidly absorbed with mean maximum plasma concentrations observed between 5 and 15 min post dosing. Afterwards, mean concentration-time profiles revealed a multiphasic behaviour with a rapid decline up to 1 hour and a plateau close to the detection limit between 1 and 8 hours. The course of the mean plasma concentrations did not allow extrapolation of the apparent terminal phase and thus, reliable estimation of t1/2 and AUC0-inf was not possible.
Fast decline of all four tested parabens was accompanied by rapid onset of 4-Hydroxybenzoic acid indicating an efficient and comparable metabolism. In fact, 1 h after dosing mean plasma concentrations of all four test compounds had decreased to less than 10% of the maximum concentration. Furthermore, a substantial portion of the overall exposure was seen within the first hour after dosing.

Executive summary:

The purpose of this study was to obtain information on the pharmacokinetic of Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate and Butyl 4-hydroxybenzoate in rats after oral administration.

The study was conducted with 2 groups per test item. Animals were treated orally by gavage once. The 8 groups comprised 10 male and 10 female Wistar rats.

The test item formulation was prepared freshly on the day of administration. The test item was dissolved in 1 % aqueous hydroxyethyl-cellulose, the vehicle used in this study Dose volumes were adjusted individually based on body weight measurement. The following doses were evaluated:

Low Dose: 500 mg/kg body weight High Dose: 1000 mg/kg body weight

The animals were observed precisely during the test period for signs of toxicity. Blood was collected at different time points to investigate the pharmacokinetic. At the end of the test all surviving animals were euthanised.

On the basis of this single oral dose toxicity study in rats with Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxybenzoate and Butyl 4-hydroxybenzoate with male and female Wistar rats with a dose level 500 mg/kg body weight and 1000 mg/kg body weight Including Pharmacokinetic the following conclusions can be made:

The test item was well tolerated by all animals. No mortality or clinical signs of toxicity were observed during the entire study period.

After a single oral administration of 500 or 1000 mg/kg, Methyl 4-hydroxybenzoate, Ethyl 4-hydroxybenzoate, Propyl 4-hydroxy-benzoate and Butyl 4-hydroxybenzoatewere rapidly absorbed with mean maximum plasma concentrations observed between 5 and 15 min post dosing. Afterwards, mean concentration-time profiles revealed a multiphasic behaviour with a rapid decline up to 1 hour and a plateau close to the detection limit between 1 and 8 hours. The course of the mean plasma concentrations did not allow extrapolation of the apparent terminal phase and thus, reliable estimation of t1/2 and AUC0-inf was not possible.

Fast decline of all four tested parabens was accompanied by rapid onset of 4-Hydroxybenzoic acid indicating an efficient and comparable metabolism. In fact, 1 h after dosing mean plasma concentrations of all four test compounds had decreased to less than 10% of the maximum concentration. Furthermore, a substantial portion of the overall exposure was seen within the first hour after dosing.

 

Description of key information

Ethylparaben is rapidly absorbed, metabolised and eliminated predominantly via urine.Ethyl paraben has no bioaccumulative potential.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - dermal (%):

76