2-hydroxy-4-(trifluoromethyl)benzoic acid

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1991

Report date:

1990

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: pharmacokinetics study in SD rats
- Parameters analysed / observed: pharmacokinetic parameters of the test item and its main metabolite in blood plasma.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

3-acetoxy-α,α,α-trifluoro-p-toluic acid

EC Number:

206-297-5

EC Name:

3-acetoxy-α,α,α-trifluoro-p-toluic acid

Cas Number:

322-79-2

Molecular formula:

C10H7F3O4

IUPAC Name:

3-acetoxy-4-(trifluoromethyl)benzoic acid

Test material form:

solid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Triflusal and HTB (2-hydroxy-4-trifluoromethyl benzoic acid) were synthesized at the Synthesis Department of the Research Center of J. Uriach & Co. (Barcelona, Spain).

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Solubility and stability of the test substance in the solvent/vehicle: The test item hydrolyses resulting in HTB. Due to the lack of stability of triflusal in a solution, its degradation during the analytical process was evaluated by preparing concentrations of 100 µg/ml of triflusal in physiological serum, plasma and blood. These solutions were maintained at room temperature and in an ice bath during approximately 3 h. At different times, decrease in triflusal concentration and appearance of HTB were evaluated. At room temperature, triflusal shows a greater degradation in blood, with a hydrolysis of 90.7% at the end of the study. In plasma, hydrolysis was 75.1% and practically non-existent in physiological serum. At a temperature of 4°C, hydrolysis in blood after 170 min decreased to 35.08%. Hydrolysis of triflusal in plasma also descended with this temperature, reaching 25.76% by the end of the study.

Radiolabelling:

no

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 200-250 g

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

7.2 mM of HNaCO3

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The triflusal solution administered was prepared by dissolving 1.25 g of triflusal in 7.2 mM of HNaCO3, pH being adjusted to 7.4.

Doses / concentrations

Dose / conc.:

50 mg/kg bw/day (nominal)

No. of animals per sex per dose / concentration:

5 males per checkpoint

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: according to a crossover design, no further details.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: blood, plasma
- Time and frequency of sampling: Blood samples were drawn by cardiac puncture at the following times: basal, +2.5, +5, +10, +15, +20, +30 min and +1, +2, +4, +8, +12, +18, +24, +36, +48 and +72 h. Plasma was separated from blood by centrifugation at 2000 g for 15 min at 4°C, and EDTA (0.1% final solution) was added as an anticoagulant.
- From how many animals: 5 every time
- Method type(s) for identification: HPLC-UV
- Details on analytical method: The analysis was performed on a Radial-Pak Nova-Pak column (4 µm particle size; 8 nun x 10 cm internal diameter) (Waters Associates); UV detector (275 nm). The mobile phase consisted of methanol dissolved in a 1/20 PIC A solution (55:45). The flow rate was 1 ml/min.
- Validation parameters: The precision, recovery, sensitivity and linearity of the method was studied by adding known amounts of triflusal and HTB to drug-free plasma. The peak retention times were 7.2 min for triflusal and 12.1 min for HTB. No interference between drug-free plasma and endogenous plasma components was observed. Sensitivity may increase when ultraviolet detection is set to 265 om for triflusal and 305 om for HTB. Concentration and peak area were linear for both products within the concentration ranges studied (2.5 to 250 µg/ml) with a correlation coefficient of r =0.99. The results of the precision study for triflusal and HTB are summarized in Table 1 (see 'Any other information on materials and methods incl. tables'). Recovery of HTB was higher than 99% for a concentration range
between 5 and 100 µg/ml. For triflusal the recovery was over 90% for a concentration of 5 µg/ml and over 95% for concentrations above 10 to 100 ug/ml.
- Limits of detection and quantification: The detection limit of this method was 2.5 µg/ml for both products.

Statistics:

All data were fitted to compartmental models using a non-linear Gauss-Newton regression method with the aid of a PCNONLlN program. Pharmacokinetic parameters were calculated according to standard procedures. Statistical significance of the possible differences between the phannacokinetic parameters according to the administration route was calculated by means of a Wilcoxon test. All statistical calculations were carried out using an SPSS/pc program.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The maximum concentration (Cmax) of triflusal in rats after an oral administration was 8.1 ± 2.0 µg/ml reached between 2.5 and 10 min. The absolute bioavailability calculated for triflusal was 10.6%. Triflusal was rapidly hydrolyzed to HTB due to loss of the acetyl group. The maximum concentration (Cmax) of HTB in rats after an oral administration was 237.7 µg/ml and was achieved at 0.7 h.

Details on excretion:

In rats, triflusal was quickly eliminated from plasma with a biological half-life (t ½) of 2.7 min and a clearance (cl) of 73.4 (ml/kg)/min.
The elimination of HTB was much slower with a biological half-life (t ½) of 21.5 h and a clearance (cl) of 5.1 (ml/kg)/h.

Toxicokinetic parameters

Key result

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 21.5 h

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

HTB (2-hydroxy-4-trifluoromethyl benzoic acid)

Any other information on results incl. tables

Table 2. Pharmacokinetic parameters of triflusal after intravenous administration of 50 mg/kg doses in rats. Value of AUC after same oral and intravenous doses.

Parameter
Co	µg/ml	177.9
Ke	l/min	0.261
t½	min	2.66
Vd	ml/kg	281.1
Cl	(ml/kg)/min	73.4
AUC (i.v.)	(µg/ml)/min	720.2
AUC (oral)	(µg/ml)/min	76.4

Table 3. Pharmacokinetic parameters of HTB after intravenous and oral administration of 50 mg/kg of triflusal (equal to 41.5 mg/kg of HTB) in rats.

Parameter		Intravenous admin.	Oral admin.
A1	µg/ml	166.2	279.7
A2	µg/ml	263.5	243.1
Ka	l/h	4.27	8.44
Ke	l/h	0.032	0.028
t½ (Ka)	h	0.162	0.082
t½ (Ke)	h	21.5	24.0
Cmax	µg/ml	252.9	237.7
tmax	h	1.04	0.7
tlag	h	-	0.02
AUC	(µg/ml)/h	8150	8733
Vd	ml/kg	158.1	-
Cl	ml/kg	5.09	-

Comparison of the AUC obtained for the two different administration routes (i.v. vs. oral) can account for the over 100% absorption of HTB.

Applicant's summary and conclusion

Conclusions:

Triflusal was found to hydrolyse rapidly into 2-hydroxy-4-trifluoromethyl benzoic acid in physiological serum, plasma and blood. The elimination of HTB was slower, with a t½ = 2.7 min and a clearance of 73.4 (ml/kg)/min. The maximum concentration (Cmax) of HTB in rats after an oral administration was 237.7 µg/ml and was achieved at 0.7 h. The bioavailability of HTB was determined to be 100%.

Executive summary:

A pharmacokinetic study of triflusal, the parent compound of 2-hydroxy-4-trifluoromethyl benzoic acid (HTB) was performed in rats. Five male Sprague-Dawley rats per group, weighing 200-250 g each, received a single dose of triflusal at 50 mg/kg bw, administered orally by gavage or intravenously by injection into the caudal vein. Blood samples were drawn by cardiac puncture at the following times: basal, +2.5, +5, +10, +15, +20, +30 min and +1, +2, +4, +8, +12, +18, +24, +36, +48 and +72 h. Plasma was separated from blood by centrifugation at 2000 g for 15 min at 4°C, and EDTA (0.1% final solution) was added as an anticoagulant. After adequate preparation, plasma samples were analysed with a validated HPLC-UV method, and the main toxicokinetic parameters for the parent compound and the main metabolite were calculated. In rats, triflusal was quickly eliminated from plasma with a biological half-life (t½) of 2.7 min and a clearance (Cl) of 73.4 (ml/kg)/min. Triflusal was rapidly hydrolyzed to HTB due to loss of the acetyl group. The elimination of HTB was much slower with a t½ of 21.5 h and a Cl of 5.1 (mg/kg)/h. The maximum concentration (Cmax) of triflusal in rats after an oral administration was 8.1 ± 2.0 µg/ml reached between 2.5 and 10 min. The maximum concentration (Cmax) of HTB in rats after an oral administration was 237.7 µg/ml and was achieved at 0.7 h.  The bioavailability of triflusal in rats was only 10.6% while the bioavailability of HTB was more than 100% indicating an important first pass effect.