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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1996-1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: published and peer-reviewed publication, with many experimental details

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1997
Report Date:
1997

Materials and methods

Objective of study:
excretion
metabolism
other: plasma kinetics
Test guideline
Guideline:
other: none
Principles of method if other than guideline:
The metabolism and toxicity of dapsone was compared in-vitro and in-vivo in rat, mouse and man. Metabolism was assessed by high-pressure liquid chromatography-mass spectrometry and methemoglobin formation has been used as a toxic endpoint.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Dapsone, 3,3'-diaminodiphenyl sulfone was from Sigma Chemical Co. Ltd. (Poole, UK).
4-Amino-4'-nitrodiphenylsulfone was prepared by the method of Raiziss et al. (1939) and reduced with a palladium-carbon catalyst (Entwistle et
al., 1978) to yield dapsone hydroxylamine, which was found to be pure by thin layer chromatography and HPLC and the structure was confirmed by mass spectrometry and nuclear magnetic resonance.
Radiolabelling:
yes
Remarks:
14C-Dapsone100 mmol, 3 mCi100 mmol, 3 mCi

Test animals

Species:
other: mouse, rat, Humans
Sex:
male/female
Details on test animals and environmental conditions:
RATS : male and female Wistar rats
MICE : CD1 mice
HUMANS : 5 male volunteers (65-93kg)

Administration / exposure

Route of administration:
other: via carotide artery for metabolism and excretion analyses, not specified for others.
Vehicle:
DMSO
Remarks:
1ml/kg
Details on exposure:
- Toxicity and plasma kinetics of dapsone in the rat and mouse :
Dapsone (100 µmol/kg) in DMSO (1 ml/kg i.p.) was administered to male (200–280 g, n=6) and female Wistar rats (200–230 g, n=4) or male CD1 mice (52–64 g, groups of n=4).

- Metabolism and excretion of [14C]dapsone in the rat :
[14C] Dapsone (100 µmol, 3 µCi) in DMSO (1ml/kg) was administered to male (n= 8) or female (n= 6) Wistar rats (200–280 g) via the carotid artery.

- Metabolism and excretion of [14C]dapsone in the mouse :
[14C] Dapsone (100 µmol, 3 µCi) in DMSO (1ml/kg) was administered to male (n= 8) CD1 mice (20–25 g) via the carotid artery.

- Toxicity and plasma kinetics of dapsone in humans :
a single dose (100 mg) of dapsone were determined in five male volunteers (65–93 kg)

- Metabolism and toxicity of dapsone and dapsone hydroxylamine in vitro :
Microsomal fractions were prepared from the pooled livers of male and female rats (n = 6), male mice (n = 6) or from six individual human livers.
Dapsone (100 µM) was incubated with microsomes (1 mg of protein) and 1 mM NADPH (omitted from controls) in the presence of washed human erythrocytes (500 ml of a 50% suspension) in HEPES-buffered saline (1 ml) at 37°C and the methemoglobin content assessed after 1 h.
For the metabolism studies, either dapsone or dapsone hydroxylamine (100 µM) were incubated with microsomes (1 mg of protein) and 1 mM NADPH in the presence of 500 µM ascorbate.
Duration and frequency of treatment / exposure:
single application
Doses / concentrations
Remarks:
Doses / Concentrations:
100 micro-mol per kg
No. of animals per sex per dose:
4 to 8
Control animals:
no
Positive control:
one
Details on dosing and sampling:
- Toxicity and plasma kinetics of dapsone in the rat and mouse :
Blood samples (400 µl), obtained from the tail arteries of rats under diethyl ether anesthesia or from one group of mice via the brachial artery, were taken at 0, 1, 2, 3, 5, 8 and 24 h after dosing. Blood (100 µl) was assayed immediately for methemoglobin content (Harrison and Jollow, 1986). Plasma was prepared by centrifugation (3000 xg, 5 min) and an aliquot (100 µl) was spiked with internal standard (3,3'-diaminodiphenyl sulfone, 1 µg) before extraction with ethyl acetate (2 x 1 ml). The organic extracts were combined, solvent removed under a gentle stream of nitrogen and the residue dissolved in methanol (100 µl). An aliquot (50 µl) of this solution was then injected onto an octadecyl-bonded silica column (Spherisorb 5 µm ODS2, 25 x 0.46 cm internal diameter [i.d.]) and the compounds eluted with a mobile phase of water/acetonitrile/acetic acid/triethylamine (80:20:1:0.1 v/v) flowing at 1.2 ml/min. The eluate was monitored at 254 nm.
Statistics:
one reported

Results and discussion

Preliminary studies:
TOXICITY :
Toxicity and plasma kinetics of dapsone in the rat and mouse :
Administration of dapsone to male Wistar rats resulted in a time-dependent increase in methemoglobinemia, which reached a maximum of 29.1 +/- 9.3% at 1 h. In contrast, there was no significant increase in methemoglobinemia after administration of dapsone to either the female rat or to the male mouse. The area under the curve (AUC(0–24)) for methemoglobinemia was 348% metHb.h-1 for male rats, 74.0% metHb.h-1 for female rats and 49.7% metHb.h-1 for male mice. Analysis of plasma revealed that in the male rat, peak plasma concentrations of dapsone (29.2 +/- 8.4 µg.ml-1) were reached 2 h after the dose, with a half-life of 7.7 +/- 1.4 h. The area under the curve for dapsone AUC(0–24) was 243.0 +/- 105.6 µg.ml-1.h.
In the female rat, although there was no significant difference in the peak plasma concentrations (32.0 +/- 6.7 µg.ml-1), they were reached 3h after the dose, and declined with a significantly (P < .05) longer halflife of 14.5 +/- 1.0 h. The AUC(0–24) for dapsone was also significantly (P < 0.05) greater at 496.8 +/- 103.3 mg.ml-1.h.
In the male mouse, peak plasm concentrations were 23.4 +/- 2.6 µg.ml-1 after 2 h, declining with a half-life of 7.6 +/- 1.0 h. The AUC(0–24) for dapsone was 233.1 +/- 31.3 mg.ml-1.h.
No dapsone hydroxylamine could be detected in plasma at any time point (limit of detection, 10 ng.ml-1).

Toxicokinetic / pharmacokinetic studies

Details on absorption:
none
Details on distribution in tissues:
Dapsone is distributed in the entire body. Higher levels have been observed in brain, and liver, and in blood. One of the major adverse effects observed is methemoglobinaemia, which is due to the aromatic amino groups present in the molecule.
Transfer into organs
Test no.:
#1
Transfer type:
blood/brain barrier
Observation:
distinct transfer
Details on excretion:
After i.p.injection plasma levels of 4,4-DDS reach a maximum concentration after 2-3 hours (depending on the species tested), and drop sharply to 15% (female rats) and 0-5 % (male rats and male mice).
This is identical to the appearance and disappearance of methemoglobinaemia with a maximum of 30% after 1 hours for male rats and drop sharply to 5% at 24 hours. But there was no significant increase in methemoglobinemia after administration of dapsone to either the female rat or male mice.
The half-life of Dapsone in serum is 7.7 hours (male rats), 14.5 hours (female rats), 7.6 hours (male mouse).
Toxicokinetic parametersopen allclose all
Test no.:
#1
Toxicokinetic parameters:
half-life 1st: 7.7 hours
Test no.:
#2
Toxicokinetic parameters:
half-life 1st: 14.4 hours
Test no.:
#3
Toxicokinetic parameters:
half-life 1st: 7.6 hours

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
Excretion is 46% via bile for male rates compared to 21% for females and 5% via urine for male rates and 3% for females.
The main metabolite was glucuronide of Dapsone in bile.
In Human volunteers, during 24 h postdose, 5.9 +/- 2.6% of the dose was excreted as free (nonconjugated) dapsone, 0.5 +/- 0.3% as free hydroxylamine and 0.6 +/- 0.2% as monoacetyl dapsone. After hydrolysis with ß-glucuronidase, 15.3 +/- 2.4% of the dose was quantified as dapsone and 13.1 +/- 2.6% as dapsone hydroxylamine.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
Dapsone is not bio-accumulating in rats, mice and Humans. Male rats are the most sensitive species tested, while Humans are the least sensitive ones. Dapsone is rapidly excreted with a half-life of 7.7 - 14 hours in all three species. Methemoglobinaemia is the most prominent adverse effects observed. The major metabolite is dapsone-hydroxylamine and Dapsone-hydroxylamine-glucuronide. No bio-accumulation is expected based on the excretion half-life.
Executive summary:

Dapsone is not bio-accumulating in rats, mice and Humans. Male rats are the most sensitive species tested, while Humans are the least sensitive ones. Dapsone is rapidly excreted with a half-life of 7.7 - 14 hours in all three species. Methemoglobinaemia is the most prominent adverse effects observed. The major metabolite is dapsone-hydroxylamine and Dapsone-hydroxylamine-glucuronide. No bio-accumulation is expected based on the excretion half-life.