Histamine H1-receptor, Noradrenaline uptake (α1-and α2-adrenoceptors and serotonin 5HT1 and 5HT2-receptors)[1]

Absorption, Distribution and Excretion
Following oral administration of 25 mg Dothiepin, it is well absorbed through the intestines, reaching a peak plasma concentration of 37.6 ng/mL at 2.18 hours (Tmax). Steady-state concentrations vary from person to person due to the dynamic relationship between drug dose and plasma concentration. Dothiepin is primarily cleared by the kidneys, mainly as metabolites. Renal excretion of Dothiepin and its metabolites accounts for 50%–60% of total clearance, while bile/fecal excretion accounts for approximately 15%–40%. The mean apparent volume of distribution (Vd) after oral administration of 75 mg Dothiepin is approximately 45 L/kg. Dothiepin can cross the blood-brain barrier to exert its antidepressant effect and can also cross the placental barrier, but drug concentrations in breast milk are low. The oral clearance after a single oral dose of 75 mg Dothiepin is approximately 1.36 L/kg/hr. Dothiepin and its metabolites have been detected in breast milk. The average daily total exposure of infants is approximately 4.4% of the mother's Dothiepin dose. Dothiepin is readily absorbed from the gastrointestinal tract. This study evaluated the pharmacokinetics of a single oral dose of 75 mg Dothiepin in nine patients with depression. The concentrations of Dothiepin and its two major metabolites—norticaine and Dothiepin S-oxide—in blood and plasma were determined by gas chromatography/mass spectrometry. The mean (± standard deviation) peak plasma concentration of Dothiepin was 49 ± 27 μg/L, with an onset of action of 3 ± 1.2 hours. The mean (± standard deviation) values for other parameters were as follows: absorption half-life 1.1 ± 1.1 hours; distribution half-life 2.2 ± 0.8 hours; elimination half-life 25 ± 7 hours; apparent volume of distribution 70 ± 62 L/kg; and oral clearance 2.1 ± 1.6 L/kg/hour. The mean (± standard deviation) peak plasma concentration of Dothiepin S-oxide was 125 ± 43 μg/L, with an onset of action of 3.5 ± 1.3 hours and an elimination half-life of 22 ± 12 hours. The mean peak plasma concentration of notetan was 6 ± 3 μg/L, with an onset of action of 4.5 ± 1.1 hours and an elimination half-life of 31 ± 12 hours. No significant differences in pharmacokinetic parameters were found compared to previous studies in 7 healthy volunteers. When data from patients and healthy volunteers were pooled (n = 16), no age-related effects on pharmacokinetic parameters were found. However, significant differences were observed between men and women in the elimination half-life of Dothiepin and notetan, as well as in the apparent volume of distribution of Dothiepin. The 24-hour blood/plasma concentrations of Dothiepin and Dothiepin S-oxide accurately predicted the steady-state concentrations reached after 4 consecutive weeks of bedtime Dothiepin administration of 150 mg. In a three-group randomized crossover dose-ratio study, 27 healthy men received three single oral doses of 50 mg, 100 mg, and 150 mg Dothiepin hydrochloride capsules, respectively. The plasma concentration-time curves of Dothiepin (1) could be described using a one-compartment and a two-compartment model of first-order absorption. As the dose increased from 50 mg to 150 mg, the total intrinsic clearance of Dothiepin decreased from 165.5 L/hr to 121.1 L/hr, but had no significant effect on the terminal half-life (approximately 20 hours). The plasma concentration-time curves of the three major metabolites of Dothiepin—the S-oxide derivative N,N-dimethyl[b,e]thiophene-Δ11(6H)γ-propylamine-5-oxide (2), the demethyl derivative N-methyldibenzo[b,e]thiophene-Δ11(6H)γ-propylamine (3), and the demethyl S-oxide derivative N-methyldibenzo[b,e]thiophene-Δ11(6H)γ-propylamine-5-oxide (4)—can be described using a one-compartment model with apparent first-order reaction kinetics. The AUC∞ values of S-oxide 2 and demethyl S-oxide 4 increase proportionally with dose. The dose-proportional relationship of demethyl metabolite 3 could not be determined from the data in this study. The corresponding half-lives (dose-independent) of the three metabolites are approximately 24, 28, and 40 hours, respectively. /Dothiepin Hydrochloride/
For more complete data on the absorption, distribution, and excretion of Dothiepin (6 metabolites), please visit the HSDB record page.

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Metabolism/Metabolites
Dothiepin is primarily metabolized in the liver to produce the N-demethylated derivative bendearenol (demethylDothiepin or bendearenol) and Dothiepin S-oxide. Bendearen S-oxide is one of the 12 essential metabolites found in urine. The metabolic pathway of Dothiepin is thought to involve N-demethylation, S-oxidation, and glucuronide conjugation.
Dothiepin X-oxide is the major metabolite. Noteden (demethylDothiepin) is an N-demethylated derivative. Both metabolites have antidepressant activity.
In a three-period randomized crossover dose-proportioning study, 27 healthy men received single oral doses of 50 mg, 100 mg, and 150 mg Dothiepin hydrochloride capsules, respectively. A one-compartment model (apparent first-order kinetic model) was used to describe the plasma concentration-time curves of the three major metabolites of Dothiepin—the S-oxide derivative N,N-dimethyl[b,e]thiophene-Δ11(6H)γ-propane-5-oxide (2), the demethyl derivative N-methyldibenzo[b,e]thiophene-Δ11(6H)γ-propane (3), and the demethyl S-oxide derivative N-methyldibenzo[b,e]thiophene-Δ11(6H)γ-propane-5-oxide (4)—. The AUC∞ values of S-oxide 2 and demethyl S-oxide 4 increased proportionally with dose. The data in this study were insufficient to determine the dose-proportional relationship of demethyl metabolite 3. The corresponding half-lives (dose-independent) of the three metabolites were approximately 24, 28, and 40 hours, respectively. /Dothiepin Hydrochloride/
Only small amounts of unbound Dothiepin (unaltered drug) and notetan were excreted in the urine within 72 hours. More than 10% of the dose was excreted as conjugated Dothiepin, while less than 0.8% was excreted as conjugated notitan. Therefore, conjugated Dothiepin is considered an important metabolite of Dothiepin. Both conjugated Dothiepin and notitan can be hydrolyzed by β-glucuronidase, and this hydrolysis can be inhibited by 1,4-glucolactone. Conjugated Dothiepin and benditan were found to be quaternary ammonium-linked glucuronide and tertiary amine N-glucuronide, respectively. Plasma and blood concentrations of two Dothiepin metabolites—benditan and Dothiepin S-oxide—were determined. Dothiepin S-oxide was the major metabolite, reaching a peak concentration of 81 (34–150) μg/L at 5 (4–6) hours. In contrast, benditan reached a peak concentration of only 10 (3–21) μg/L at 5 (4–9) hours. The mean elimination half-life of Dothiepin S-oxide was 19 (13–35) hours, while that of noteden was 33 (22–60) hours.
Biological half-life

After oral administration of 25 mg Dothiepin, the elimination half-life was approximately 20.4 hours.
The β-half-life (elimination) was approximately 20 hours.
The mean absorption half-life was 1.2 hours. The distribution half-life was 2.6 hours.
Seven healthy volunteers received a single oral dose of 75 mg Dothiepin. …The mean estimates are as follows: absorption half-life 1.2 (0.07–3.0) hours, distribution half-life 2.6 (1.1–3.8) hours, elimination half-life 22 (14–40) hours…. The concentrations of Dothiepin S-oxide in plasma and blood, as well as the blood concentrations of two Dothiepin metabolites, were also determined. ...The mean elimination half-life of Dothiepin S-oxide is 19 (13-35) hours, while that of terpenoid is 33 (22-60) hours.

Interactions
In patients with severe overdose of cyclic antidepressants, flumazenil may induce seizures or arrhythmias. /SRP: Flumazenil/

[1]. Dothiepin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in depressive illness. Drugs. 1989 Jul;38(1):123-47.

Dothiepin is a dibenzothiazide compound with dual antidepressant and anticoronavirus effects. Dothiepin (international nonproprietary name: Dothiepin, BAN), formerly known as Dothiepin (USAN), is a tricyclic antidepressant with anxiolytic effects, used in several European and South Asian countries, as well as Australia, South Africa, and New Zealand. Due to its low therapeutic index and significant overdose toxicity, it has not been approved by the U.S. Food and Drug Administration (FDA). Dothiepin increases the availability of neurotransmitters in the synaptic cleft by inhibiting the reuptake of biogenic amines. Dothiepin is only recommended for patients who are intolerant or unresponsive to other antidepressant therapies. Dothiepin is a thiolated derivative of [DB00321], with similar efficacy to [DB00321], and also possesses anticholinergic, antihistamine, and central sedative effects. Its hydrochloride form is a common active ingredient in many pharmaceutical formulations. A tricyclic antidepressant with some sedative effects. Indications Dothiepin is indicated for the treatment of symptoms of depression, particularly in cases requiring anxiolytic activity. Mechanism of Action Dothiepin binds to norepinephrine transporter (NAT) and serotonin transporter (SERT) in an equivalent manner and inhibits their reuptake activity, thereby increasing the levels of free norepinephrine and serotonin (5-HT) in the synaptic cleft. Studies have shown that its major metabolite, terpinene, is more effective than the parent drug in inhibiting norepinephrine uptake. Dothiepin has an affinity for α2-adrenergic receptors and a lower affinity for α1-adrenergic receptors. Dothiepin further enhances its antidepressant effect by promoting norepinephrine release through inhibition of presynaptic α2-adrenergic receptors. It also downregulates central β-adrenergic receptors by reducing the number of receptors and decreases norepinephrine-induced cyclic adenosine monophosphate (cAMP) production. Dothiepin, as an antagonist, binds to 5-HT1A and 5-HT2A receptors in the cerebral cortex and hippocampus. 5-HT1A receptors are autoreceptors that inhibit the release of serotonin (5-HT); 5-HT2A receptors are Gi/Go-coupled receptors, and their activation reduces dopamine release. Antagonism of 5-HT2A receptors may also improve sleep patterns. Furthermore, Dothiepin can bind to muscarinic acetylcholine receptors, causing antimuscarinic side effects such as dry mouth. Dothiepin exerts its sedative effect by antagonizing histamine type 1 (H1) receptors. Its main metabolites, notidine, Dothiepin sulfoxide, and notidine sulfoxide, may also bind to serotonin (5-HT), α2, and H1 receptors, but with lower affinity compared to the parent drug. Dothiepin is a tricyclic antidepressant with a structure similar to amitriptyline. The antidepressant activity of Dothiepin appears to be achieved by promoting noradrenergic neurotransmission through inhibition of norepinephrine uptake, and possibly by enhancing serotonergic neurotransmission. The overall efficacy of Dothiepin is very similar to that of amitriptyline.
Therapeutic Use

Dothiepin is a tricyclic antidepressant with a structure similar to amitriptyline.
Experimental Treatment: This study compared the efficacy of Dothiepin (a tricyclic antidepressant) versus placebo in relieving pain in 60 patients with classic or confirmed active rheumatoid arthritis for 4 weeks. Patients were assigned to a “depressed” or “non-depressed” group. All patients received 600 mg ibuprofen orally three times daily for one week before the start of the study, during the study, and two weeks after the end of the study. Compared with placebo, Dothiepin significantly reduced daytime pain at the end of treatment. Hamilton pain scores were significantly improved in patients in the “depressed” group compared to those taking Dothiepin. In both “depressed” and “non-depressed” patients, the Cassano-Castro-Giovanni Self-Assessment Scale scores showed a trend of improvement (but not significant) in Dothiepin treatment compared to placebo. These results suggest that patients with rheumatoid arthritis may experience worsening pain symptoms due to mood changes. Therefore, treatment with tricyclic antidepressants such as Dothiepin may improve pain indicators in addition to its antidepressant effects.

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Drug Warning
This article reports a case of syndrome of abnormal antidiuretic hormone secretion associated with Dothiepin treatment. The patient was a 39-year-old male with depression, pancytopenia, and portal hypertension, initially taking 75 mg/day, which was later increased to 150 mg/day. The patient developed somnolence, disorientation, and confusion, accompanied by persistent hyponatremia and elevated arginine vasopressin levels. After discontinuation of Dothiepin, the patient received fluid restriction therapy, followed by the addition of demeclocycline. Four days later, serum sodium and osmolality returned to normal, as did arginine vasopressin concentration. This study aimed to determine whether antidepressants are a risk factor for ischemic heart disease and to compare the risks of different subgroups of antidepressants and single antidepressants. This was a case-control study. Participants were drawn from nine general practice clinics within the Trent Focus Collaborative Research Network. A total of 933 patients with ischemic heart disease (men and women) were included and matched with 5516 control participants by age, sex, and clinic. Adjusted odds ratios for ischemic heart disease were calculated using logistic regression. Even after adjusting for factors such as diabetes, hypertension, smoking, body mass index, and the use of selective serotonin reuptake inhibitors, the risk ratio for ischemic heart disease remained significantly elevated in patients who had previously taken tricyclic antidepressants (1.56; 95% confidence interval 1.18 to 2.05). Patients who had previously taken Dothiepin (Dothiepin) had a significantly increased risk ratio for ischemic heart disease after adjusting for confounding factors and the use of other antidepressants (1.67, 1.17 to 2.36). …Increasing the maximum dose of Dothiepin was associated with an increased risk ratio for ischemic heart disease. Similarly, an increase in the number of Dothiepin prescriptions was also significantly positively correlated with the risk ratio for ischemic heart disease (adjusted risk ratios: 1 prescription 1.52, 2–3 prescriptions 1.39, ≥4 prescriptions 1.96, P<0.002). There is sufficient evidence to suggest an association between Dothiepin and subsequent ischemic heart disease, and a dose-response relationship exists.

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Pharmacodynamics
Dothiepin is a tricyclic antidepressant that interacts with multiple receptors and transporters. It is a monoamine reuptake inhibitor with roughly equal potency for norepinephrine and serotonin, increasing the availability of these neurotransmitters at central synapses. Studies have shown that the metabolites of Dothiepin can inhibit the uptake of serotonin by human platelets.

C19H21NS

295.44

295.139

113-53-1

Dothiepin-d3;136765-31-6;Dothiepin-d6 hydrochloride;1276545-35-7

5282426

Off-white to yellow solid powder

1.1±0.1 g/cm3

430.9±44.0 °C at 760 mmHg

55-57ºC

214.4±28.4 °C

0.0±1.0 mmHg at 25°C

1.661

4.34

0

2

3

21

363

0

CN(C)CC/C=C\1/C2=CC=CC=C2CSC3=CC=CC=C31

PHTUQLWOUWZIMZ-BOPFTXTBSA-N

InChI=1S/C19H21NS/c1-20(2)13-7-11-17-16-9-4-3-8-15(16)14-21-19-12-6-5-10-18(17)19/h3-6,8-12H,7,13-14H2,1-2H3/b17-11-

(3Z)-3-(6H-benzo[c][1]benzothiepin-11-ylidene)-N,N-dimethylpropan-1-amine

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)