In B\PC3 and Capan-2 cells, carbidetopa ((S)-(-)-carbidopa) monohydrate demonstrates activity akin to those of other AhR ligands, specifically inducing CYP1A1 and CYP1A2, which can be controlled by AhR Antagonists (e.g., CH223191) block [1]. Carbidopa is an inhibitor of aromatic-L-amino acid decarboxylase that exhibits specific cytotoxicity against small cell lung cancer cells and human lung carcinooids. Carbidopa's fatal dose is 29 μM (IC50)[3].

In vivo research revealed that a dose of 1 mg/mouse of carbidopa greatly suppressed tumor growth in athymic nude mice carrying BχPC3 cells as xenografts [1]. Carbidopa monohydrate also stimulates nuclear absorption of AhR.

Absorption, Distribution and Excretion
When [levodopa]/carbidopa is administered orally, 40-70% of the administered dose is absorbed. Once absorbed, carbidopa shows bioavailability of 58%. A maximum concentration of 0.085 mcg/ml was achieved after 143 min with an AUC of 19.28 mcg.min/ml.
In animal studies, 66% of the administered dose of carbidopa was eliminated via the urine while 11% was found in feces. These studies were performed in humans and it was observed a urine excretion covering 50% of the administered dose.
The volume of distribution reported for the combination therapy of carbidopa/[levodopa] is of 3.6 L/kg. However, carbidopa is widely distributed in the tissues, except in the brain. After one hour, carbidopa is found mainly in the kidney, lungs, small intestine and liver.
The reported clearance rate for the combination therapy of [levodopa]/carbidopa is 51.7 L/h.

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Metabolism / Metabolites
The loss of the hydrazine functional group (probably as molecular nitrogen) represents the major metabolic pathway for carbidopa. There are several metabolites of carbidopa metabolism including 3-(3,4-dihydroxyphenyl)-2-methylpropionic acid, 3-(4-hydroxy-3-methoxyphenyl)-2-methylpropionic acid, 3-(3-hydroxyphenyl)-2-methylpropionic acid, 3-(4-hydroxy-3-methoxyphenyl)-2-methyllactic acid, 3-(3-hydroxyphenyl)-2-methyllactic acid, and 3,4-dihydroxyphenylacetone (1,2).

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Biological Half-Life
The reported half-life of carbidopa is of approximately 107 minutes.

Protein Binding
It is widely accepted that the protein binding of carbidopa is 76%. However, more studies are required or the presentation of the source of this information.

[1]. Safe S. Carbidopa: a selective Ah receptor modulator (SAhRM). Biochem J. 2017;474(22):3763-3765. Published 2017 Nov 6.

[2]. Fermaglich J. Treatment of Parkinson's disease with carbidopa, a peripheral decarboxylase inhibitor, and levodopa. Med Ann Dist Columbia. 1974;43(12):587-591.

[3]. The aromatic-L-amino acid decarboxylase inhibitor carbidopa is selectively cytotoxic to human pulmonary carcinoid and small cell lung carcinoma cells. Clin Cancer Res. 2000;6(11):4365-4372.

Carbidopa is the hydrate of 3-(3,4-dihydroxyphenyl)propanoic acid in which the hydrogens alpha- to the carboxyl group are substituted by hydrazinyl and methyl groups (S-configuration). Carbidopa is a dopa decarboxylase inhibitor, so prevents conversion of levodopa to dopamine. It has no antiparkinson activity by itself, but is used in the management of Parkinson's disease to reduce peripheral adverse effects of levodopa. It has a role as an EC 4.1.1.28 (aromatic-L-amino-acid decarboxylase) inhibitor, an antiparkinson drug, a dopaminergic agent and an antidyskinesia agent. It is a member of hydrazines, a hydrate, a monocarboxylic acid and a member of catechols. It contains a carbidopa (anhydrous).
Carbidopa presents a chemical denomination of N-amino-alpha-methyl-3-hydroxy-L-tyrosine monohydrate. It potently inhibits aromatic amino acid decarboxylase (DDC) and due to its chemical properties, it does not cross the blood-brain barrier. Due to its activity, carbidopa is always administered concomitantly with [levodopa]. An individual formulation containing solely carbidopa was generated to treat nausea in patients where the combination therapy [levodopa]/carbidopa is not efficient reducing nausea. The first approved product by the FDA containing only carbidopa was developed by Amerigens Pharmaceuticals Ltd and approved on 2014. On the other hand, the combination treatment of carbidopa/levodopa was originally developed by Watson Labs but the historical information by the FDA brings back to the approval of this combination therapy developed by Mayne Pharma in 1992.
Carbidopa is an Aromatic Amino Acid Decarboxylation Inhibitor. The mechanism of action of carbidopa is as a DOPA Decarboxylase Inhibitor.
Carbidopa is a hydrazine derivative of dopa. Carbidopa is a peripheral dopa decarboxylase inhibitor that is used as an adjunct to levodopa administration to prevent peripheral biosynthesis of levodopa to dopamine, thereby reducing peripheral side effects. Carbidopa does not penetrate the blood brain barrier so that levodopa, after it reaches the brain, can be metabolized to dopamine by dopa decarboxylase where it exerts its effect on dopamine receptors.
An inhibitor of DOPA DECARBOXYLASE that prevents conversion of LEVODOPA to dopamine. It is used in PARKINSON DISEASE to reduce peripheral adverse effects of LEVODOPA. It has no anti-parkinson activity by itself.

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Drug Indication
Carbidopa is indicated with [levodopa] for the treatment of symptoms of idiopathic Parkinson disease, postencephalitic parkinsonism and symptomatic parkinsonism followed by carbon monoxide or manganese intoxication. The combination therapy is administered for the reduction of [levodopa]-driven nausea and vomiting. The product of carbidopa should be used in patients where the combination therapy of carbidopa/[levodopa] provide less than the adequate daily dosage. As well carbidopa can be used in patients where the dosages of carbidopa and [levodopa] require individual titration.
FDA Label

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Mechanism of Action
Carbidopa is an inhibitor of the DDC which in order, inhibits the peripheral metabolism of levodopa. DDC is very important in the biosynthesis of L-tryptophan to serotonin and the modification of L-DOPA to dopamine. DDC can be found in the body periphery and in the blood-brain barrier. The action of carbidopa is focused on peripheral DDC as this drug cannot cross the blood-brain barrier. Hence, it will prevent the metabolism of [levodopa] in the periphery but it will not have any activity on the generation of dopamine in the brain.

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Pharmacodynamics
When mixed with [levodopa], carbidopa inhibits the peripheral conversion of [levodopa] to dopamine and the decarboxylation of [oxitriptan] to serotonin by aromatic L-amino acid decarboxylase. This results in an increased amount of [levodopa] and [oxitriptan] available for transport to the central nervous system. Carbidopa also inhibits the metabolism of [levodopa] in the GI tract, thus, increasing the bioavailability of [levodopa]. The presence of additional units of circulating [levodopa] can increase the effectiveness of the still functional dopaminergic neurons and it has been shown to alleviate symptoms for a time. The action of carbidopa is very important as [levodopa] is able to cross the blood-brain barrier while dopamine cannot. Hence the administration of carbidopa is essential to prevent the transformation of external [levodopa] to dopamine before reaching the main action site in the brain. The coadministration of carbidopa with [levodopa] has been shown to increase the half-life of [levodopa] more than 1.5 times while increasing the plasma level and decreasing clearance. The combination therapy has also shown an increase of the recovery of [levodopa] in urine instead of dopamine which proves a reduced metabolism. This effect has been highly observed by a significant reduction in [levodopa] requirements and a significant reduction in the presence of side effects such as nausea. It has been observed that the effect of carbidopa is not dose-dependent.

C10H16N2O5

244.2444

244.105

38821-49-7

Carbidopa;28860-95-9;Carbidopa-d3 monohydrate;1276197-58-0

38101

White to off-white solid powder

1.42 g/cm3

528.7ºC at 760 mmHg

203-208 °C

273.5ºC

0.973

6

7

4

17

261

1

C[C@](CC1=CC(=C(C=C1)O)O)(C(=O)O)NN.O

QTAOMKOIBXZKND-PPHPATTJSA-N

InChI=1S/C10H14N2O4.H2O/c1-10(12-11,9(15)16)5-6-2-3-7(13)8(14)4-6;/h2-4,12-14H,5,11H2,1H3,(H,15,16);1H2/t10-;/m0./s1

(2S)-3-(3,4-dihydroxyphenyl)-2-hydrazinyl-2-methylpropanoic acid;hydrate

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.)