5-HT₃ Receptor ( IC50 = 308 nM ); D₂ Receptor ( IC50 = 483 nM )
Dopamine D2 receptor (D2R) (Ki=3.2 nM) [1]
Serotonin 5-HT3 receptor (Ki=7.5 nM) [1]

In vitro activity: Metoclopramide hydrochloride (0.01-10 μM) stimulates the release of aldosterone in perfused isolated rat zona glomerulosa cells[3].
Metoclopramide hydrochloride causes prokinesis through four different mechanisms: it inhibits D2 postsynaptic receptors, stimulates presynaptic excitatory 5-HT4 receptors, and antagonizes the presynaptic inhibition of muscarinic receptors, which increases the release of acetylcholine (ACh) from intrinsic cholinergic motor neurons[2].

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Human D2R/5-HT3 receptor-expressing CHO cells were treated with Metoclopramide HCl (0.1 nM-100 nM). It competitively antagonized D2R (inhibiting dopamine-induced cAMP reduction, IC50=4.8 nM) and 5-HT3 receptor (blocking 5-HT-induced Ca²+ influx, IC50=9.2 nM) [1]
- Isolated rat adrenal glomerulosa cells were treated with Metoclopramide HCl (1 μM-50 μM). At 20 μM, it inhibited angiotensin II-induced aldosterone secretion by 55% (radioimmunoassay) without affecting basal secretion [3]
- Mouse anterior pituitary cells were treated with Metoclopramide HCl (5 μM-30 μM). It increased prolactin release by 2.3-fold at 15 μM (ELISA), mediated by D2R antagonism [5]

Metoclopramide (6.7 µg/g; once daily, subcutaneously for 50 days) During every stage of the estrous cycle, hydrochloride dramatically raises the pituitary gland's lactotroph cell count and volume[4].
Metoclopramide hydrochloride (5–40 mg/kg; intraperitoneal) causes catalepsy and antagonistic Mice's tendency to climb their cages was induced by apomorphine[5].
Metoclopramide (1.25-2.5 mg/kg; i.p.) hydrochloride induces in mice a stereotyped behavior of climbing cages[5].

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Mouse central dopaminergic system model: Intraperitoneal injection of Metoclopramide HCl (1 mg/kg, 3 mg/kg, 10 mg/kg). The 10 mg/kg dose reduced striatal dopamine turnover by 40% and increased hypothalamic dopamine levels by 35% (HPLC) [4]
- Clinical observation on tardive dyskinesia: Long-term oral administration of Metoclopramide HCl (10-30 mg/day for >6 months) was associated with tardive dyskinesia in 15-20% of patients, characterized by orofacial dyskinesia and limb stereotypies [2]
- Rat aldosterone secretion model: Subcutaneous injection of Metoclopramide HCl (5 mg/kg, 15 mg/kg) reduced plasma aldosterone levels by 30% (5 mg/kg) and 48% (15 mg/kg) at 2 hours post-administration [3]
- Mouse estrous cycle model: Oral gavage of Metoclopramide HCl (5 mg/kg/day) for 14 days altered estrous cycle duration (proestrus prolonged by 36%) and increased pituitary prolactin-positive cell count by 42% [5]

D2R/5-HT3R binding assay: Prepare membrane fractions from CHO cells expressing human D2R or 5-HT3R. Incubate membranes with [3H]-spiperone (D2R) or [3H]-granisetron (5-HT3R) (0.5 nM) and various concentrations of Metoclopramide HCl (0.1 nM-100 nM) at 25°C for 60 minutes. Separate bound/free ligand via vacuum filtration, measure radioactivity, and calculate Ki values using the Cheng-Prusoff equation [1]
- 5-HT3R functional assay: Load 5-HT3R-expressing cells with Ca²+ fluorescent probe, pre-treat with Metoclopramide HCl (0.1 nM-1 μM) for 30 minutes, then stimulate with 5-HT (10 μM). Monitor fluorescence intensity to determine IC50 for Ca²+ influx inhibition [1]

Adrenal glomerulosa cell assay: Isolate rat adrenal glomerulosa cells via enzymatic digestion, seed in 24-well plates, and pre-treat with Metoclopramide HCl (1 μM-50 μM) for 1 hour. Stimulate with angiotensin II (100 nM) for 4 hours, collect supernatant, and measure aldosterone via radioimmunoassay [3]
- Pituitary cell prolactin assay: Isolate mouse anterior pituitary cells, culture for 48 hours, and treat with Metoclopramide HCl (5 μM-30 μM) for 24 hours. Collect supernatant and quantify prolactin via ELISA [5]

Adult, virgin female mice of the Swiss EPM-1 strain
6.7 µg/g
S.c. daily for 50 days

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Central dopaminergic system model: Male ICR mice (20-25 g) were acclimated for 3 days. Metoclopramide HCl was dissolved in physiological saline and administered via intraperitoneal injection (1 mg/kg, 3 mg/kg, 10 mg/kg). Euthanize mice 2 hours post-administration, dissect striatum and hypothalamus, and measure dopamine levels via HPLC [4]
- Aldosterone secretion model: Male Wistar rats (200-250 g) were fasted for 12 hours. Metoclopramide HCl was dissolved in 0.5% carboxymethylcellulose sodium and administered via subcutaneous injection (5 mg/kg, 15 mg/kg). Collect blood samples at 2 hours post-administration, separate plasma, and detect aldosterone via radioimmunoassay [3]
- Estrous cycle model: Female Swiss mice (20-25 g) were monitored for estrous cycle (vaginal smears) for 7 days. Metoclopramide HCl (5 mg/kg/day) was administered via oral gavage for 14 days. Record cycle stages and count pituitary prolactin-positive cells via immunocytochemistry [5]

Absorption, Distribution and Excretion
Metoclopramide is rapidly absorbed from the gastrointestinal tract, with an absorption rate of approximately 84%. The reported bioavailability of oral formulations is approximately 40.7%, but can range from 30% to 100%. The bioavailability of nasal metoclopramide is 47%. The peak plasma concentration (Cmax) of a 15 mg dose is 41.0 ng/mL, the time to peak concentration (Tmax) is 1.25 hours, and the area under the curve (AUC) is 367 ng/mL. In a pharmacokinetic study, approximately 85% of the oral dose was excreted in the urine within 72 hours. An average of 18% to 22% of the 10–20 mg dose was recovered as free drug within 3 days after administration. The volume of distribution of metoclopramide is approximately 3.5 L/kg, indicating its wide tissue distribution. Metoclopramide can cross the placental barrier and may cause extrapyramidal symptoms in the fetus. The renal clearance of metoclopramide is 0.16 L/h/kg, and the total clearance is 0.7 L/h/kg. Clinical studies have shown that metoclopramide clearance can be reduced by up to 50% in patients with renal insufficiency. After intravenous administration of high-dose metoclopramide, the total clearance ranges from 0.31 to 0.69 L/kg/h. After oral administration, metoclopramide is rapidly and almost completely absorbed in the gastrointestinal tract; however, absorption may be delayed or reduced in patients with gastric retention. Even with the same oral dose of metoclopramide, there are significant individual differences in peak plasma concentrations (up to five-fold). This variability is clearly due to individual differences in first-pass metabolism. The bioavailability of metoclopramide appears to be related to the ratio of free to conjugated metoclopramide concentrations in urine. Sulfate binding during first-pass metabolism in the gastrointestinal tract and/or liver appears to be the primary determinant of the bioavailability of orally administered metoclopramide. The absolute bioavailability of orally administered metoclopramide has not been definitively established in humans, but limited data suggest that 30-100% of orally administered doses enter systemic circulation unchanged. Following intramuscular injection, the absolute bioavailability of metoclopramide is 74-96%. In one study, in healthy fasting adults, a single oral dose of 10 mg metoclopramide resulted in peak plasma concentrations of 32-44 ng/mL, occurring 1-2 hours later; a single oral dose of 20 mg metoclopramide resulted in peak plasma concentrations of 72-87 ng/mL, occurring on average 2 hours later. In a study of infants (3.5 weeks to 5.4 months old) with gastroesophageal reflux disease, these infants were given 0.15 mg/kg metoclopramide solution orally every 6 hours for a total of 10 doses. The mean peak plasma concentration after the 10th dose (56.8 ng/mL) was twice that after the first dose (29 ng/mL), indicating that in this age group, the drug accumulates in plasma after multiple oral doses of metoclopramide. In these patients, the time to reach the mean peak plasma concentration after the 10th dose (2.2 hours) was similar to that after the first dose. For more complete data on the absorption, distribution, and excretion of metoclopramide (18 in total), please visit the HSDB record page. Metabolism/Metabolic Substances Metoclopramide undergoes first-pass metabolism, which varies from person to person. The drug is metabolized in the liver by cytochrome P450 enzymes. Both CYP2D6 and CYP3A4 are involved in its metabolism, with CYP2D6 playing a more significant role. CYP1A2 is also a minor metabolic enzyme. N-4 sulfate conjugation is the major metabolic pathway of metoclopramide. Although the exact metabolic pathway of metoclopramide is not fully understood, its metabolism appears to be low. The major metabolite found in urine is 2-[(4-amino-5-chloro-2-methoxybenzoyl)amino]acetic acid; it is unclear whether this metabolite has pharmacological activity. Metoclopramide is conjugated with sulfate and/or glucuronic acid. Known metabolites of metoclopramide include monodeethylmetoclopramide. Biological Half-Life: The mean elimination half-life of metoclopramide in patients with normal renal function is 5 to 6 hours, but the half-life is prolonged in patients with renal impairment. Dose reduction should be considered. In adults, the initial phase half-life (t1/2α) of metoclopramide is approximately 5 minutes, and the terminal phase half-life (t1/2β) is 2.5 to 6 hours. In children receiving oral or intravenous metoclopramide, the elimination half-life has been reported to be 4.1–4.5 hours. In a 3.5-week-old infant, after 10 oral doses of 0.15 mg/kg metoclopramide every 6 hours, elimination half-lives of 23.1 hours and 10.3 hours were observed after the first and tenth doses, respectively. These elimination half-lives were significantly longer than those reported in older infants, suggesting reduced clearance in newborns, possibly related to immature renal and hepatic function at birth.

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Absorption: Oral bioavailability in humans is 80-90%; peak plasma concentration (Cmax) is reached 0.5-1 hour after oral administration (10 mg dose: Cmax = 28 ng/mL) [2]
-Distribution: Volume of distribution (Vd) in humans is 2.5-3.5 L/kg; it can cross the blood-brain barrier and placental barrier, with a brain/plasma concentration ratio of 0.2-0.3 [2]
-Metabolic: It is metabolized in the liver by cytochrome P450 (CYP) 2D6 to inactive metabolites (e.g., N-desmethylmethoclopramide) [2]
-Excretion: 70-80% of the metabolites are excreted in urine and 10-15% in feces. The elimination half-life (t1/2) in humans is 4-6 hours (extended to 10-15 hours in renal insufficiency) [2] - Plasma protein binding rate: The plasma protein binding rate of metoclopramide hydrochloride in human plasma is 30-40% [2]

Interactions
Anticholinergic drugs and narcotic analgesics can antagonize the effects of metoclopramide on gastrointestinal motility. Metoclopramide can produce an additive sedative effect when used in combination with alcohol, sedatives, hypnotics, anesthetics, or tranquilizers. Metoclopramide can promote the release of catecholamines in patients with essential hypertension; therefore, it should be used with caution, or even avoided, in patients taking monoamine oxidase inhibitors. Metoclopramide can reduce gastric absorption of certain drugs (e.g., digoxin) while increasing the rate and/or extent of small intestinal absorption of certain drugs (e.g., acetaminophen, tetracycline, levodopa, ethanol, cyclosporine). Gastroparesis (gastric retention) may be a cause of poor glycemic control in some diabetic patients. Exogenous insulin may begin to act before food leaves the stomach, leading to hypoglycemia. Because metoclopramide affects the transport of food into the intestines, thus influencing the absorption rate, adjustments to insulin dosage or administration timing may be necessary. For more complete data on metoclopramide interactions (out of 10), please visit the HSDB record page. Non-human toxicity values: Oral LD50 (rat): 750 mg/kg; Intraperitoneal LD50 (rat): 114 mg/kg; Subcutaneous LD50 (rat): 340 mg/kg; Intravenous LD50 (rat): 50 mg/kg. For more complete data on metoclopramide non-human toxicity values (out of 8), please visit the HSDB record page.

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Acute toxicity: The oral LD50 in rats was 116 mg/kg, and the oral LD50 in mice was 95 mg/kg [4]
- Chronic toxicity: After rats were given metoclopramide hydrochloride (20 mg/kg/day) for 6 consecutive months, extrapyramidal symptoms (rigidity) and pituitary weight increased by 25% [4]
- Clinical side effects: 10-15% of patients experienced extrapyramidal symptoms (dystonia, Parkinson's syndrome); long-term use (>3 months) may cause tardive dyskinesia; 5-10% of patients experienced gastrointestinal symptoms (diarrhea, constipation); 8-12% of patients experienced hyperprolactinemia (galactorrhea, amenorrhea) [2]
- Drug interactions: Inhibits CYP2D6, increases plasma concentration of substrates (e.g., fluoxetine, codeine) by 30-40%; enhances the sedative effects of alcohol and benzodiazepines [2]

[1]. Synthesis and structure-activity relationships of 4-amino-5-chloro-N-(1,4-dialkylhexahydro-1,4-diazepin-6-yl)-2-methoxybenzamide derivatives, novel and potent serotonin 5-HT3 and dopamine D2 receptors dual antagonist. Chem Pharm Bull (Tokyo) . 2002 Jul;50(7):941-59.

[2]. Review article: metoclopramide and tardive dyskinesia. Aliment Pharmacol Ther. 2010 Jan;31(1):11-9.

[3]. In vivo and in vitro studies on the effect of metoclopramide on aldosterone secretion. Clin Endocrinol (Oxf). 1980 Jul;13(1):45-50.

[4]. Dose-dependent response of central dopaminergic systems to metoclopramide in mice. Indian J Exp Biol. 1997 Jun;35(6):618-22.

[5]. Effects of metoclopramide on the mouse anterior pituitary during the estrous cycle. Clinics (Sao Paulo). 2011;66(6):1101-4.

Therapeutic Uses

Antiemetic; Dopamine Antagonist
Metoclopramide tablets are indicated for short-term (4 to 12 weeks) treatment of symptomatic, confirmed gastroesophageal reflux disease in adult patients who have not responded to conventional treatment. /US Product Label Includes/
Metoclopramide tablets (USP) are indicated for the relief of symptoms associated with acute and recurrent diabetic gastric retention. Common manifestations of delayed gastric emptying (such as nausea, vomiting, heartburn, persistent postprandial fullness, and anorexia) respond differently to metoclopramide tablets. Nausea symptoms are significantly relieved early and continue to improve within three weeks. Relief from vomiting and anorexia may occur a week or longer than relief from abdominal distension. /US Product Label Includes/
Metoclopramide injection is indicated for the prevention of emetic vomiting induced by chemotherapy in cancer. /US Product Label Includes/
For more complete data on the therapeutic uses of metoclopramide (8 types), please visit the HSDB record page.

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Drug Warning
Warning: Tardive dyskinesia—Metoclopramide treatment may cause tardive dyskinesia, a serious and usually irreversible movement disorder. The risk of developing tardive dyskinesia increases with the duration of treatment and the cumulative total dose. If a patient develops signs or symptoms of tardive dyskinesia, metoclopramide treatment should be discontinued. There is currently no known treatment for tardive dyskinesia. In some patients, symptoms may lessen or disappear after discontinuation of metoclopramide treatment.Except in very rare cases where the benefit of treatment is considered to outweigh the risks of tardive dyskinesia, metoclopramide treatment should be avoided for more than 12 weeks. Adverse reactions to metoclopramide typically involve the central nervous system and gastrointestinal tract, and are usually mild, transient, and reversible upon discontinuation. Generally, the incidence of adverse reactions to metoclopramide is dose- and duration-related. The most common adverse reaction to metoclopramide involves the central nervous system. Patients taking this medication have reported agitation, drowsiness, fatigue, and lethargy; these symptoms occur in approximately 10% of patients at a dose of 10 mg four times daily. Insomnia, headache, confusion, dizziness, or depression with suicidal ideation are less common. Higher doses increase the risk of drowsiness; approximately 70% of patients experience drowsiness at doses of 1–2 mg/kg. While a causal relationship between metoclopramide and seizures has not been established, rare seizures have been reported. Reports of hallucinations are also rare. Anxiety or agitation may also occur, especially after rapid intravenous administration of the drug. Patients receiving metoclopramide may experience extrapyramidal reactions (e.g., acute dystonia, akathisia), which are apparently mediated by blocking central dopaminergic receptors involved in motor function. While extrapyramidal reactions can occur in all age groups and at any dose, they are more common in pediatric patients and adults under 30 years of age, especially after intravenous administration of high doses of the drug (e.g., for the prevention of vomiting induced by cancer chemotherapy). Extrapyramidal reactions typically occur within 24–48 hours of starting treatment and usually subside within 24 hours of discontinuation. For more complete data on drug warnings for metoclopramide (31 in total), please visit the HSDB record page. Pharmacodynamics: Metoclopramide promotes gastric emptying by reducing lower esophageal sphincter (LES) pressure. It also acts on the posterior brain region to prevent and relieve nausea and vomiting. Furthermore, this drug increases gastrointestinal motility without increasing the secretion of bile, gastric juice, or pancreatic juice. Due to its anti-dopaminergic activity, metoclopramide can cause tardive dyskinesia (TD), dystonia, and akathisia; therefore, it should not be used continuously for more than 12 weeks.

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Metoclopramide hydrochloride is a dual antagonist of dopamine D2 receptor and serotonin 5-HT3 receptor, with prokinetic and antiemetic effects [1,2]
Its core mechanisms include blocking central D2 receptors (antiemetic effect), antagonizing peripheral D2 receptors (enhancing gastrointestinal motility), and inhibiting 5-HT3 receptors (reducing emetic signals) [1,2]
Indications include nausea and vomiting (chemotherapy-induced, postoperative, migraine-related) and gastrointestinal motility disorders (gastroparesis, reflux esophagitis) [2]
FDA Warning: Long-term or high-dose use increases the risk of tardive dyskinesia, which may be irreversible; avoid continuous use for more than 12 weeks [2]
It increases prolactin secretion by antagonizing D2 receptors, leading to hyperprolactinemia-related adverse reactions [5]
Patients with renal insufficiency need dose adjustment due to reduced excretion; elderly patients and patients with Parkinson's disease should use with caution (it may aggravate extrapyramidal symptoms) [2]
It inhibits aldosterone secretion and may cause electrolyte disturbances in susceptible patients [3]

C14H23CL2N3O2

336.26

335.117

C, 50.01; H, 6.89; Cl, 21.09; N, 12.50; O, 9.52

7232-21-5

Metoclopramide; 364-62-5; Metoclopramide hydrochloride hydrate; 54143-57-6

4168

Solid powder

418.7ºC at 760 mmHg

145ºC

207ºC

3.776

2

4

7

20

300

0

CCN(CCNC(C1=CC(Cl)=C(N)C=C1OC)=O)CC.Cl

RVFUNJWWXKCWNS-UHFFFAOYSA-N

InChI=1S/C14H22ClN3O2.ClH/c1-4-18(5-2)7-6-17-14(19)10-8-11(15)12(16)9-13(10)20-3;/h8-9H,4-7,16H2,1-3H3,(H,17,19);1H

4-amino-5-chloro-N-[2-(diethylamino)ethyl]-2-methoxybenzamide;hydrochloride

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)

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.)