Absorption, Distribution and Excretion
Metabolism in humans and animals: Promethazine is readily absorbed and metabolized in vivo. In rats, 72 hours after a single oral dose of promethazine, 66% of the dose was excreted in the urine and 23% in the feces. The study also showed that 77% of the dose was absorbed into the bloodstream via the gastrointestinal tract. Promethazine or its metabolites were detected in the lungs, spleen, heart, kidneys, and brain of rats 8 days after administration. In a rat metabolism study, promethazine was administered via a single gavage of 1.0 or 100 mg/kg labeled promethazine, or via daily gavage of 1.0 mg/kg unlabeled promethazine for 14 consecutive days, followed by a single gavage of 1.0 mg/kg labeled promethazine. All treatments used corn oil as a solvent. There were no animal deaths during the study period, and the overall weight balance ranged from 97.0% to 105.7% across all treatment groups. Promethazine is rapidly absorbed from the gastrointestinal tract, and absorption was similar across study groups with no significant sex differences observed. The absorption rate was 73% based on recovery in urine/cage flushing fluid and tissues. Within 48 hours of administration, 82% to 95% of the administered dose was recovered in excrement, primarily in urine. No specific target organs were identified. Labeled promethazine was recovered only in the feces of male and female rats in the single high-dose group and female rats in the low-dose group. It is currently unclear whether this recovered promethazine is unabsorbed or has undergone enterohepatic circulation. In preliminary experiments, CO2 was detected at less than 0.1% of the administered dose. A total of 13 metabolites were recovered, of which 3 have been identified. Parent hydroxyl derivatives have been reported to be detected during the degradation of chlorotriazine in animals. In rats administered attenuated with 14C-labeled atrazine, simazine, and promethazine, only trace amounts (a few percent) of radioactive material were observed in urine and feces. When rats were administered ring-labeled promethazine via gastric tube at doses of 41–56 mg/kg, excretion of radioactive material was most rapid in the first 24 hours, decreasing to trace levels after 72 hours. At this point, 65.8% and 23% of the radioactive material were recovered from urine and feces, respectively. Four days later, tissue concentrations of the relevant compound, calculated as promethazine, ranged from 19.8 to 39.3 ppm, with the lowest concentrations in the liver and lungs. Concentrations in all tissues decreased slowly, with corresponding ranges of 13.0–30.3 ppm after eight days. The concentration of this substance was often higher in the skin of animal carcasses after evisceration. It is primarily absorbed through plant roots. …After root absorption, the substance is transported upwards in the xylem and accumulates in the apical meristem and leaves of plants.

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Metabolism / Metabolites
In animals, the major urinary metabolites of atrazine, simazine, and promethazine are the corresponding N-dealkyltriazine compounds, namely 2-chloro-4-amino-6-(ethylamino)-triazine and 2-chloro-4-amino-6-(isopropylamino)-triazine. A third metabolite, 2-chloro-4,6-diamino-triazine, was also detected in the urine of rats administered these three parent compounds. This compound was the major metabolite in rat urine. After administration of promethazine to lactating goats, 16 metabolites were isolated by urinary ion-exchange chromatography, but were not identified. The dealkylation and oxidation of the isopropyl side chain moiety produced carbon dioxide. In a goat metabolism study, a lactating goat was orally supplemented with 9.9 ppm of [14C]promethazine (approximately 20 times the estimated 0.5 ppm in the diet) for seven consecutive days. The results showed that the total radioactive residues (TRR) in milk ranged from 0.080 to 0.238 ppm, in liver 1.123 ppm, in kidney 1.041 ppm, in muscle 0.209 ppm, and in fat 0.160 ppm. Maternal promethazine was not detected in goat milk or tissues. The chlorinated metabolite G-28273 (DACT) was the major residue in milk (63.4% of total radioactive residues, 0.141 ppm), fat (50.4% of total radioactive residues, 0.080 ppm), muscle (26.1% of total radioactive residues, 0.054 ppm), and liver (2.7% of total radioactive residues, 0.031 ppm). Metabolite G-30033 was detected in milk (9.4% of total radioactive residue, 0.021 ppm), but not in tissues. Residual radioactivity in goat milk and tissues was identified as consisting of up to six unknown metabolites. While each unknown metabolite accounted for less than 7% of the total radioactive residue in milk, several were present in higher concentrations in goat tissues. None of these unknown residues were cochromatographically separated from 17 reference standards, including standards for known chlorinated and hydroxyl metabolites of triazine herbicides. Another goat metabolism study used a radiolabeled promethazine hydroxyl metabolite as the test substance. For three consecutive days, lactating goats were orally fed a diet supplemented with 10.9 ppm of [U-14C]2-hydroxypromethazine. The results showed that the total residual amount (TRR) in milk was 0.025–0.029 ppm, in muscle 0.006 ppm, in fat (kidneys and omentum) 0.001 ppm, in kidney 0.110 ppm, and in liver 0.036 ppm. Due to the low radioactivity (<0.010 ppm) in muscle and fat tissue, residue analysis was not performed. 2-hydroxypromethazine was the major residue in all matrices, accounting for 63.5% (0.069 ppm) of the total residual amount (TRR) in the kidneys, 77.2% (0.028 ppm) in the liver, and 65.0–69.4% (0.017–0.020 ppm) in milk. The only other metabolite identified was desisopropylhydroxypromethazine, detected in small amounts in all matrices: 2.9% (0.003 ppm) of the TRR in the kidney, 3.6% (0.001 ppm) of the TRR in the liver, and 8.2–8.5% (0.002 ppm) of the TRR in breast milk. For more complete metabolite/metabolite data on promethazine (16 metabolites in total), please visit the HSDB record page.

Toxicity Summary
Promethazine is a systemic herbicide, typically applied to the soil and absorbed through the leaves and roots, exerting its effect by inhibiting photosynthesis in the target plant. It is a selective herbicide used to control most annual grasses and broadleaf weeds before or after weed emergence. Promethazine is formulated as a flowable concentrate and is registered for use in greenhouse potted ornamental plants, and can only be applied via flood or drip irrigation. …Promethazine has low acute toxicity via oral (Class IV), dermal (Class IV), and inhalation (Class III) routes. It does not irritate the eyes or skin and does not cause skin sensitization. In a subchronic developmental study, fetal bone formation or ossification incomplete or absent ossification was observed in pregnant rats after exposure to promethazine. These developmental effects are considered to occur after a single exposure and should therefore be considered in acute exposure scenarios assessing dietary risk. These adverse reactions form the basis for determining developmental endpoints of acute dietary exposure to promethazine in women aged 13 to 49 years. The highest dose or exposure level at which these adverse reactions were not observed (“NOAEL” or “no adverse reaction observed”) in female rats was 10 mg/kg/day. Subchronic and chronic exposure to promethazine has resulted in neuroendocrine effects in multiple species, leading to reproductive and developmental consequences considered relevant to humans. These neuroendocrine effects are biomarkers of neuroendocrine toxicity mechanisms shared by various structurally related chlorotriazine compounds, including atrazine, simazine, and their three chlorodegradation products—G-28279 (desopropyl atrazine or DIA), G-30033 (desethyl atrazine or DEA), and G-28273 (diaminochlorotriazine or DACT)). G-28273 and DACT are products of promethazine degradation. These six compounds disrupt a part of the central nervous system—the hypothalamic-pituitary-gonadal axis (HPG axis)—leading to cascaded changes in hormone levels and developmental delays. For promethazine, a study on the inhibition of luteinizing hormone (LH) peaks in female rats exposed to atrazine found that long-term dietary exposure led to altered estrous cycles and inhibition of LH peaks, thus establishing the neuroendocrine endpoint of promethazine. The corresponding no-observed-adverse-effect level (NOAEL) was 1.8 mg/kg/day. …The two chlorinated degradation products of promethazine, DEA and DACT, are considered to have the same toxicity as the parent compound due to their shared neuroendocrine toxicity mechanism. Another degradation product, hydroxypromethazine, has been identified, and based on toxicological data from hydroxyatrazine, a metabolite similar to atrazine, its toxicological characteristics are expected to differ from those of promethazine. …

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Non-Human Toxicity Values
Oral LD50 in rats > 7000 mg/kg
Dermal LD50 in rats > 3100 mg/kg
Oral LD50 in mice > 5000 mg/kg
Oral LD50 in rats > 5000 mg/kg /Milogard 80W/
For more complete data on non-human toxicity values of promethazine (18 in total), please visit the HSDB record page.

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Toxicity Data
LC50 (rat) >1220 mg/m3

According to the U.S. Environmental Protection Agency (EPA), promethazine may cause developmental toxicity and female reproductive toxicity. Promethazine is a diamino-1,3,5-triazine, chemically named N,N'-di(propyl-2-yl)-1,3,5-triazine-2,4-diamine, with a chlorine substitution at the 6-position. It is a herbicide, exogenous substance, and environmental pollutant. It is both a chloro-1,3,5-triazine and a diamino-1,3,5-triazine. Promethazine is a herbicide used to control broadleaf weeds and annual grasses in sweet sorghum fields. It is applied at or immediately after sowing, but must be done before weeds or sorghum emerge. It can also be used as a post-emergence selective herbicide for carrots, celery, and fennel. Promethazine is classified as a slightly toxic compound by the EPA's Toxicity Category III and is listed as a general-purpose pesticide.
Relatively non-toxic triazine herbicides; minor descriptors (75-82); online and medical index search for triazines (75-82)

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Mechanism of Action
…Promethazine is grouped with several structurally related chlorotriazine compounds (e.g., atrazine, simazine, and three chlorotriazine degradation products shared by atrazine, simazine, and promethazine) because they all have toxic mechanisms that disrupt the hypothalamic-pituitary-gonadal axis (HPG axis). Due to their shared toxic mechanisms, exposure to promethazine, like exposure to atrazine, leads to reproductive and developmental effects and consequences considered relevant to humans. These effects form the basis for the selection of regulatory endpoints for both compounds. This mechanism involves central nervous system (CNS) toxicity, specifically alterations in neurotransmitters and neuropeptides at the hypothalamic level, leading to a cascade of changes in hormone levels, such as inhibition of the preovulatory surge of luteinizing hormone, resulting in prolonged estrus in adult female rats (already demonstrated in atrazine and promethazine), and developmental delays, specifically delayed vaginal opening and prepuce separation in developing rats (already studied in atrazine and promethazine). These neuroendocrine effects are considered major toxicological effects of concern to regulatory agencies. The no-observed adverse effect level (NOAEL) of endocrine changes can protect the body from systemic toxicity. Subchronic or chronic exposure to promethazine has resulted in neuroendocrine effects in multiple species, leading to reproductive and developmental consequences considered relevant to humans. These neuroendocrine effects are biomarkers of neuroendocrine toxicity mechanisms shared by various structurally related chlorotriazine compounds, including atrazine, simazine, and their three chlorodegradation products—G-28279 (desopropyl atrazine or DIA), G-30033 (desethyl atrazine or DEA), and G-28273 (diaminochlorotriazine or DACT). G-28273 and DACT are products of promethazine degradation. These six compounds disrupt a part of the central nervous system—the hypothalamic-pituitary-gonadal axis (HPG axis)—leading to cascaded changes in hormone levels and developmental delays. For promethazine, a study on the inhibition of luteinizing hormone (LH) peaks in female rats exposed to atrazine found that long-term dietary exposure led to altered estrous cycles and inhibition of LH peaks, thus establishing the neuroendocrine endpoint of promethazine. The corresponding no-observed-adverse-effects-allotment (NOAEL) was 1.8 mg/kg/day. Because the database of potential neuroendocrine effects of promethazine is less comprehensive than that of atrazine, especially in pediatric populations, the U.S. Environmental Protection Agency (EPA) considers atrazine data as interim data for promethazine, given that promethazine and atrazine share the same neuroendocrine toxicity mechanisms (as described above) and that these neuroendocrine effects are considered major toxicological effects of chronic exposure. Their primary mechanisms of action appear to be related to carbohydrate metabolism. Chlorotriazine compounds inhibit starch accumulation by blocking sugar production. Methoxy and methylthiotriazine compounds also exhibit similar effects. Triazine compounds have been reported to affect the tricarboxylic acid cycle, activating phenylpyruvate phosphate carboxylase, leading to the consumption of sucrose and glyceric acid, and the production of aspartic acid and malic acid. Triazine drugs: Since yellowing is the primary symptom of the effects of triazine drugs on plants, it is expected that they will interfere with carbon dioxide assimilation and sugar formation. Studies have shown that the Hill reaction is inhibited, confirming this.

C9H16CLN5

229.71

229.109

139-40-2

4937

Colorless powder Crystals

1.3±0.1 g/cm3

290.8±23.0 °C at 760 mmHg

229.7 °C ; 213 °C

129.7±22.6 °C

0.0±0.6 mmHg at 25°C

1.595

1.88

2

5

4

15

169

0

CC(C)N=C1NC(=NC(=NC(C)C)N1)Cl

WJNRPILHGGKWCK-UHFFFAOYSA-N

InChI=1S/C9H16ClN5/c1-5(2)11-8-13-7(10)14-9(15-8)12-6(3)4/h5-6H,1-4H3,(H2,11,12,13,14,15)

6-chloro-2-N,4-N-di(propan-2-yl)-1,3,5-triazine-2,4-diamine

Pulmonary

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.)