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Cimetidine(CAS No. 51481-61-9)

Cimetidine C10H16N6S (cas 51481-61-9) Molecular Structure

51481-61-9 Structure

Identification and Related Records

【CAS Registry number】
Cimetidine Type A/ AB
cimetidine A/AB
FPF 1002
Cimetidin AB
Cimetidine Form AB
Cimetidine Type AB/Type A
Guanidine, N-cyano-N-methyl-N-(2-(((5-methyl-1H-imidazol-4-yl)methyl)thio) ethyl)-
Guanidine, N-cyano-N-methyl-N-[2-[[ (5-methyl-1H-imidazol-4-yl)methyl]thio] ethyl]-
【Molecular Formula】
C10H16N6S (Products with the same molecular formula)
【Molecular Weight】
【Canonical SMILES】
【MOL File】

Chemical and Physical Properties

White crystals with a slight sulfur-mercaptan odor.
【Melting Point】
【Boiling Point】
【Flash Point】
0.5 g/100 mL at 20℃
0.5 g/100 mL at 20 oC
No data.
【Storage temp】
【Computed Properties】
Molecular Weight:252.33924 [g/mol]
Molecular Formula:C10H16N6S
H-Bond Donor:3
H-Bond Acceptor:3
Rotatable Bond Count:7
Tautomer Count:6
Exact Mass:252.115715
MonoIsotopic Mass:252.115715
Topological Polar Surface Area:114
Heavy Atom Count:17
Formal Charge:0
Isotope Atom Count:0
Defined Atom Stereocenter Count:0
Undefined Atom Stereocenter Count:0
Defined Bond Stereocenter Count:0
Undefined Bond Stereocenter Count:0
Covalently-Bonded Unit Count:1
Feature 3D Acceptor Count:1
Feature 3D Donor Count:3
Feature 3D Cation Count:2
Feature 3D Ring Count:1
Effective Rotor Count:7
Conformer Sampling RMSD:1
CID Conformer Count:160

Safety and Handling

【Hazard Codes】
【Risk Statements】
【Safety Statements 】

Hazard Codes:?ToxicT,HarmfulXn
Risk Statements: 60-42/43-36/37/38-20/22?
R60:May impair fertility.?
R42/43:May cause sensitization by inhalation and skin contact.?
R36/37/38:Irritating to eyes, respiratory system and skin.?
R20/22:Harmful by inhalation and if swallowed.
Safety Statements: 53-26-36/37/39-45-36-22?
S53:Avoid exposure - obtain special instructions before use.
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.?
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection.?
S45:In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)?
S36:Wear suitable protective clothing.?
S22:Do not breathe dust.
WGK Germany: 3
RTECS of Cimetidine (CAS NO.51481-61-9): MF0035500

【Exposure Standards and Regulations】
Manufacturers, packers, and distributors of drug and drug products for human use are responsible for complying with the labeling, certification, and usage requirements as prescribed by the Federal Food, Drug, and Cosmetic Act, as amended (secs 201-902, 52 Stat. 1040 et seq., as amended; 21 U.S.C. 321-392).

? Cimetidine (CAS NO.51481-61-9), its Synonyms are 1-Cyano-2-methyl-3-(2-(((5-methyl-4-imidazolyl)methyl)thio)ethyl)guanidine ; 2-Cyano-1-methyl-3-(2-(((5-methylimidazol-4-yl)methyl)thio)ethyl)guanidine ; Acibilin ; Acinil ; Cimetag ; Cimetidina . It is white solid.

【Octanol/Water Partition Coefficient】
log Kow= 0.40 (measured)
【Disposal Methods】
SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Use and Manufacturing

【Use and Manufacturing】
Methods of Manufacturing

Reflux of N-cyano-s-dimethylguanidine and 5-methyl-4-[(2-aminoethyl)-thiomethyl] imidiazole in acetonitrile.
Reaction of 5-methyl-4-[(2-aminoethyl)-thiomethyl] imidiazole with cyanodithioimidocarbonic acid dimethyl ester which gives the isothiourea and then reaction with methylamine.
Refluxing N-methyl-N'-(2-((5-methyl-imidazole-4-yl)-methyl)thio)ethyl)-2-thiourea (metiamide) and lead cyanamide.
Consumption Patterns

Sales approximated $100 x 10+6/year as of mid-year 1977.

Competitive histamine H2-receptor antagonist which inhibits gastric acid secretion and reduces pepsin output

Biomedical Effects and Toxicity

【Biological Activity】
Widely used H 2 histamine antagonist which has more recently been described as an inverse agonist. Also a potent I 1 imidazoline binding site ligand.
【Pharmacological Action】
- Various agents with different action mechanisms used to treat or ameliorate PEPTIC ULCER or irritation of the gastrointestinal tract. This has included ANTIBIOTICS to treat HELICOBACTER INFECTIONS; HISTAMINE H2 ANTAGONISTS to reduce GASTRIC ACID secretion; and ANTACIDS for symptomatic relief.
- Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.
- Drugs that selectively bind to but do not activate histamine H2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood.
【Therapeutic Uses】
Adjuvants, Immunologic; Analgesics, Non-Narcotic; Anti-Ulcer Agents; Enzyme Inhibitors; Histamine H2 Antagonists
Cimetidine is a useful alternative to antacids in preventing aspiration pneumonitis during childbirth and elective surgical procedures. It is less useful than antacids during emergency surgery because of its slow onset of action. This drug had been given to prevent alkalosis in patients subjected to prolonged nasogastric aspiration, especially those secreting large amounts of acid, and to decrease ileostomy/jejunostomy output in the short bowel syndrome.
H2 antagonists profoundly lower basal & nocturnal secretion of acid & that stimulated by meals & other factors; they reduce both the pain & duodenal ulcer & the consumption of of antacids, & they hasten healing. Duodenal ulcers usually heal within 4 to 6 weeks of treatment, but 8 weeks is sometimes required. About 10% of patients do not respond in this period of time, & more prolonged treatment with H2 antagonists is then of questionable value. Although similar rates of healing can be achieved by the vigorous administration of antacids, H2 antagonists are more conveniently administered & lack pronounced effects on bowel motility. After successful treatment, ulcers recur within a year in about 50% of patients; this rate can be reduced to about 20% by administration of maintenance doses of an H2 antagonist once daily at bedtime. /H2 antagonist/
H2 antagonists also accelerate the healing of benign gastric ulcers; treatment for 8 weeks is sufficient for 50 to 75% of patients. The drugs also markedly reduce the rate of relapse when given in maintenance doses at bedtime. /H2 antagonists/
H2 antagonists protect experimental animals from gastric ulceration induced by stress, pyloric ligation, aspirin, H2 antagonists, or cholinomimetics. H2 antagonists also counter peptic ulceration in man ... . /H2 antagonists/
H2 antagonists may be useful whenever it is appropriate to reduce gastric acid secretion. Such conditions include reflux esophagitis, stress ulcers, short-bowel (anastomosis) syndrome, & hypersecretory states associated with systemic mastocytosis or basophilic leukemia with hyperhistaminemia. They are also used as a preanesthetic medication in emergency operations to reduce the danger of aspiration of acidic gastric contents. /H2 antagonists/
Cimetidine is used in combination with an antihistamine to treat acute urticaria. /NOT included in US or Canadian product labeling/
Histamine H2-receptor antagonists are indicated in the short-term treatment of active duodenal ulcer. They are also indicated (at reduce dosage) in the prevention of duodenal ulcer recurrence in selected patients. /Histamine H2-receptor antagonists; Included in US product labeling/
Cimetidine ... /is/ indicated in the short-term treatment of active benign gastric ulcer. /Included in US product labeling/
Cimetidine ... /is/ indicated in the treatment of pathological gastric hypersecretion associated with Zollinger-Ellison syndrome (alone or as part of multiple endocrine neoplasia Type-1), systemic mastocytosis, and multiple endocrine adenoma. /Included in US product labeling/
Cimetidine ... /is/ indicated in the treatment of acute gastroesophageal reflux disease, which may or may not cause erosion or ulcerative esophagitis. /Included in US product labeling/
Cimetidine ... /is/ used to treat upper gastrointestinal bleeding secondary to gastric ulcer, duodenal ulcer, or hemorrhagic gastritis. /NOT included in US product labeling/
Histamine H2-receptor antagonists are not recommended for minor digestive complaints. /Histamine H2-receptor antagonists/
Cimetidine ... /is/ also used before anesthesia induction for the prophylaxis of aspiration pneumonitis. /NOT included in US product labeling/
... Cimetidine is indicated to prevent and used to treat upper gastrointestinal, stress-induced ulceration and bleeding, especially in intensive care patients. However, the efficacy of histamine H2-receptor antagonists in treating hemorrhage in critically ill patients has not been established. /Included in US product labeling/
In patients with pancreatic insufficiency, claims have been made that the reduction in hydrochloric acid secretion induced by cimetidine enhances the efficacy of oral pancreatic enzymes. However cimetidine is effective only in those with low rates of gastric acid secretion, and such patients rarely require this drug or other adjuvants. ... Cimetidine is ineffective in acute pancreatitis, and it may actually increase and prolong hyperamylasemia.
To attempt to reduce dapsone-dependent methemoglobinemia formation, 6 dermatitis herpetiformis patients (ages 31-86 yr), receiving individualized doses of dapsone, were treated with 400 mg cimetidine 3 times/day for 2 wk beginning 3 wk after the initiation of dapsone treatment. The incidence of methemoglobinemia due to dapsone decr by approx 27% within the first wk of initiating cimetidine treatment. The extent of dapsone-mediated control of dermatitis herpetiformis was unchanged. Plasma concn of monoacetyldapsone significantly incr while urinary excretion of dapsone hydroxylamine, the metabolite responsible for the hematological toxicity of dapsone, significantly decr during coadmin of cimetidine. It was concluded that coadmin of cimetidine may alleviate the hematological toxicity of dapsone without compromising drug efficacy. [Coleman MD et al; Br J Clin Pharmacol 34 (Sept): 244-249 (1992)]
【Biomedical Effects and Toxicity】
About 15% of cimetidine is metabolized in the liver. Seventy percent is excreted unchanged in the urine, with fecal losses accounting for approximately 10%.
Given orally, cimetidine and ranitidine are almost completely absorbed. Because of first-pass metabolism in the liver, the bioavailability is 50-60%. Both drugs are little bound to plasma proteins (10-20%).
Both drugs are mainly excreted in urine - cimetidine up to 90% within 24 hr (50-75% unchanged) and ranitidine up to 60% within 24 hr (about 40% unchanged). The apparent volume of distribution is quite large, in the range of 1.5 l/kg bw, demonstrating that nearly all drug exists outside the intravascular space.
Cimetidine is widely distributed throughout the body and is 15-20% bound to plasma proteins. Animal studies indicate that the drug crosses the placenta. Cimetidine is distributed into milk.
Studies show that following IV administration of radiolabeled cimetidine, 80-90% of the drug is excreted in urine within 24 hours; 50-73% is excreted unchanged and the remainder as the two metabolites /sulfoxide and 5-hydroxymethyl derivatives/. About 10% of the drug is excreted in feces. In one study, cimetidine was completely removed from the circulation after 5 hours of hemodialysis.
We examined the effects of varying maternal and fetal perfusion flow rates on the placental transfer of three model cmpd; antipyrine (high permeability), diclofenac (intermediate permeability), and cimetidine (low permeability) in the single-pass, dual-perfused lobule of the isolated human placenta. In variable flow ratio experiments (n = 9) fetal perfusate flow rate was held constant while a different maternal flow rate was used in each of five 25-min phases such that the maternal/fetal flow ratio ranged from 0.16 to 3.3. In constant flow ratio experiments (n = 4), the flow ratio was kept at 2.0, while maternal and fetal flow rates were varied from 4-18 and 2-9 ml/min, respectively. In the variable flow ratio experiments, the fetal transfer fraction (fetal venous/maternal arterial drug concn) varied approx fivefold among the five phases for each of the three drugs. Therefore, placental transfer was flow dependent regardless of placental drug permeability. By contrast, in the constant flow ratio experiments, fetal transfer fraction was unchanged throughout the five phases for each of the three drugs. Of the various kinetic models that have been formulated to account for the different possible vessel geometries, the double pool flow model, which is a venous equilibrium model and predicts the least efficient drug transfer rate of those proposed, together with a small maternal arteriovenous shunt, produced the best fit overall. [Bassily M et al; J Pharm Sci 84 (9): 1054-60 (1995)] PubMed Abstract
Uptake of the H2-receptor antagonist, cimetidine, into syncytial microvillus membrane vesicles of human term placenta was investigated to clarify whether an active transport mechanism can be responsible for the observed barrier of the human placenta for cimetidine. Imposition of an outwardly directed H(+)-gradient stimulated cimetidine uptake, resulting in a small transient overshoot. The H(+)-gradient-dependent peak uptake was decr under voltage-clamped conditions by carbonyl cyanide p-trifluoromethoxy-phenylhydrazone, suggesting the presence of an organic cation-proton exchange mechanism. Uptake was partially, but significantly, inhibited by organic cation transport inhibitors, H2-receptor antagonists and several other cationic drugs, providing further evidence for mediated uptake. H(+)-gradient-dependent cimetidine uptake was saturable and characterized by a low-affinity (Km) of 6.3 mM and Vmax of 17.5 nmol/mg protein/10 sec. We conclude that the system cannot play an important role in the barrier function of the human placenta in the transport of cimetidine. Rather than active transport, other factors, as for instance the degree of ionization of cimetidine at physiological pH, seem to be a more likely explanation for the low clearance of cimetidine across the human placenta. [Russel FG; J Pharmacol Exp Ther 276 (1): 219-22 (1996)] PubMed Abstract
Cimetidine concn in body tissues were pharmacokinetically examined, together with their postmortem changes, to assess the toxicological effect of this drug from the aspect of forensic medicine. for the pharmacokinetic study, rats were pithed at 0.5, 1.0, 2.0, 4.0 or 8.0 hr after an iv injection of the drug (33.3 mg/kg), and their tissue samples were immediately collected to be analyzed by HPLC. The concn of cimetidine in the blood and muscle decr below the lower detection limit at 8 hr after the injection, while the drug could still be detected in the brain, lung, liver, kidney, spleen and adipose tissue. The ratios of the cimetidine concn in the muscle, lung and spleen to that in the blood were nearly constant until 4 hr after the injection, while those in the liver, kidney, and adipose tissue incr as time elapsed. Postmortem changes of cimetidine concn were examined using the tissue samples collected 0, 1 and 2 days after death. There was no statistical significance in the postmortem changes in cimetidine concn in the body tissues over the 2-day period of exam. the experimental results indicated that the muscle, lung and spleen together can serve as samples for toxicological analysis to evaluate the effect of cimetidine, regardless of various postmortem factors, inc the availability of blood. [Imamura T et al; Nippon Hoigaku Zasshi 48 (2): 75-8 (1994)] PubMed Abstract
The effects of fasting-state gastrointestinal parameters on cimetidine absorption were examined using simulation studies and in dogs who received an iv injection of 10 mg/kg, duodenal infusion of 20 mg/kg, or oral tablets of 300-800 mg drug. Simulations indicated that double peaks occurred when gastric emptying of drug began in early phase I or late phase II/III, which represented low, medium, and high gastrointestinal motility, respectively. In dogs, a duodenal infusion in the active and quiescent motility phases resulted in discontinuous profiles. Mean input time tended to be higher for pH 6 infusions than for pH 4 or 8. The drug was more rapidly and completely absorbed at pH 8 than at pH 6. Bioavailability was also slightly higher at pH 4 than at pH 6. It was concluded that gastric emptying incr the variability of cimetidine concn-time profiles and plays a role in double-peak occurrence. [Langguth P et al; Biopharm Drug Dispos 15 (Dec): 719-746 (1994)] PubMed Abstract
To investigate cimetidine formulation effects on pilosebaceous unit deposition, several phospholipid liposomal, nonionic liposomal, alcohol, and aq formulations, of vary concn, were prepared and evaluated in vitro and in hamsters for cimetidine delivery to the pilosebaceous unit and other skin phases. No statistical differences were observed between the reductions of sebaceous gland area in the hamsters between the cimetidine formulations or control, but all were highly significant relative to placebo. In addition, cimetidine soln in the alcoholic and nonionic liposomal vehicles were active, but only at the local level. The phospholipid liposomal preparation proved to be inactive. It was concluded that cimetidine effects can be manipulated by drug concn and formulation. [Lieb LM et al; Pharm Res 11 (Oct): 1419-1423 (1994)] PubMed Abstract
The mechanisms and regional differences in absorption behavior and intestinal transport of cimetidine and ranitidine were investigated in rats. Results indicated that uptake of cimetidine and ranitidine in the rat jejunum and colon occurs by a predominantly passive process. Both drugs exhibited regional differences in uptake rate. Uptake tended to be greatest in the ileum, similar in duodenum and jejunum, and lowest in the colon. However, differences in uptake rates between locations in the small intestine appeared to be too modest to account for the double peak behavior of either compound.
The iv injection of cimetidine in a dose of 20 mg/kg enhanced verografine and iodamide excretion in chronic canine experiments. The higher verografine and iodamide excretion was due to their incr renal tubular secretion. In dogs, cimetidine unchanged the secretion of cardiotrast, a test agent for anionic transport. Possible extrarenal mechanisms of action of cimetidine on verografine and iodamide transport were also examined.
Freshly isolated proximal tubular cells of the rat are used to study the uptake of a prototypical organic cation, tetraethylammonium, and the influence of other cationic drugs on tetraethylammonium uptake. The time dependency of 50 uM tetraethylammonium uptake was determined by incubating proximal tubular cells for time periods from 10 sec until 60 min. Tetraethylammonium uptake was linear for at least 2 min and reached equilibrium after 30 min. The cell to medium ratio reached a value of 8 after 60 min, indicating marked accumulation of tetraethylammonium. Tetraethylammonium uptake was concentration dependent and saturable, with an apparent Km of 63 + or - 7 uM and Vmax of 0.57 + or - 0.02 nmol/mg protein.min. In comparison with cells cultured on filters, the overall transport characteristics of tetraethylammonium in PTC seem to resemble basolateral to apical flux. The concentration-dependent inhibition of some H2 antagonists and various cations on 32 uM tertaethylammonium uptake was investigated, as well as the interaction with probenecid. Analysis of the log-concentration inhibition curves showed that mepiperphenidol, trimethoprim, famotidine and cimetidine had a high and low IC50 value, whereas ranitidine, nizatidine, cimetidine sulfoxide, Nl-methylnicotinamide and probenecid had only a low IC50 value. The data reported here are comparable with those from other preparations, and it is possible to extrapolate to the human in vivo situation. Moreover, the isolation procedure is relatively simple and quick and the yield is high. [Boom SP et al; J Pharmacol Exp Ther 263 (2): 445-50 (1992)] PubMed Abstract
Female patients with a simple goiter were pretreated on 2 occasions (at an interval of 4 wk) with po placebo or 400 mg cimetidine (Group A, n = 10), or with placebo or 30 mg ranitidine (Group B, n = 101, 90 and 150 min, respectively, prior to the po gelatin capsules containing [125I]levothyroxine ([125I]levothyroxine. A double-blind randomized study protocol was kept. Venous blood samples were taken at 15, 30, 45, 60, 75, 90, 105, 120, 150, 180, 210, and 240 min after po [125I]levothyroxime and the radioactivities in serum were counted. Similar [125I]levothyroxine radioactivities were found after placebo pretreatment in both groups: AUC 467 + or - 82 in Group A vs 459 + or - 109 in Group B. Cimetidine decreased the serum [125I]levothyroxine radioactivities: AUC371 + or - 72 vs 467 + or - 82 (placebo) (P 0.05).[Jonderko G et al; Chung Kuo Yao Li Hsueh Pao 13 (5): 391-4 (1992)] PubMed Abstract

Environmental Fate and Exposure Potential

【Environmental Fate/Exposure Summary】
TERRESTRIAL FATE: Based on a recommended classification scheme(1), an estimated Koc value of 39(SRC), determined from an experimental log Kow(2) and a recommended regression-derived equation(3), indicates that cimetidine should have very high mobility in soil(SRC). However, cimetidine will exist in both the undissociated and cation form under environmental conditions (pH 5-9), (pKa of 6.8)(6); no experimental data are available to indicate whether the cation will adsorb to soil more strongly than its estimated Koc value for the undissociated form indicates(SRC). Volatilization of cimetidine should not be important from moist soil surfaces(SRC) given an estimated Henry's Law constant of 9.5X10-16 atm-cu m/mole(SRC), using a recommended regression equation(4) or from dry soil surfaces(SRC) based on an estimated vapor pressure of 5.5X10-9 mm Hg(SRC), using a fragment constant method(5). Insufficient data are available to determine the rate or importance of biodegradation of cimetidine in soil(SRC).
AQUATIC FATE: Based on a recommended classification scheme(1), an estimated Koc value of 39(SRC), determined from an experimental log Kow(2) and a recommended regression-derived equation(1), indicates that cimetidine would not adsorb to suspended solids and sediment(SRC) in the water. However, cimetidine will exist in both the undissociated and cation form under environmental conditions (pH 5-9), (pKa of 6.8)(5);no experimental data are available to indicate whether the cation will adsorb to soil more strongly than its estimated Koc value for the undissociated form indicates(SRC). Cimetidine will be essentially non-volatile from water surfaces based on an estimated Henry's Law constant of 9.5X10-16 atm-cu m/mole(SRC), developed using a fragment constant estimation method(3). An estimated BCF value of 1.2(1,SRC), from an experimental log Kow(2), suggests that cimetidine will not bioconcentrate in aquatic organisms(SRC), according to a recommended classification scheme(4). Insufficient data are available to determine the rate or importance of biodegradation of cimetidine in water(SRC).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), cimetidine, which has an estimated vapor pressure of 5.5X10-9 mm Hg at 25 deg C(2,SRC), will exist primarily in the particulate phase in the ambient atmosphere. Vapor-phase cimetidine is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be about 1.8 hours(3,SRC). Particulate-phase cimetidine may be physically removed from the air by wet deposition(SRC).

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