Basic information Description Clinical Pharmacology Indications and Usage Drug overdose Contraindications Safety Related Supplier
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Diphenhydramine Hydrochloride

Basic information Description Clinical Pharmacology Indications and Usage Drug overdose Contraindications Safety Related Supplier
Diphenhydramine Hydrochloride Basic information
Diphenhydramine Hydrochloride Chemical Properties
  • Melting point:168-172 °C
  • Boiling point:163-167 °C(Press: 3 Torr)
  • Density 1.0489 (rough estimate)
  • refractive index 1.5800 (estimate)
  • Flash point:9℃
  • storage temp. Desiccate at RT
  • solubility Very soluble in water, freely soluble in alcohol.
  • form Crystalline Powder or Adhering Crystals
  • color White
  • PHpH(100g/L, 25℃) 4.0~5.5
  • Water Solubility 1000 g/L
  • Sensitive Light Sensitive
  • Merck 14,3309
  • Stability:Stable, but slowly darkens upon exposure to light. Incompatible with strong oxidizing agents.
  • CAS DataBase Reference147-24-0(CAS DataBase Reference)
  • NIST Chemistry Referencediphenhydramine hydrochloride(147-24-0)
  • EPA Substance Registry SystemDiphenhydramine hydrochloride (147-24-0)
Safety Information
Diphenhydramine Hydrochloride Usage And Synthesis
  • DescriptionDiphenhydramine hydrochloride is an antihistamine drug having the chemical name 2-(Diphenylmethoxy)- N,N-dimethylethylamine hydrochloride. It occurs as a white, crystalline powder, is freely soluble in water and alcohol and has a molecular weight of 291.82.
    The molecular formula is C17H21NO·HCl and the structural formula is as follows:
    Diphenhydramine hydrochloride structural formula
    Diphenhydramine hydrochloride in the parenteral form is a sterile, pyrogen-free solution available in a concentration of 50 mg of diphenhydramine hydrochloride per mL. The solutions for parenteral use have been adjusted to a pH between 5.0 and 6.0 with either sodium hydroxide or hydrochloric acid and contains 0.1 mg/mL benzethonium chloride as a germicidal agent.
  • Clinical PharmacologyDiphenhydramine hydrochloride is an antihistamine with anticholinergic (drying) and sedative side effects. Antihistamines appear to compete with histamine for cell receptor sites on effector cells. Diphenhydramine hydrochloride in the injectable form has a rapid onset of action. Diphenhydramine hydrochloride is widely distributed throughout the body, including the CNS. A portion of the drug is excreted unchanged in the urine, while the rest is metabolized via the liver. Detailed information on the pharmacokinetics of Diphenhydramine Hydrochloride Injection is not available.
  • Indications and UsageDiphenhydramine hydrochloride in the injectable form is effective in adults and pediatric patients, other than premature infants and neonates, for the following conditions when diphenhydramine hydrochloride in the oral form is impractical.
    1. antihistaminic: For amelioration of allergic reactions to blood or plasma, in anaphylaxis as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled, and for other uncomplicated allergic conditions of the immediate type when oral therapy is impossible or contraindicated.
    2. Motion Sickness: For active treatment of motion sickness.
    3. Antiparkinsonism: For use in parkinsonism, when oral therapy is impossible or contraindicated, as follows: parkinsonism in the elderly who are unable to tolerate more potent agents; mild cases of parkinsonism in other age groups, and in other cases of parkinsonism in combination with centrally acting anticholinergic agents.
  • Drug overdoseAntihistamine overdosage reactions may vary from central nervous system depression to stimulation. Stimulation is particularly likely in pediatric patients. Atropine-like signs and symptoms; dry mouth; fixed, dilated pupils; flushing; and gastrointestinal symptoms may also occur. Stimulants should not be used. Vasopressors may be used to treat hypotension.
  • Contraindications
    1. Use in Neonates or Premature Infants: This drug should not be used in neonates or premature infants.
    2. Use in Nursing Mothers: Because of the higher risk of antihistamines for infants generally, and for neonates and prematures in particular, antihistamine therapy is contraindicated in nursing mothers.
    3. Use as a Local Anesthetic: Because of the risk of local necrosis, this drug should not be used as a local anesthetic.
    4. Antihistamines are also contraindicated in the following conditions: Hyper sensitivity to diphenhydramine hydrochloride and other antihistamines of similar chemical structure.
  • Chemical PropertiesWhite or almost white, crystalline powder.
  • UsesDiphenhydramine is a H1-histamine receptor antagonist. Diphenhydramine is categorized as an antihistaminic; sedative, hypnotic.
  • Usesantihistamine, sedative, treatment of allergic
  • UsesA histamine H1-receptor antagonist.
  • UsesH1-Histamine receptor antagonist. Antihistaminic; sedative, hypnotic
  • DefinitionChEBI: The hydrochloride salt of diphenhydramine.
  • brand nameBenadryl (Parke-Davis).
  • General DescriptionDiphenhydramine hydrochloride, 2-(diphenylmethoxy)- N,N-dimethylethanamine hydrochloride (Benadryl), is an oily, lipid-soluble free base available as the bitter-tasting hydrochloride salt, which is a stable, white crystalline powder soluble in water (1:1), alcohol (1:2) and chloroform (1:2). The salt has a pKa value of 9, and a 1% aqueous solution has a pH of about 5.
    In addition to antihistaminic action, diphenhydramine exhibits antidyskinetic, antiemetic, antitussive and antimuscarinic, and sedative properties.As an antihistaminic agent, diphenhydramine is recommended in various allergic conditions and, to a lesser as an antitussive and Parkinsonism drug. It is also used in OTC sleep-aid products. It is administered either orally or parenterally in the treatment of urticaria, seasonal rhinitis (hay fever), and some dermatoses.
  • General DescriptionWhite or almost-white crystalline powder. Odorless with a bitter numbing taste. pH (5% aqueous solution) 4-6.
  • Air & Water ReactionsWater soluble. Aqueous solutions are acidic.
  • Reactivity ProfileN-(2-Diphenylmethoxyethyl)-N,N-dimethylamine hydrochloride gives acidic solutions in water. Neutralizes bases. May react with strong oxidizing and strong reducing agents. May catalyze organic reactions. Slowly darkens on exposure to light.
  • Fire HazardFlash point data for N-(2-Diphenylmethoxyethyl)-N,N-dimethylamine hydrochloride are not available; however, N-(2-Diphenylmethoxyethyl)-N,N-dimethylamine hydrochloride is probably combustible.
  • Biological ActivityH 1 receptor antagonist. Antihistamine.
  • Contact allergensThis antihistaminic drug with sedative properties is mainly sold over the counter. It can be used both topically (treatment of pruritis) and orally for its antiallergic, antiemetic, sedative, and anticough properties. Allergic or photoallergic contact dermatitis and fixeddrug eruption seem to be rare.
  • Safety ProfilePoison by ingestion, subcutaneous, intravenous, and intraperitoneal routes. Human systemic effects by ingestion or skin contact: arrhythmias, ataxia, blood pressure elevation, convulsions, distorted perceptions, eye effects, and hallucinations. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental tumorigenic data. When heated to decomposition it emits very toxic fumes of NO, and HCl. See also ESTERS and ETHERS.
  • Veterinary Drugs and TreatmentsIn veterinary medicine, diphenhydramine is used principally for its antihistaminic effects, but also for other pharmacologic actions. Its sedative effects can be of benefit in treating the agitation (pruritus, etc.) associated with allergic responses. It has also been used for treatment and prevention of motion sickness and as an antiemetic in small animals. It has been suggested for use as adjunctive treatment of aseptic laminitis in cattle and it may be useful as an adjunctive treatment for feline pancreatitis. For other suggested uses, refer to the Dosage section below.
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