What Is Diphenhydramine?

Diphenhydramine, an antihistamine. It has an antihistamine H1 receptor effect, a strong inhibitory effect on the central nervous system, and an atropine-like effect. For skin and mucous membrane allergic diseases, such as urticaria, hay fever, allergic rhinitis, etc. It can also be used to prevent motion sickness such as seasickness, motion sickness, and aircraft motion sickness. Sleepiness and dry mouth are the main adverse reactions.

Chinese name: Diphenhydramine
Molecular formula: C17H21NO · HCl

Melting point: 167 171
Use: oral
Molecular weight: 291.82

Diphenhydramine compounds

Diphenhydramine Basic Information

Chinese name: diphenhydramine

Chinese alias: dibutylcarbamyl chloride; benajun; ketamin; benazine; benazine; benazine; ketamine

English name: N, N-dibutylcarbamoyl chloride

English alias: Carbamic chloride, 1,6-dibutyl; Dibutylcarbamyl chloride; dibutylcarbamic chloride; di-n-butyl-carbamic acid chloride; Carbamoyl chloride, dibutyl; Diphenhydramine; Benadryl; Rigidil; Benadryl

CAS number: 13358-73-1

Molecular formula: C ₉ H ₁₈ ClNO

Structural formula:

Molecular weight: 191.69800

Exact mass: 191.10800

PSA: 20.31000

LogP: 3.24740

Diphenhydramine Safety Information

Customs code: 2903199000 ^[1]

Diphenhydramine Drug Description

Diphenhydramine Classification

Antiallergic Drugs> Antihistamines

Diphenhydramine dosage form

1. Tablet: 25mg, 50mg;

2. Injection: 20mg (1ml);

3. Cream: 20g.

Pharmacological effects of diphenhydramine

It is a derivative of ethanolamine. Its antihistamine effect is less than that of promethazine, and the duration of action is also short. The sedative effect is the same for both drugs. There are also local anesthesia, antiemetic and anti-M-choline-like effects.

(1) Histamine action: It can compete with H1 released from tissues to H1 receptors on effector cells, thereby stopping allergic attacks;

(2) Sedative and hypnotic effects: The mechanism of inhibiting central nervous activity is not clear;

(3) Antitussive effect: it can directly act on the cough center of the medulla oblongata and inhibit cough reflex.

Diphenhydramine Pharmacokinetics

Oral absorption is complete, tmax is 2h, maintenance is 4-6h, elimination half-life is about 4h, protein binding rate is 78% -99%. 98% bound to plasma proteins. First pass metabolism in the liver. After oral administration, it reaches about 50% before reaching systemic circulation. It is widely distributed and can be distributed in the brain tissue through the blood-cerebrospinal fluid barrier; most of the liver is transformed in the form of metabolites from urine, stool, and sweat, and breastfeeding women can also excrete part of their milk. Diphenhydramine has a drug-enzyme-inducing effect and accelerates its own metabolism. Almost all discharged within 24h ^[2] .

Diphenhydramine indications

1. Skin and mucous membrane allergies, such as urticaria, angioedema, allergic rhinitis, other pruritus of the skin, pruritus of the anus, pruritus of the vulva, pruritus of medicinal rash or jaundice, also effective for insect bites and contact dermatitis ;

2. Acute allergic reactions can reduce allergic reactions caused by blood transfusion or plasma; Antihistamines such as diphenhydramine are often applied before blood transfusion. Diphenhydramine is usually given intramuscularly at a dose of 40 mg. Pay attention to the selection of donors Try not to use blood donors with a history of allergies. Avoid repeated infusions of blood from the same donors to avoid antigen-antibody reactions. For example, when anti-IgA antibodies are present in the recipient, washed red blood cells can be transfused. This washing method can remove IgA from the donor's blood. To prevent the occurrence of allergic reactions.

3. The prevention and treatment of motion sickness and seasickness has a strong antiemetic effect, and can also be used to prevent radiation sickness, postoperative vomiting, and nausea and vomiting caused by drugs;

4, for Parkinson's disease and extrapyramidal symptoms;

5. Sedation, used for hypnosis and preoperative administration;

6. Dental local anesthesia. When patients are highly allergic to common local anesthetics, 1% diphenhydramine solution can be used as dental local anesthesia;

7. Antitussive, as a non-addictive cough medicine, is suitable for the treatment of cough caused by colds or allergies, but its antitussive effect has not yet been confirmed.

8. Others, Xu Heding, Xue Shijian, Lu Xiaobing and others reported that taking diphenhydramine 50 mg daily before bedtime, and even taking 10 to 14 days to treat drooling symptoms caused by clozapine, safe and effective.

Diphenhydramine contraindications

1. Newborns, premature babies, early pregnant women, breastfeeding women, etc. are contraindicated.

2. Closed-angle glaucoma patients are disabled.

3. Prostatic hyperplasia, bladder neck obstruction, and intestinal obstruction are contraindicated.

4. Patients with pyloric and duodenal obstruction are disabled.

5. Myasthenia gravis is disabled.

6. Disabled before various skin tests ^[2] .

Diphenhydramine dosage

1. Adults take 25 to 50 mg orally 3 to 4 times a day. 1 to 5 years old children 12.5 to 25 mg, 3 to 4 times a day; 6 to 12 years old children 25 to 50 mg, 3 times a day, after meals Intramuscular injection and intravenous injection, 20mg each time, 1 to 2 times a day, 100mg once a day, 300mg a day. It can also be made into cream for external use to treat insect bites, neurodermatitis, vulvar pruritus, and various dermatitis skin diseases. Topical application 2 times a day.

2. When the glomerular filtration rate (GFR) is 10 ~ 50ml per minute, the interval between two administrations should be extended to 6 ~ 9h; when the <10ml per minute, the interval should be extended to 9 ~ 12h ^[2] .

Diphenhydramine precautions

1. Patients with bronchial asthma after taking diphenhydramine may make the sputum thick, make it difficult to cough up and aggravate breathing difficulties, which should be taken seriously.

2. Hypotension, hypertension, other cardiovascular diseases, hyperthyroidism, glaucoma patients should be used with caution.

3 Early pregnancy women, lactating women, newborns and premature infants are contraindicated.

4 Long-term application of this drug may cause hemolysis or hematopoietic dysfunction, especially for long-term injection.

5. Although antihistamines are anti-allergic drugs, they can also cause allergies. Diphenhydramine has cases of drug-induced allergic rash, so if the patient develops a rash during the medication, stop the drug or switch to other antihistamines.

6. Diphenhydramine, if used in combination with hypnotic, sedative, and tranquillizing drugs, or drinking at the same time, can aggravate central inhibitory effects and should be avoided.

7. Antihistamines often have rapid tachyphylaxis, or resistance reactions. For example, when diphenhydramine is used in patients with habitual allergic diseases, the initial efficacy is often very significant, but the effect gradually decreases with the extension of the medication time. When such a drug resistance reaction occurs, it is appropriate to switch to other types of antihistamines as soon as possible to prevent the development of drug resistance from affecting the efficacy.

8. Overdose can cause toxic reactions such as lethargy, palpitations, muscle tremors, blurred vision, confusion, and even convulsions. Gastric lavage, oxygenation, and convulsions should be given.

9. Old people are prone to stagnation or dizziness after taking medication for a long time.

10 In renal failure, the interval between dosing should be prolonged. The antiemetic effect of this product may cause difficulty in the diagnosis of certain diseases, such as appendicitis and some drug-induced poisoning.

11. This product can affect the conduction of neuromuscular junctions, and it is contraindicated in patients with myasthenia gravis.

Diphenhydramine adverse reactions

1. The most common are: stagnation, sleepiness, inattention, fatigue, dizziness, dizziness, ataxia, nausea, vomiting, loss of appetite, dry mouth, etc.

2. Rarely: shortness of breath, chest tightness, cough, dystonia, etc. It has been reported that after the administration of the teeth, tightness of the teeth can occur, with laryngospasm, anaphylactic shock, and arrhythmia. Excessive application can cause acute poisoning and mental disorders.

Diphenhydramine overdose

The toxicity of this product is mainly to make the central nervous system first inhibit, then excite, and finally produce exhaustive inhibition, the severity depends on the dosage. Once found to be taken by mistake or overdose, it should be immediately sent to the hospital for emergency treatment.

Appears as anorexia, nausea, vomiting, constipation or diarrhea, thirst, frequent urination or dysuria, hematuria, hearing impairment, blurred vision, dyskinesia, superficial breathing, tachycardia, fever and pain under the sternum; convulsions may occur in severe cases , Coma, cardiac depression, respiratory paralysis.

When rescued, they should be immediately taken to the hospital for vomiting, gastric lavage, catharsis, intravenous fluid replacement, oxygen inhalation, and symptomatic treatment. For patients with excitement, sedatives are generally not used except for convulsions, so as not to cause central depression. When convulsions occur, 10 to 15 ml of 10% chloral hydrate solution can be given to retain the enema, or thiopental sodium can be injected intravenously. When inhibition occurs, do not use a central stimulant. For those who are deeply inhibited, especially if it affects breathing, give a breathing stimulant as appropriate, but observe closely to prevent convulsions.

Diphenhydramine Drug Interactions

1. Combined with H2 histamine receptor blockers (cimetidine, etc.) can enhance the anti-allergic effect and achieve the effect of comprehensive block of histamine receptors.

2. Diphenhydramine has a significant anticholinergic effect, which can antagonize the miotic effect of cholinesterase inhibitors. The pupil dilatation effect is not obvious at normal doses, and there is no important interaction between the two, but sometimes diphenhydramine is applied. Ming can affect the treatment of glaucoma. The same use with monoamine oxidase inhibitors can enhance the anticholinergic effect of diphenhydramine, reduce the metabolism of diphenhydramine, and increase adverse reactions (enzyme inhibition).

3. Diphenhydramine can enhance the effects of central nervous system inhibitors (hypnosis, sedation, and tranquilizers), and should be avoided at the same time.

4. Diphenhydramine can treat extrapyramidal symptoms caused by two drugs, triflurazine and metoclopramide (metolin).

5. With the same use of sodium salicylate can reduce the intestinal absorption of the latter and reduce its blood concentration.

6. Diphenhydramine may cover streptomycin and other aminoglycoside antibiotics (gentamicin, kanamycin, amikacin, etc.) or other ototoxic drugs (such as itanilic acid) Ototoxicity.

7. A large dose of diphenhydramine can reduce the anticoagulant effect of heparin.

8. Diphenhydramine can antagonize the effects of adrenergic nerve blockers.

9. Diphenhydramine can temporarily affect the absorption of barbiturates and sodium sulfacetate.

10. When diphenhydramine is used together with alcohol, the damage to intelligence and athletic ability is greater than the single use. There are great individual differences in the degree of mutual influence after combined use. Drivers and operators of dangerous machines should avoid drinking alcohol while taking diphenhydramine.

11. Green tea can antagonize drowsiness, headache, dizziness and other adverse reactions caused by diphenhydramine.

12. Diphenhydramine is contraindicated with iodide and sodium phenobarbital ^[2] .

Diphenhydramine poisoning

Diphenhydramine is an ethanol-based antihistamine that can fight histamine or alleviate the effects of histamine on smooth muscles such as blood vessels, gastrointestinal and bronchi. It is suitable for allergic diseases of the skin and mucous membranes, and has a poor effect on bronchial asthma. Oral absorption is rapid and complete, with a half-life of 4 to 24 hours. It can pass the blood-brain barrier and has a strong inhibitory effect on the central nervous system. Adults usually use 25mg, 3 4 / d. Poisoning occurs 3 to 5 times the usual amount after ingestion; oral lethal dose is 20 to 40 mg / kg.

Clinical manifestation

1. Occasionally shortness of breath, chest tightness, cough, dystonia, etc. Throat spasms have been reported. Reports of a large number of taking cause ECS QRS broadening, QT interval prolongation, and myocardial depression.

2. Patients with conventional doses 36 to 40 times often experience symptoms such as mental abnormality, mental stiffness, anxiety; hallucinations, dilated pupils, and tachycardia. Rarely, diplopia, respiratory insufficiency, and seizures. Deaths from hypothermia have been reported.

3. Loss of directional power, agitation, dilated pupils, unresponsiveness, and ataxia.

treatment

The main points of treatment for diphenhydramine poisoning are:

1. A large number of people who take oral gastric lavage and activated charcoal in time.

2. No specific antidote, mainly symptomatic treatment.

3. For patients with altered QRS and QT intervals, intravenous infusion of 5% sodium bicarbonate may be effective ^[3] .

Diphenhydramine Expert Reviews

Diphenhydramine is an ethylenediamine antihistamine. Can fight or reduce the effects of histamine on blood vessels, gastrointestinal and bronchial smooth muscle. It is suitable for allergic diseases of the skin and mucous membranes, creams for external use to control insect bites, neurodermatitis, pruritus and so on. It has a good effect on urticaria, but has a strong central inhibitory and anticholinergic effect, which causes a strong sedative effect. Do not exercise immediately after intramuscular or intravenous injections. Drive the vehicle to prevent fainting. It can be administered flexibly at night or Medication before going to bed. It is mainly used in the treatment of Parkinson's disease to relieve symptoms. Because diphenhydramine inhibits the central system, it is currently less commonly taken orally and is often made into dermal preparations for local anti-allergy. Topical diphenhydramine has been reported to cause allergic dermatitis ^[2] .

Diphenhydramine Hydrochloride Tablets

Common name: Diphenhydramine hydrochloride tablets

English name: Diphenhydramine Hydrochloride Tablets

Phonetic script (Hanyu Pinyin): Yansuan Benhailaming Pian

The main ingredients and chemical name of this product are: N, N-dimethyl-2- (diphenylmethoxy) ethylamine hydrochloride

Its structural formula is:

C ₁₇ H ₂₁ NO · HCl 291.82

[Character]

This product is a sugar-coated tablet, which appears white after removing the sugar coating.

[Pharmacology and Toxicology]

It is a derivative of ethanolamine. Its antihistamine effect is less than that of promethazine, and the duration of action is short. The sedative effect is the same as the two drugs. It has local anesthesia, antiemetic and anti-M choline-like effects. (1) Anti-histamine effect, can compete with H1 released from tissues to effect H1 receptors on effector cells, thereby stopping allergic reactions; (2) Inhibition of central nervous activity causes sedative and hypnotic effects; (3) Strengthening sedation Cough medicine effect; (4) also has anti-vertigo, anti-tremor paralysis effect.

Pharmacokinetics

Oral absorption is fast and complete, with a plasma protein binding rate of 98%, peak plasma concentration in 1 to 4 hours, and T1 / 2 in 4 to 7 hours. The drug can enter the center through the blood-brain barrier. It takes effect 15 to 60 minutes after oral administration, and can be maintained for 3 to 6 hours after a single administration.

[Indications]

Mainly used for: skin and mucous membrane allergies, such as urticaria, angioedema, allergic rhinitis, pruritus skin, drug rash, also effective for insect bites and contact dermatitis; prevention and treatment of motion sickness, strong antiemetic Action; Parkinson's disease and extrapyramidal symptoms; sedation, hypnosis; strengthen the effect of antitussives, suitable for the treatment of cough caused by colds or allergies.

Dosage

Adults usually take orally after meals, 25 to 50 mg, 2 to 3 times a day.

[Dosing Instructions]

When used to prevent motion sickness, it should be taken 1 to 2 hours before travelling, and at least 30 minutes before taking.

Adverse reactions

(1) Common are: central nervous system inhibitory effect, ataxia, nausea, vomiting, and loss of appetite. (2) Rarely: shortness of breath, chest tightness, cough, dystonia, etc. It has been reported that the teeth can be closed tightly with laryngospasm after administration. (3) Occasionally can cause rash, granulocytopenia, anemia and heart rate disturbance.

Contraindications

Myasthenia gravis, angle-closure glaucoma, and prostatic hypertrophy are contraindicated.

Those who are allergic to this product and excipients are prohibited. Newborn and premature infants are disabled.

Precautions

(1) Pyloric duodenal obstruction, pyloric stenosis due to peptic ulcer, bladder neck stenosis, hyperthyroidism, cardiovascular disease, hypertension and lower respiratory infections (including asthma) should not be used. (2) Those who are highly allergic to other ethanolamines may also be allergic to this product. (3) Avoid driving vehicles, working at height or operating machines after applying this medicine. (4) In the case of renal failure, the interval between administrations should be extended. (5) The antiemetic effect of this product may cause difficulty in the diagnosis of certain diseases.

[Medication for pregnant and lactating women]

(1) Taking this product during pregnancy may increase the incidence of cleft palate, inguinal hernias and genitourinary organ deformities, and pregnant women should use it with caution; (2) A small amount of this product can be excreted from breast milk and should not be used by breastfeeding women.

[Child medication]

[Medication for elderly patients]

Slow response, dizziness, etc. can occur.

medicine interactions

(1) This product can temporarily affect the absorption of barbiturates and sodium sulfacetamide. (2) The same use with p-aminosalicylic acid can reduce the blood concentration of the latter. (3) can enhance the role of central nervous system inhibitors.

[Drug overdose]

Overdose may cause confusion, convulsions, tremors, dyspnea, and hypotension. Overdose in infants and children can cause agitation, hallucinations, convulsions, and even death. If you take a toxic amount, you can use gastric lavage and catharsis. Diazepam can be controlled while convulsing. Hypotension can be treated symptomatically with vasoconstrictors. Others include oxygen and intravenous fluids and supportive care.

specification

25mg

Storage

Keep sealed. ^[4]