What Is Promethazine?

Promethazine can competitively block the histamine Hl receptor and produce an antihistamine effect. It can fight the telangiectasis caused by histamine, reduce its permeability, and relieve wheezing caused by the contraction of bronchial smooth muscle. Raming is strong and long lasting. Because it is easier to enter the brain tissue, it has a significant sedative effect; it can strengthen the central inhibitory effect of hypnotics, analgesics and anesthetics; its anticholinergic effect is also strong, and the effect of preventing motion sickness is better. For skin and mucous membrane allergies, allergic rhinitis, asthma, food allergies, skin scratches, motion sickness, seasickness, airsickness, etc.

Chinese name: Promethazine
Foreign name: Promethazine Hydrochloride Injection
Drug Name: Promethazine Hydrochloride Injection

Chemical Name: 10H-phenothiazine-10-ethylamine hydrochloride
Molecular formula: C17H20N2S
Alias: Finnagan, Amine Resistant

Promethazine compounds

Promethazine Basic Information

Chinese name: Promethazine

Chinese aliases: phenagen; phenagen; amine-resistant net; promicycline hydrochloride; aprodine; promethazine; promethazine; phenagen

English name: promethazine

English alias: Fenazil; Fargan; Prorex; 10H-Phenothiazine-10-ethanamine, N, N, -trimethyl-; WY 509; Phenergan

CAS number: 60-87-7

Molecular formula: C ₁₇ H ₂₀ N ₂ S

Structural formula:

Molecular weight: 284.41900

Exact mass: 284.13500

PSA: 31.78000

LogP: 4.30440

Promethazine physical and chemical properties

Density: 1.131

Melting point: 60ºC

Boiling point: 190-192ºC at 3 mm Hg

Promethazine Safety Information

Customs code: 2934300000 ^[1]

Promethazine production method

Add phenothia and base to toluene and heat to reflux for 1 h. Slightly cold, add 2-chloro-1-dimethylaminopropane in toluene solution, and reflux with water for 10-12h. Cool to below 50 ° C, filter the reaction solution, wash the filter residue with a small amount of acetone and water, wash the combined filtrate, leave it to stand, separate the toluene layer, recover the toluene by distillation under reduced pressure, collect the fraction at 220-260 ° C (1.33-2.66kPa), Promethazine (base) was obtained. The promethazine base was added to acetone, and a dry hydrogen chloride gas was passed through at about 50 ° C to carry out a salt formation reaction to generate the promethazine hydrochloride ^[1] .

Promethazine uses

Antihistamines. It is suitable for allergic diseases (such as asthma, urticaria, allergic rhinitis and bronchial asthma, etc.) and vomiting during pregnancy. It can also be combined with chlorpromazine to form a hibernation mixture for artificial hibernation ^[1] .

Promethazine Drug Description

Promethazine Pharmacology and Toxicology

Promethazine is a phenothiazine antihistamine, and is also used for antiemetics, anti-stuns, and sedative hypnosis.

(1) Anti-histamine effect: Competing with the histamine released by tissues for H1 receptors, it can antagonize the contraction or contraction of histamine on the gastrointestinal tract, trachea, bronchus or bronchiolar smooth muscle, and relieve the spasm and bronchial smooth muscle Congestive effect.

(2) Antiemetic effect: It may be related to the chemoreceptive area of emetic medulla which inhibits the medulla oblongata.

(3) Sedative and hypnotic effects: May be due to indirectly reducing the stress of the brainstem reticular activation system.

Promethazine pharmacokinetics

After injection, the absorption is fast and complete, and the plasma protein binding rate is high. After intramuscular injection, the onset time is 20 minutes, and after intravenous injection is 3 to 5 minutes, the antihistamine effect generally lasts for 6 to 12 hours, and the sedative effect can last for 2 to 8 hours. It is mainly metabolized in the liver, inactive metabolites are excreted through urine, and less excretion through feces.

Promethazine indications

(1) Allergies to skin and mucous membranes: Suitable for long-term, seasonal allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis, urticaria, angioedema, allergic reactions to blood or plasma products, skin scratches disease.

(2) Motion sickness: prevent motion sickness, seasickness, and airsickness.

(3) Adjuvant treatment before and after anesthesia and surgery, including sedation, hypnosis, analgesia, and antiemetic.

(4) Used to prevent radiation sickness or drug-induced nausea and vomiting.

Promethazine dosage

Intramuscular injection: Adult dosage

(1) Anti-allergic, 25mg once, repeated after 2 hours if necessary; 25 ~ 50mg can be injected intramuscularly in severe allergies, the maximum amount should not exceed 100mg.

(2) In special emergency situations, it can be diluted to 0.25% with sterile water for injection and slowly injected intravenously;

(3) Antiemetic, 12.5-25mg, repeated every 4 hours if necessary;

(4) Sedation and hypnosis, 25 to 50 mg at a time.

Pediatric commonly used amount

(1) Anti-allergic, every time according to body weight 0.125mg / kg or body surface area 3.75mg / m2, every 4 to 6 hours;

(2) Anti-dizziness, which can be given as needed before bedtime, based on body weight of 0.25 to 0.5 mg / kg or body surface area of 7.5 to 15 mg / m2. Or 6.25 12.5mg once a day, three times a day;

(3) Antiemetic, each time according to body weight 0.25 0.5mg / kg or body surface area 7.5 15mg / m2, repeated every 4-6 hours if necessary; or 12.5-25mg each time, repeated every 4-6 hours if necessary ;

(4) Sedation and hypnosis, if necessary, press 0.5 to 1 mg / kg of body weight or 12.5 to 25 mg each time.

Promethazine adverse reactions

Promethazine is a phenothiazine derivative. It has no obvious side effects at low doses, but common side effects of phenothiazines can occur during large and prolonged use.

(1) More common are drowsiness; less common are blurred vision or color blindness (mild), dizziness, dry mouth, nose, throat, tinnitus, rash, stomach pain or upset, unresponsiveness (most common in children), Fainting (hypotension), nausea or vomiting (when undergoing surgery and / or with other drugs), and even jaundice.

(2) Increase skin sensitivity to light, nightmares, irritability, excitability, hallucinations, toxic delirium, and children are prone to extrapyramidal reactions. The above reaction rate is not high.

(3) Cardiovascular adverse reactions are rare, showing increased blood pressure and occasionally a slight decrease in blood pressure. Leukopenia, agranulocytosis, and aplastic anemia are rare.

Promethazine precautions

(1) People who are known to be highly allergic to phenothiazines are also allergic to this product.

(2) The following conditions should be used with caution: acute asthma, bladder and neck obstruction, bone marrow suppression, cardiovascular disease, coma, angle-closure glaucoma, liver insufficiency, hypertension, gastric ulcers, those with obvious prostate hypertrophy symptoms, pylorus or ten Duodenal obstruction, respiratory diseases (especially children, thick sputum after taking this product, which affects sputum excretion, and can suppress cough reflex), patients with epilepsy (injection can increase the severity of convulsions), jaundice, Various liver diseases and renal failure, Reye syndrome (extrapyramidal symptoms caused by promethazine are easily confused with Reye syndrome). When using promethazine, special attention should be paid to intestinal obstruction, drug overdose, poisoning and other problems, because its symptoms and signs can be masked by promethazine's antiemetic effect.

Medication for pregnant and lactating women

(1) Pregnant women can induce jaundice and extrapyramidal symptoms in infants after using this medicine. Therefore, pregnant women should stop using this medicine 1-2 weeks before labor.

(2) The advantages and disadvantages of lactating women should be weighed when applying this product.

Medication for children

General antihistamines have a greater risk to babies, especially newborns and premature babies; infants less than 3 months of age have insufficient drug metabolism enzymes and should not use this product. It may also cause renal insufficiency. Neonatal or premature babies, children with acute illness or dehydration, and children with acute infections are prone to dystonia after injection of promethazine.

Medication for elderly patients

The elderly are prone to dizziness, stagnation, insanity, and hypotension with this medicine. It is also prone to extrapyramidal symptoms, especially Parkinson's disease, akathisia, and persistent dyskinesia. It is more likely to occur when used in large amounts or parenterally.

Promethazine Drug Interactions

(1) Disturbance to diagnosis: Glucose tolerance test can show increased glucose tolerance. Can interfere with urinary pregnancy immunity tests with false-positive or false-negative results.

(2) Ethanol or other central nervous system inhibitors, especially narcotics, barbiturates, monoamine oxidase inhibitors or tricyclic antidepressants, can increase the effect of promethazine or (and) these drugs when used with this product , Dosage should be adjusted separately.

(3) When anticholinergics, especially atropine and promethazine are used together, the latter has an increased antimuscarinic effect.

(4) When antihypertensive drugs such as benzyl bromide and guanethidine are used together with promethazine, the antihypertensive effect of the former is enhanced. When epinephrine and promethazine are used together, the alpha effect of adrenaline can be blocked, making the beta effect dominant.

(5) When ototoxic drugs such as cisplatin, paromomycin and other aminoglycoside antibiotics, salicylic acid preparations and vancomycin are used with promethazine, the ototoxic symptoms can be masked.

(6) It should not be mixed with aminophylline for injection.

Promethazine poisoning

Promethazine, also known as phenagen, is a phenothiazine antihistamine, which has an antihistamine effect; its effect is longer than that of diphenhydramine. It acts on the vestibular and vomiting centers and midbrain medulla receptors to treat motion sickness; it also has a sedative and hypnotic effect. Oral fast onset, half-life 7 ~ 16h. For allergic rhinitis, urticaria, conjunctivitis and other allergic diseases. At the same time can enhance the role of anesthetics, hypnotics, analgesics and local anesthetics. Adults usually use 12.5 25mg, 2 3 / d. The incidence of adverse reactions during hypnosis is 25% to 60%. Toxicity generally occurs after ingestion of 3 to 5 times the usual daily amount. Children are more sensitive.

Clinical manifestation

1. Common adverse reactions are drowsiness and drowsiness, fatigue, dizziness, tinnitus, ataxia, diplopia, euphoria, irritability, snoring, etc. Rarely, nausea, vomiting, and even jaundice occur. Cardiovascular reactions may have elevated blood pressure and occasionally a slight decrease in blood pressure.

2. Excessive amount of clumsy hands and feet. In severe cases, drowsiness or flushing, fever, dry mouth and nose, dyspnea, rapid heartbeat, muscle spasm (prone to spasmodic twitching of neck, back muscles, head muscles, or tremor of hands). May be at risk for seizures.

3. Extrapyramidal symptoms occur when people use high doses, and children are more prone to extrapyramidal symptoms. Elderly people are prone to dizziness, insanity, sluggishness, hypotension, and extrapyramidal symptoms.

4. Allergic reactions, such as urticaria, asthma, and angioedema.

5. Occasionally leukopenia, granulocytopenia, and aplastic anemia.

6. As a suppository, rectal tingling or burning sensation can occur.

treatment

The main points of treatment for promethazine poisoning are:

1. Swallow activated charcoal immediately after overdose and monitor for 6 ~ 8h. Gastric lavage for large intakes.

2. Severe reactions are mainly symptomatic and supportive.

3. The treatment of hemoperfusion and hemodialysis can not clear the promethazine in the body.

Promethazine Expert Review

Sedative effect is good, this drug can be preferred for gastrointestinal urticaria. Promethazine is an H1 receptor antagonist and its chemical structure belongs to phenothiazines. Its antihistamine effect is longer than that of diphenhydramine and has a significant central stabilization effect, but it is weaker than chlorpromazine, and it also has extensive inhibition of the subcortical center, which can produce antiemetic and lower body temperature. Can enhance the effects of anesthetics, sedative hypnotics and analgesics. Ophthalmology is clinically used for skin and mucous membrane allergies, such as eyelid contact dermatitis and allergic conjunctivitis.

^[2-5]