Phenergan and Pregnancy
Promethazine is a synthetic drug which is a derivative of phenothiazine, and refers to antihistamines of I generation, for oral and parenteral use.
Promethazine is a synthetic drug which is a derivative of phenothiazine, and refers to antihistamines of I generation. The mechanism of action of the drug is a selective blocking of histamine H1 receptors, as well as blocking cholinergic receptors and α-adrenergic receptors. Promethazine may also block histamine H3 receptors, which are located in the central nervous system. The drug has anti-allergic, anti-inflammatory, anesthetic effect and reduces exudative manifestations.
Promethazine has a strong sedative, antipsychotic, sedative effect and reduces body temperature. In addition, the drug reduces the excitability of the vestibular receptors, inhibits the function of the labyrinth, reduces dizziness and has antiemetic effect. According to their chemical structure, as well as pharmacological properties it is similar to other derivatives of phenothiazine – chlorpromazine.
Promethazine is well absorbed in both oral and parenteral use. Effect of the drug begins after 3-5 minutes after injection, 20 minutes after administration and after 15-60 minutes after taking inside the promethazine. The drug lasts for 4-6 hours and after oral administration can last up to 12 hours. The drug is a well associated with plasma proteins.
Promethazine well penetrates the blood-brain barrier. Promethazine passes through the placental barrier and is excreted in breast milk. The drug is metabolized in the liver, partially also in the kidneys. Promethazine is excreted primarily by the kidneys, partly excreted in the feces. Excretion period is 7-14 hours, with disruption of liver and kidney function this time can be increased.
Promethazine is used in allergic diseases (urticaria, angioedema, serum sickness), skin diseases (eczema, neurodermatitis, diathesis, prurigo, contact dermatitis, and drug reaction, allergic dermatitis), allergic reactions to drugs, motion sickness, Meniere's disease, vertigo, nausea and vomiting, hay fever, insect bites, anaphylactic and anaphylactoid reactions, allergic conjunctivitis and rhinitis, anxiety, neuroses and psychoses, extrapyramidal disorder, trigeminal neuralgia, fever and hyperthermia, rheumatism with severe allergic component, asthmatic bronchitis and bronchial asthma. In anesthesia may be used for sedation in the postoperative period as a sedative, to potentiate anesthesia and local anesthesia and artificial hibernation. Promethazine can be used in the examination of gastric juice as a stimulant for the secretion of histamine.
When applying promethazine following side effects may occur:
- Allergic reactions – rarely rash, urticaria, angioedema, contact dermatitis, photosensitivity, anaphylactic reactions.
- From the digestive system – often numbness of the oral mucosa, dry mouth, nausea, constipation or diarrhea; rarely jaundice.
- From the nervous system – often drowsiness, dizziness, restlessness, weakness, fatigue, incoordination, blurred vision; rarely euphoria, insomnia, seizures, catatonic state, hysteria, agitation, headache, loss of consciousness, nystagmus.
- Cardiovascular system – rarely tachycardia, bradycardia, by intravenous administration – an arterial hypotension, arrhythmia.
- Other adverse reactions – rarely difficulty in breathing, urinary retention.
- Changes in laboratory analysis – rarely leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia.
- Local reactions – not often painful, formation of infiltrates with the introduction; when administered intravenously or randomly in blood and subcutaneously may be experienced severe tissue damage (including gangrene and necrosis of tissues, including the necessity of skin grafts or amputation of the affected area).
According to the FDA reservations when using promethazine in standard therapeutic doses in children under 2 years are often observed respiratory depression which can be fatal.
Promethazine is contraindicated in case of hypersensitivity to phenothiazine derivatives, while the use of inhibitors during pregnancy and lactation, liver or kidney failure, alcohol intoxication, patients in a coma. Promethazine is contraindicated in children under 2 years of age and is used with caution in children under 6 years. The drug is carefully used in urinary retention, prostate cancer, peptic ulcer, diseases of the cardiovascular and nervous systems.
Forms of Issue
Promethazine is available as tablets of 0.005; 0.01 and 0.025g pellets to 0.025 g and 0.05 g of 2 ml vials of 2.5 % solution; powder in vials for injection of 0.05 g. Promethazine is available in combination with acetaminophen and dextromethorphan under the tradename «Coldrex Nite».
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