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Promethazine chemical structure
|ATC code |
|Molecular weight||284.425 g/mol|
|Bioavailability||88% absorbed but after first-pass metabolism reduced to 25% absolute bioavailability|
|Metabolism||Hepatic glucuronidation and sulfoxidation|
|Elimination half-life||16-19 hours|
|Excretion||Renal and biliary|
|Routes of administration||Oral, rectal, IV, IM|
Promethazine is a first-generation H1 receptor antagonist antihistamine and antiemetic medication. It is a prescription drug in the United States, but is available over the counter in the United Kingdom, Switzerland, and many other countries (brand names Phenergan®, Promethegan®, Romergan, Fargan®).
Promethazine also has strong anticholinergic and sedative effects. Previously it was used as an antipsychotic, although it is generally not administered for this purpose now; promethazine has only approximately 1/10 of the antipsychotic strength of chlorpromazine.
Indications[edit | edit source]
- As sedative/hypnotic
- For preoperative sedation and to counteract postnarcotic nausea
- As antiallergic medication to combat hay fever, allergic rhinitis, etc. To treat allergic reactions it can be given alone or in combination with oral decongestants like pseudo-ephedrine.
- Together with codeine or dextromethorphan against cough
- It can be used to increase the activity of opioids. It allows lower opioid doses and decreases their emetic properties.
- As a motion sickness or seasickness when used with Ephedrine or Pseudoephedrine.
- As an antipruritic (pruritus vulvae).
- To combat moderate to severe morning sickness and hyperemesis gravidarum.
Contraindications[edit | edit source]
- Promethazine should not be given to children under two years of age; there is potential for fatal respiratory depression in this age group.
- Hypersensitivity to Phenothiazines
- Closed angle glaucoma
- Intoxication with alcohol or other central depressants
- Severe hypotension or shock
- Coma due to any reason
- Severely impaired liver function
- Urine hesitancy due to enlargement of the prostate gland
Side effects[edit | edit source]
Typical side effects are:
- Blurred vision
- Confusion in the elderly
- Drowsiness, dizziness, fatigue, more rarely vertigo
- Dry mouth
- Seizures (extremely rare)
- Malignant neuroleptic syndrome (extremely rare)
- Respiratory depression in patients under age of 2 and in those with severely compromised pulmonal function
Dosage[edit | edit source]
Depending on disease and clinical condition (age, liver function):
- Mild to moderate cases of agitation: 25–50 mg orally, 3 to 4 times daily
- Insomnia: depending upon severity, 25–100 mg orally at bedtime
In pediatric patients doses as low as 5–10 mg, 3 times daily may suffice. For precise dosing syrup forms exist.
As an anti-emetic:
- Adult: 6.25 mg IV, or 12.5 mg IM
- Pediatric (greater than 2 years old): 0.25 mg/kg IV/ IM
Laboratory examinations[edit | edit source]
All patients should have their blood pressure measured frequently. During long-term therapy, blood cell counts, liver function studies, EKG, and EEG are recommended. The intervals should be determined according to the risk profile of the patient.
Recreational use[edit | edit source]
Promethazine is sometimes used as a recreational drug in conjunction with Codeine in prescription cough syrup. The mixture of Sprite and cough syrup with codeine is popularized in the rap world, especially in the Houston area.[How to reference and link to summary or text]
[edit | edit source]
- Letter from Wyeth Pharmaceuticals to practitioners regarding use of Phenergan in under twos. (PDF format)
References[edit | edit source]
- Basic and Clinical Pharmacology, 9th ed (2004). Katzung, Bertram G. pp. 264–265.
(Acrivastine) (Astemizole) (Azelastine) (Brompheniramine) (Carbinoxamine) (Cetirizine) (Chlorphenamine) (Clemastine) (Desloratadine) (Dimenhydrinate) (Diphenhydramine) (Doxylamine) (Loratadine) (Fexofenadine) (Meclizine) (Promethazine) (Triprolidine)
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