is a first-generation H1 receptor
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
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.
Chemically, promethazine hydrochloride (HCl) appears as a white to faint yellow crystaline powder which is practically odorless. Slow oxidation may occur upon prolonged exposure to air causing blue discoloration. Promethazine as the hydrochloric salt is freely soluble in water and somewhat soluble in alcohol.
- 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
Mechanism of action
- Promethazine is a phenothiazine derivative that competitively blocks histamine H1 receptors without blocking the secretion of histamine.
- It has sedative, anti-motion-sickness, anti-emetic, and anti-cholinergic effects
- However, unlike other phenothiazines, it has no dopaminergic action due to a structural difference with other phenothiazines.
Some common side effects include:
- Blurred vision
- Confusion in the elderly
- Drowsiness, dizziness, fatigue, more rarely vertigo
- Dry mouth
- Seizures (extremely rare)
- Neuroleptic malignant syndrome (extremely rare)
- Respiratory depression in patients under age of 2 and in those with severely compromised pulmonal function
- Euphoria (very rare with high IV doses and/or coadministration with opioids/CNS depressants)
- Restless legs
When incorrectly administered parenterally, severe reactions requiring immediate medical attention include:
It is recommended that Promethazine only be given through an existing intravenous set in a large vein, and diluted to concentration no greater than 25mg per ml, not to exceed a rate of administration of 25mg a min. Serious complications including those listed above have resulted from improper parenteral administration, including those requiring surgical intervention and amputation.
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.
In high doses Promethazine can create auditory and visual hallucinations causing panic and intense fear. If mixed with alcohol less needs to be taken to get these effects therefore can really take someone by surprise.
Promethazine is sometimes used as a recreational drug in conjunction with codeine
in prescription cough syrup
. The syrup by itself contains 7% alcohol. The traditional mixture of Sprite and cough syrup with codeine, which is known as "purple drank
" or "Sizzurp", is popularized in the rap world, especially in the Houston
area. It is also sometimes used to counteract nausea caused by illicit opioid use.
- Promethazine. U.S. National Library of Medicine and National Institutes of Health. .