From Self-sufficiency
Jump to: navigation, search
Systematic (IUPAC) name
Clinical data
  • AU: C
  • US: C (Risk not ruled out)
Routes of
Oral, rectal, IV, IM, topical
Legal status
Legal status
Pharmacokinetic data
Bioavailability 88% absorbed but after first-pass metabolism reduced to 25% absolute bioavailability
Protein binding 93%
Metabolism Hepatic glucuronidation and sulfoxidation
Biological half-life 16-19 hours
Excretion Renal and biliary
CAS Number 60-87-7
58-33-3 (hydrochloride)
ATC code D04AA10 (WHO) R06AD02, R06AD05
PubChem CID 4927
DrugBank APRD00601
ChemSpider 4758
Chemical data
Formula C17H20N2S
Molar mass 284.42 g/mol[[Script error: No such module "String".]]
Script error: No such module "collapsible list".
Script error: No such module "TemplatePar".Expression error: Unexpected < operator.

Promethazine is a first-generation H1 receptor antagonist of the phenothiazine chemical class used medically as an antihistamine antiemetic. It has a strong sedative effect and in some countries is prescribed for insomnia when benzodiazepines are contraindicated. It is available over the counter in the United Kingdom, Australia, Canada, Switzerland, and many other countries, but by prescription in the United States (brand names Phenergan, Promethegan, Romergan, Fargan, Farganesse, Prothiazine, Avomine, Atosil, Receptozine, Lergigan).[1]


Chemically, promethazine hydrochloride appears as a white to faint yellow crystlline powder that is practically odorless. Slow oxidation may occur upon prolonged exposure to air usually causing blue discoloration. Promethazine as the hydrochloride salt is freely soluble in water and somewhat soluble in alcohol. Promethazine is a chiral compound, occurring as a mixture of enantiomers (pictured).[2]


Mechanism of action

  • Promethazine is a phenothiazine derivative that competitively blocks histamine H1 receptors without blocking the secretion of histamine. It also is a very weak dopamine antagonist.[6]
  • It has sedative, anti-motion-sickness, anti-emetic, and anti-cholinergic effects.[citation needed]

Side effects

Some common side effects include:

  • Confusion in the elderly
  • Drowsiness, dizziness, fatigue, more rarely vertigo
  • Dry mouth
  • Respiratory depression in patients under age of 2 and in those with severely compromised pulmonal function
  • Constipation
  • Chest Discomfort/Pressure. (typically in cases when patient is already taking medication for high blood pressure)
  • Euphoria (very rare, except with high IV doses and/or coadministration with opioids/CNS depressants)
  • Restless legs [7]
  • Paresthesia
  • Short temper/Irritability

Extremely rare side effects include:

IV administration: Dilute with 0.9% NaCl or D5W. CONCENTRATION: Doses should not exceed a concentration of 25mg/ml. Administer through a large-bore vein through a running IV line into the most distal port. Slight yellow color does not alter potency. Do not administer if precipitate is present. RATE: Administer each 25mg slowly, over at least 10-15min. Rapid administration may produce a transient fall in blood pressure. [8] Serious complications including those listed above have resulted from improper parenteral administration, including those requiring surgical intervention and amputation.

Because of potential for more severe side effects, this drug is on the list to avoid in the elderly. (See NCQA’s HEDIS Measure: Use of High Risk Medications in the Elderly).

Laboratory examinations

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.[citation needed]

Product liability lawsuit

In 2009, the U.S. Supreme Court ruled on a product liability case involving promethazine. Diana Levine, a woman suffering from a migraine, was administered Wyeth's Phenergan via IV push. The drug was injected improperly resulting in gangrene and subsequent amputation of her right forearm below the elbow. A state jury awarded her $6 million in punitive damages.

The case was appealed to the Supreme Court on grounds of federal preemption and substantive due process.[9] The Supreme Court upheld the lower courts' rulings stating that "Wyeth could have unilaterally added a stronger warning about IV-push administration" without acting in opposition to federal law.[10] In effect, this means that drug manufacturers can be held liable for injuries if warnings of potential adverse effects (approved by the U.S. Food and Drug Administration, "FDA") are deemed insufficient by state courts.

On September 9, 2009, the FDA made the decision that a black box warning for injection be put on promethazine stating the contraindication for subcutaneous administration. The preferred administrative route is intramuscular (IM) which reduces risk of surrounding muscle and tissue damage [11]


Cite error: Invalid <references> tag; parameter "group" is allowed only.

Use <references />, or <references group="..." />

External links

  • "Promethazine". U.S. National Library of Medicine and National Institutes of Health. 

fr:Prométhazine it:Prometazina ka:პიპოლფენი hu:Prometazin nl:Promethazine ja:プロメタジン nn:Prometazin pl:Prometazyna pt:Prometazina ru:Прометазин fi:Prometatsiini sv:Prometazin th:โปรเมทาซีน

  1. RxList: Promethazine
  2. RxList: Promethazine Description
  3. 3.0 3.1 3.2 3.3 3.4 RxList Indications for Promethazine
  4. Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  5. [1]
  6. David J. McCann and Brett Roth, Toxicity, Antihistamine, eMedicine Toxicology, updated June 21, 2007
  7. Cordingley Neurology
  8. Davis Drug Guide for Nurses Eleventh Edition pgs. 1017-1020
  9. Liptak, Adam (2008-09-18). "Drug Label, Maimed Patient and Crucial Test for Justices". The New York Times. Retrieved 2008-10-31. 
  10. Stout, David (2009-03-04). "Drug Approval Is Not a Shield From Lawsuits, Justices Rule". The New York Times. Retrieved 2009-03-04.