promethazine

Promethazine
Systematic (IUPAC) name
N, N-dimethyl-1-(10H-phenothiazin-10-yl)propan-2-amine
Identifiers
CAS number	60-87-7
ATC code	D04AA10 R06AD02, R06AD05
PubChem	4927
DrugBank	APRD00601
Chemical data
Formula	C17H20N2S
Mol. mass	284.425 g/mol
Pharmacokinetic data
Bioavailability	88% absorbed but after first-pass metabolism reduced to 25% absolute bioavailability
Protein binding	93%
Metabolism	Hepatic glucuronidation and sulfoxidation
Half life	16-19 hours
Excretion	Renal and biliary
Therapeutic considerations
Pregnancy cat.	C(AU) C(US)
Legal status	P(UK) ℞-only(US) (injection POM(UK))
Routes	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®, Prothiazine®).

Promethazine also has strong anticholinergic and sedative/hypnotic 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

• 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
• As a motion sickness or seasickness remedy when used with Ephedrine or Pseudoephedrine.
• As an antipruritic (pruritus vulvae).
• To combat moderate to severe morning sickness and hyperemesis gravidarum.

Contraindications

• 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

Typical side effects are:

• 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
• Constipation

Dosage

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

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

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, which is known as "purple drank", is popularized in the rap world, especially in the Houston area.^[1]Noted rapper Dwayne ( Lil' Wayne) Carter has been known to use promethazine in a recreational manner. He can often be heard bragging about his heavy abuse of the controlled substance.

External links

• Letter from Wyeth Pharmaceuticals to practitioners regarding use of Phenergan in under twos. (PDF format)

• U.S. National Library of Medicine and National Institutes of Health information on promethazine.

References

• Basic and Clinical Pharmacology, 9th ed (2004). Katzung, Bertram G. pp. 264–265.

Donate to Wikimedia