General Remarks and Pharmacology
Promethazine (sold as Phenergan and Promethegan) is a first-generation H1 receptor antagonist (antihistamine) and anti-nausea medication available by prescription in the United States, and over-the-counter in the United Kingdom, Switzerland, Australia, South Africa, New Zealand and many other countries. Promethazine belongs to the phenothiazine class of drugs. It can be prescribed by itself or in combination with other drugs, such as codeine.
Promethazine has strong anti-cholinergic and sedative as well as strong antiallergic and antiemetic effects. Previously in its history, promethazine has also been used as an anti-psychotic, although it is generally not administered for this purpose (promethazine has only approximately 1/10 of the antipsychotic strength of chlorpromazine).
Promethazine is well and rapidly absorbed after oral dosing, but undergoes considerable first-pass-metabolisation leading to a variable bioavailability. Onset of action is often noted 20 minutes after oral administration. One single dose acts for 2 to 8 hours in a dose depending manner. Bioavailability after i.m.-injection is higher and onset of action even faster compared to oral administration.
For preoperative sedation and to counteract postnarcotic nausea
As antiallergic medication to combat hayfever, allergic rhinitis etc. To treat allergic reactions it can be given alone or in combination with oral decongestans like (pseudo-)ephedrine.
Sometime used to alleviate the symptoms of alcohol and drug withdrawal
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.
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
Severly impared liver function
Urine hesitancy due to enlargement of the prostate gland
Promethazine is generally well tolerated. Typical side-effects are:
Drowsiness, Dizziness, Fatigue, more rarely vertigo
Confusion in the elderly
Sometimes Hypotension and Tachycardia
Allergic Skin Reactions, photosensitivity (much lower frequency compared to chlorpromazine)
Extrapyramidal Reactions possible after longterm treatment, but infrequent. Development of Tardive Dyskinesia has also been noted during longterm treatment
Single cases of Leukopenia and Agranulocytosis (dangerous fall of white blood cells)
Respiratory depression in patients under age of two and in those with severly compromised pulmonal function
Extremely rare are seizures
Also extremely rare but most serious malignant neuroleptic syndrome
Elderly patients may be more sensitive to anticholinergic properties of the drug.
Rare cases of other serious side effects have been seen.
Promethazine itself is devoid of any addictive properties and can be used safely in patients with a history of drug abuse or dependence.
Promethazine may intensify the action of other centrally acting drugs. Decrease the dose of other drugs as needed.
Depending on disease and clinical condition (age, liver function):
Mild to moderate cases of Agitation : 25mg to 50mg oral 3 to 4 times daily
Insomnia : Depending upon severity 25 to 100mg oral at bedtime
Alcohol and drug withdrawal : Depending upon severity of symptoms from 25mg 4 times up to 100mg 3 times daily.
Pre- and postoperative treatment : 25mg oral or i.m., repeat as needed
Allergy : 25mg oral 3 to 4 times daily, sometimes extra 25mg are given at bedtime
In pediatric patients doses as low as 5 to 10mg 3 times daily may suffice. For precise dosing syrup forms exist.
All patients should have measured their blood pressure frequently. During longterm 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.
Other useful drug information: Metronidazole | Neurontin | Darvocet | Calcium | Lovastatin | Etodolac | Clonazepam
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