Brands, Medical Use, Clinical Data
- Anti-allergic Agents
- Phenothiazine Derivatives
- Opthalmic drops
Brands / Synonyms
Allergan; Aprobit; Atosil; Avomine; Dimapp; Diphergan; Diprazine; Diprozin; Dorme; Duplamin; Fargan; Fellozine; Fenazil; Fenergan; Fenetazina; Genphen; Hiberna; Histargan; Iergigan; Isophenergan; Isopromethazine; Lercigan; Lergigan; Lilly 1516; Mymethazine Fortis; Phargan; Phenargan; Phencen; Phenergan; Phenergan Fortis; Phensedyl; Pilpophen; Pipolphen; Proazaimine; Proazamine; Procit; Promazinamide; Prometasin; Prometazin; Prometh Fortis; Prometh Plain; Promethacon; Promethaine; Promethazin; Promethazine; Promethazine and Phenylephrine; Promethazine and Codeine; Promethazine and Dextromethorphan; Promethazine DM; Promethazine Hcl; Promethazine Plain; Promethazine VC; Promethazine, Phenylephrine and Codeine; Promethegan; Promethiazine; Promezathine; Prorex; Protazine; Prothazin; Prothazine; Provigan; Pyrethia; Pyrethiazine; Remsed; Romergan; Synalgos; Tanidil; Thiergan; Valergine; Vallergine; Zipan-25
For the treatment of allergic disorders, itching, nausea and vomiting.
Promethazine, a phenothiazine, is an H1-antagonist with anticholinergic, sedative, and antiemetic effects and some local anesthetic properties. Promethazine is used as an antiemetic or to prevent motion sickness.
Mechanism of Action
Like other H1-antagonists, promethazine competes with free histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. The relief of nausea appears to be related to central anticholinergic actions and may implicate activity on the medullary chemoreceptor trigger zone.
On average, 88% of a promethazine dose is absorbed after oral administration; however, the absolute bioavailability is only 25% because of first-pass clearance.
Symptoms of overdose include mild depression of the central nervous system and cardiovascular system to profound hypotension, respiratory depression, unconsciousness, and sudden death. Other reported reactions include hyperreflexia, hypertonia, ataxia, athetosis, and extensor-plantar reflexes (Babinski reflex). LD50=55mg/kg (I.V. in mice)
Biotrnasformation / Drug Metabolism
Injection: Promethazine is contraindicated in comatose states, in patients who have received large
amounts of central-nervous-system depressants (alcohol, sedative hypnotics, including barbiturates, general
anesthetics, narcotics, narcotic analgesics, tranquilizers, etc.), and in patients who have demonstrated an
idiosyncrasy or hypersensitivity to promethazine.
Under no circumstances should promethazine be given by intra-arterial injection due to the likelihood of severe
arteriospasm and the possibility of resultant gangrene
Promethazine HCl injection should not be given by the subcutaneous route; evidence of chemical irritation has been
noted, and necrotic lesions have resulted on rare occasions following subcutaneous injection. The preferred
parenteral route of administration is by deep intramuscular injection.
Syrup, Tablets and Suppositories: Phenergan Tablets and Suppositories are contraindicated for use in
pediatric patients less than two years of age.
Phenergan Tablets and Suppositories are contraindicated in comatose states, and in individuals known to be
hypersensitive or to have had an idiosyncratic reaction to promethazine or to other phenothiazines.
Antihistamines are contraindicated for use in the treatment of lower respiratory tract symptoms including
Narcotics And Barbiturates: The CNS-depressant effects of narcotics are additive with promethazine
Monoamine Oxidase Inhibitors (Maoi): Drug interactions, including an increased incidence of
extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly. Although such a
reaction has not been reported with promethazine, the possibility should be considered.
Syrup, Tablets and Suppositories:
CNS Depressants - Phenergan Tablets and Suppositories may increase, prolong, or
intensify the sedative action of other central-nervous-system depressants, such as alcohol, sedatives/hypnotics
(including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and
tranquilizers; therefore, such agents should be avoided or administered in reduced dosage to patients receiving
promethazine HCl. When given concomitantly with Phenergan Tablets and Suppositories, the dose of barbiturates should
be reduced by at least one-half, and the dose of narcotics should be reduced by one-quarter to one-half. Dosage must
be individualized. Excessive amounts of promethazine HCl relative to a narcotic may lead to restlessness and motor
hyperactivity in the patient with pain; these symptoms usually disappear with adequate control of the pain.
Epinephrine - Because of the potential for Phenergan to reverse epinephrineís
vasopressor effect, epinephrine should NOT be used to treat hypotension associated with Phenergan Tablets and
Anticholinergics - Concomitant use of other agents with anticholinergic properties
should be undertaken with caution.
Monoamine Oxidase Inhibitors (MAOI) - Drug interactions, including an increased
incidence of extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly.
This possibility should be considered with Phenergan Tablets and Suppositories.