Because the chemical structure of promethazine is different from that of other antipsychotic agents of the phenothiazine group, it has a weaker antipsychotic effect. In therapeutic doses it has no effect on the cardiovascular system. Clinical effects occur 20 min after oral administration (15-60 min on average), 2 min after I/M administration or 3-5 min after I/V administration and usually last for 4-6 h (sometimes lasting up to 12 h). Intensively metabolized in the liver on “first pass” mainly by S-oxidation. Promethazine sulfoxides and N-demethyl-promethazine are the main metabolites that are determined in the urine. The T1/2 of promethazine is 7-15 h. It is excreted mainly by the kidneys; to a lesser extent by the intestine.
Indications for use of Prometazine
- Allergic diseases (including urticaria, serum sickness, hay fever, allergic rhinitis, allergic conjunctivitis, angioedema, pruritus);
- adjuvant therapy of anaphylactic reactions (after the acute manifestations are stopped by other means, for example, epinephrine /adrenaline/);
- As a sedative in the pre- and postoperative period;
- to prevent or relieve nausea and vomiting associated with anesthesia and/or occurring in the postoperative period;
- Postoperative pain (in combination with analgesics);
- kinetosis (to prevent and relieve dizziness and nausea during transportation);
- as a component of lytic mixtures used to potentiate anesthesia in surgical practice (for parenteral use).
It is administered orally, intramuscularly and intravenously.
Maximal daily dose for adults is 150 mg.
Intramuscularly – adults 25 mg once a day, if necessary 12.5-25 mg every 4-6 hours.
In treatment of allergic diseases Prometazine is prescribed orally in a dose of 25 mg once a day in the evening or 25 mg twice a day (morning and evening). The drug should be prescribed in the minimum effective dose.
For prevention and treatment of nausea and vomiting the drug is prescribed orally or intramuscularly in a single dose of 25 mg. If necessary, 25 mg may be administered every 4-6 hours. As a sedative in surgery on the eve of surgery, it is prescribed orally or intramuscularly in a dose of 25-50 mg once at night. For preoperative preparation 2.5 hours before surgery 50 mg Prometazine is administered as part of lytic mixtures, if necessary in 1 hour the administration can be repeated.
For induction of anesthesia and analgesia in certain diagnostic and surgical interventions such as repeated bronchoscopy, ophthalmic surgery, Prometazine may be administered v/v in doses of 0.15-0.3 mg/kg body weight.
In children over 2 months old the drug can be administered 3 to 5 times per day in a dose of 0.5 to 1 mg/kg of body weight. In severe cases the single dose for intravenous injection may be increased to 1-2 mg/kg of body weight.
Children aged 6 to 14 years are prescribed orally in dose of 25 mg (1 tablet) 3 to 4 times daily. It is not recommended to divide the tablet tablet in half; therefore, this dosage form is not indicated for children under 6 years of age.