Adult: As promethazine hydrochloride: 25 mg at night, may be increased up to 25 mg bid if necessary. Alternatively, 10-20 mg 2-3 times daily. Child: As promethazine hydrochloride: 2-5 years As solution or syr: 5-15 mg daily in 1 or 2 divided doses; >5-10 years As tab/solution or syr: 10-25 mg daily in 1 or 2 divided doses; >10 years As tab/solution or syr: Same as adult dose.
Oral Insomnia
Adult: For short-term management: As promethazine hydrochloride: 20-50 mg at night. Alternatively, 25 mg or 50 mg as a single night-time dose. Child: As promethazine hydrochloride: 2-5 years As solution or syr: 15-20 mg; >5-10 years As tab/solution or syr: 20-25 mg; >10 years As tab: Same as adult dose. All doses are given as a single night-time dose.
Oral Nausea and vomiting
Adult: As promethazine hydrochloride: 12.5-25 mg every 4-6 hours, as needed. Due to labyrinthitis and other causes: As promethazine teoclate: 25 mg at night, may be increased to 50 or 75 mg at night, or to 25 mg 2 or 3 times daily if necessary. Max: 100 mg daily. Child: Due to labyrinthitis and other causes: As promethazine teoclate: 5-10 years 12.5-37.5 mg daily. >10 years Same as the lower adult dose.
Oral Motion sickness
Adult: As promethazine hydrochloride: Prophylaxis: 20 mg or 25 mg at night before travelling, may be repeated after 6-8 hours if necessary. Alternatively, 25 mg given 30-60 minutes before travelling, may be repeated 8-12 hours later as needed. As promethazine teoclate: Prophylaxis: 25 mg given at bedtime on the night before travel or 1-2 hours before travelling. Treatment: 25 mg as soon as possible and repeated in the same evening, followed by a 3rd dose the next evening. Child: As promethazine hydrochloride: 2-5 years As solution or syr: 5 mg; >5-10 years As tab/solution or syr: 10 mg; >10 years As tab/solution or syr: Same as adult dose. All doses are given the night before the journey and repeated after 6-8 hours if necessary.
Parenteral Sedation
Adult: As promethazine hydrochloride: 25-50 mg via deep IM inj or slow IV inj (diluted) or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute. Max: 100 mg. Child: As promethazine hydrochloride: 5-10 years 6.25-12.5 mg via deep IM inj.
Parenteral Nausea and vomiting
Adult: As promethazine hydrochloride: 12.5-25 mg via deep IM inj or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute, repeated at intervals of not less than 4 hours. Max: 100 mg daily.
Parenteral Obstetric analgesia
Adult: Adjunct: As promethazine hydrochloride: Early labour: 50 mg. Established labour: 25-75 mg in combination with analgesics, may be repeated once or twice at 4-hour intervals. Max 100 mg daily while in labour. Doses are given via deep IM inj or slow IV inj (diluted) or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute.
Parenteral Adjunct to pre- or post-operative sedation
Adult: In combination with analgesics or hypnotics (at reduced dose): As promethazine hydrochloride: 25-50 mg via deep IM inj or slow IV inj (diluted) or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute. Child: As promethazine hydrochloride: >2 years In combination with analgesics or hypnotics (at reduced dose): 1.1 mg/kg via deep IM inj or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute. Max: 12.5-25 mg. Use the lowest effective dose.
Parenteral Allergic conditions
Adult: As promethazine hydrochloride: 25-50 mg via deep IM inj or slow IV inj (diluted). Max: 100 mg. Alternatively, 25 mg via deep IM inj or IV infusion in a Max concentration of 25 mg/mL and at a Max rate of 25 mg/minute, may be repeated in 2 hours if necessary. Switch to oral route as soon as possible. Child: As promethazine hydrochloride: 5-10 years 6.25-12.5 mg via deep IM inj.
Rectal Nausea and vomiting
Adult: As promethazine hydrochloride supp: 12.5-25 mg every 4-6 hours, as needed.
Rectal Allergic conditions
Adult: As promethazine hydrochloride supp: 25 mg at bedtime, or 12.5 mg before meals and at bedtime if necessary. Usual range: 6.25-12.5 mg tid. Dosage must be adjusted to the lowest effective dose to relieve symptoms.
Rectal Sedation
Adult: As promethazine hydrochloride supp: 25-50 mg for night-time, pre-surgical or obstetric sedation.
Rectal Motion sickness
Adult: As promethazine hydrochloride supp: Initially, 25 mg 30-60 minutes before travelling, may be repeated 8-12 hours later as needed. Maintenance: 25 mg bid.
Administration
May be taken with or without food.
Reconstitution
Slow IV inj: Dilute the 2.5% solution to 10 times its volume with water for inj immediately prior to use.
Incompatibility
Promethazine hydrochloride: Incompatible with alkaline substances, aminophylline, barbiturates, benzylpenicillin salts, chloramphenicol Na succinate, chlorothiazide Na, cefotetan disodium, dimenhydrinate, furosemide, heparin Na, hydrocortisone Na succinate, methicillin Na, morphine sulfate, and nalbuphine hydrochloride.
Contraindications
Coma, compromised respiratory function, at risk for respiratory failure (e.g. COPD, sleep apnoea), lower respiratory tract symptoms, including asthma, bronchiectasis, bronchitis; CNS depression of any cause. Children <2 years; children with symptoms suggestive of Reye’s syndrome or hepatic disease. SC and intra-arterial administration. Concurrent use with or within 14 days of stopping MAOI.
Special Precautions
Patient with bone marrow depression; cerebrovascular disease, CV disease (e.g. severe coronary artery disease), narrow-angle glaucoma, hypovolaemia, decreased gastrointestinal motility, xerostomia, visual problems, bladder neck obstruction, pyloroduodenal obstruction, stenosing peptic ulcer, prostatic hypertrophy, urinary retention, Reye’s syndrome, myasthenia gravis, Parkinson’s disease; epilepsy, history of seizures, head trauma, brain damage, alcoholism. Patient subjected to heat exposure, strenuous exercise, dehydration. Avoid extravasation (IV inj). Renal and hepatic impairment. Children ≥2 years. Pregnancy and lactation.
Adverse Reactions
Significant: Anticholinergic effects (e.g. blurred vision, xerostomia, constipation, urinary retention), CNS depression, extrapyramidal symptoms, including akathisia, tardive dyskinesia, pseudoparkinsonism and acute dystonic reactions; orthostatic hypotension, leucopenia and agranulocytosis, cholestatic jaundice, photosensitivity, impaired core body temperature regulation; lowered seizure threshold. Blood and lymphatic system disorders: Thrombocytopenia. Rarely, haemolytic anaemia. Cardiac disorders: Palpitation, bradycardia, tachycardia. Gastrointestinal disorders: Gastric irritation, nausea, vomiting. General disorders and administration site conditions: Tiredness; inj site reactions (e.g. burning sensation, pain, erythema, swelling, phlebitis). Hepatobiliary disorders: Rarely, jaundice. Immune system disorders: Rarely, anaphylaxis. Metabolism and nutrition disorders: Anorexia. Musculoskeletal and connective tissue disorders: Muscle spasms, tic-like movements of head and face. Nervous system disorders: Dizziness, headache, restlessness, incoordination, paradoxical hyperexcitability (in children). Psychiatric disorders: Drowsiness, disorientation, confusion, nightmares, hallucination. Respiratory, thoracic and mediastinal disorders: Asthma, nasal congestion. Skin and subcutaneous tissue disorders: Urticaria, rash, pruritus, dermatitis. Vascular disorders: Hypotension. Potentially Fatal: Arrhythmias, respiratory depression (in children), apnoea, neuroleptic malignant syndrome (NMS); severe tissue injury, including gangrene (inj).
This drug may cause marked drowsiness, dizziness, disorientation, or confusion; if affected, do not drive or operate machinery. Avoid prolonged exposure to sunlight.
Monitoring Parameters
Monitor mental status and CNS effects; signs and symptoms of tissue injury with IV administration.
Overdosage
Symptoms: Children: Excitation, incoordination, ataxia, athetosis, hallucinations. Adult: Drowsiness, profound hypotension, coma. Convulsions which may be preceded by coma or excitement, may occur in both adults and children. Management: Symptomatic and supportive treatment. Induce vomiting with ipecacuanha or perform gastric lavage. Maintain adequate respiratory and circulatory status. Convulsions may be treated with diazepam or other suitable anticonvulsants. Administer IV fluids and repositioning for hypotension; may consider use of norepinephrine or phenylephrine for severe hypotension unresponsive to IV fluids and repositioning.
Drug Interactions
May enhance the action of any anticholinergic agent, TCA, sedative or hypnotic. May increase and prolong the sedative effects of other CNS depressants such as barbiturates, general anaesthetics, narcotic analgesics, tranquilisers. May mask the warning signs of ototoxicity caused by salicylates. May cause lowered seizure threshold with narcotics and local anaesthetics. May reverse the vasopressor effects of epinephrine. Potentially Fatal: Increased risk of extrapyramidal effects with MAOIs.
Food Interaction
May enhance the CNS depressant effects of alcohol.
Lab Interference
May produce false-positive or false-negative results with immunological urine pregnancy tests (hCG-based). May cause false-positive results with urine detection of amphetamine or methamphetamine; increased serum glucose during glucose tolerance tests. May inhibit the cutaneous histamine response thus producing false-negative results during allergen testing. May interfere with blood grouping in the ABO system.
Action
Description: Mechanism of Action: Promethazine is a phenothiazine derivative with antihistamine, sedative, antiemetic, anti-motion sickness, and anticholinergic properties. It blocks the postsynaptic mesolimbic dopaminergic receptors in the brain; exhibits a strong α-adrenergic blocking activity and depresses the release of hypothalamic and hypophyseal hormones. Promethazine also competitively antagonises the effects of histamine at the H1-receptor sites on effector cells, reduces the stimuli to brainstem reticular system, and causes an antiemetic activity may be due to its muscarinic blocking effects. Onset: Oral, IM: Approx 20 minutes; IV: Approx 5 minutes. Duration: 4-6 hours (up to 12 hours). Pharmacokinetics: Absorption: Well absorbed from the gastrointestinal tract and after IM inj. Bioavailability: Approx 25% (oral); 21.7-23.4% (rectal). Time to peak plasma concentration: 2.8 ± 1.4 hours (oral syr); 8.2 ± 3.4 hours (rectal). Distribution: Widely distributed in the body. Crosses the blood-brain barrier and placenta; enters breast milk (small amounts). Volume of distribution: 13.4 ± 3.6 L/kg. Plasma protein binding: 76-93%. Metabolism: Extensively metabolised in the liver via hydroxylation by CYP2D6 and N-demethylation by CYP2B6 to promethazine sulfoxide and N-desmethylpromethazine; undergoes significant first-pass effect. Excretion: Via urine and faeces (as inactive metabolites). Elimination half-life: Oral syr, supp: 16-19 (range: 4-34) hours; IV: 9-16 hours; IM: approx 10 hours.
Chemical Structure
Promethazine Source: National Center for Biotechnology Information. PubChem Database. Promethazine, CID=4927, https://pubchem.ncbi.nlm.nih.gov/compound/Promethazine (accessed on Jan. 21, 2020)
Storage
Oral solution or syr/tab/inj: Store between 15-30°C. Protect from light. Supp: Store between 2-8°C.
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