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CAS No. 58-33-3
C17H20N2S·HCL
M. wt 320.9
DBL® Promethazine Hydrochloride Injection B.P. is a clear, colourless solution of pH 5.0-6.0. Each mL of the solution contains 25.0mg promethazine hydrochloride, 0.10mg disodium edetate, 1.30 microlitre glacial acetic acid, 27.2mg sodium acetate and 1.32mg sodium metabisulfite in water for injections.
Promethazine is a phenothiazine derivative with potent antihistaminic and sedative-hypnotic effects. It also has antiemetic, antivertigo, anti-motion sickness, anticholinergic effects and local anaesthetic actions.
Antihistamines competitively and reversibly antagonise the effects of histamine at the H1-receptor sites on effector cells which are responsible for vasodilatation, increased capillary permeability, flare and itch reactions in the skin, and to some extent for contraction of smooth muscle in the bronchi and gastrointestinal tract.
The precise mechanism of the CNS effects of promethazine is unknown. The sedative effects may involve antagonism at central histamine, serotonin and acetylcholine receptors, or central alpha-adrenergic stimulation. However, paradoxical CNS stimulation may occur, especially in children, and at high doses may be attributable to antimuscarinic activity. The antiemetic, anti-motion sickness and antivertigo effects of promethazine are possibly a result of central anticholinergic actions on the vestibular apparatus and the integrative vomiting centre and medullary chemoreceptive trigger zone of the midbrain.
The anticholinergic (antimuscarinic) actions of promethazine provide a drying effect on the oral and nasal mucosa.
Promethazine is well absorbed following intramuscular and intravenous injection and the onset of antihistaminic properties occurs about 20 minutes after intramuscular injection and 3 to 5 minutes after intravenous injection. It has a prolonged antihistamine action, which may persist for 12 hours or more. The duration of sedative effects may range from 2-8 hours depending on the dose and route of administration.
Promethazine is widely distributed within body tissues. Promethazine crosses the blood/brain barrier and the placenta and is excreted in breast milk. It is metabolised by the liver and excreted slowly in the urine and faeces mainly as inactive promethazine sulphoxide and glucuronides; elimination half lives of 7 to 14 hours have been reported.
DBL® Promethazine Hydrochloride Injection BP is indicated for the following conditions:
Treatment of allergic reactions such as:
uncomplicated allergic conditions of the immediate type, eg. Pruritus, urticaria
and angioedema, when oral therapy is impossible or contraindicated;
Treatment and prevention of vomiting including:
motion sickness;
drug induced nausea;
prevention and control of nausea and vomiting associated with certain types of
anaesthesia and surgery, such as procedures with a high incidence of
postoperative vomiting (eg. gynaecological surgery, strabismus or middle ear
surgery, and electroconvulsive therapy); in patients with a past history of
motion sickness or post operative vomiting; and in patients in whom avoidance of
vomiting is crucial (eg. Neurosurgery and eye surgery);
Promethazine has sedative effects and it is also used in:
preoperative, postoperative and obstetric (during labour) sedation.
Promethazine is contraindicated for use in pediatric patients less than two years of age.
Promethazine is contraindicated in patients who have exhibited hypersensitivity to the drug or other phenothiazine derivatives.
Promethazine is also contra-indicated in the following patients:
comatose
after administration of large doses of other CNS depressants (eg. alcohol
general anaesthetics, opioid analgesics, tranquillisers, etc.)
DBL® Promethazine Hydrochloride injection BP must not be administered intra-arterially due to the likelihood of severe arteriospasm and the possibility of resultant gangrene. DBL® Promethazine Hydrochloride injection BP should not be given subcutaneously, as the solution is irritant and may produce necrotic lesions.
Promethazine should not be used in pediatric patients less than two years of age because of the potential for fatal respiratory depression. Post marketing cases of respiratory depression including fatalities have been reported with the use of Promethazine in pediatric patients less than two years of age. A wide range of weight-based doses of promethazine have resulted in respiratory depression in these patients.
Caution should be excerised when administering Promethazine to pediatric patients two years of age or older, because the potential for fatal respiratory depression and apnea are strongly associated with Prometahzine products and are not directly related to individualized weight-based dosing, which might otherwise permit safe administration. It is recommended that the lowest effective dose of Promethazine be used in Pediatric patients and concomitant adminsitartion of other drugs with respiratory depressant effects be avoided.
Use of promethazine should be avoided in acutely ill or dehydrated children, since these patients have an increased susceptibility to dystonias. Use of the drug should also be avoided in children and adolescents with signs and symptoms which suggest Reye's syndrome, since the potential extrapyramidal effects produced by the drug may obscure the diagnosis of, or be confused with the CNS signs and symptoms of this condition or other hepatic diseases. Excessively large doses in children may cause hallucinations, convulsions and sudden death.
Antiemetics are not recommended for treatment of uncomplicated vomiting in pediatric patients, and their use should be limited to prolonged vomiting of known etiology.
As a result of its anticholinergic actions, promethazine should be used with caution in patients with narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstruction, and bladder-neck obstruction. It should also be used with caution in patients with bone-marrow depression, jaundice, impaired liver function, epilepsy, asthmatic attack, or cardiovascular disorders.
Promethazine may mask the adverse effects of ototoxic medications; eg. tinnitus, dizziness. Concurrent use of promethazine and other hypotension-producing medications may produce additive hypotensive effects. Concurrent use of promethazine with other hepatotoxic medications may increase the potential for hepatotoxicity, and patients should be carefully monitored.
Promethazine's anti-emetic action may mask the symptoms of acute appendicitis or overdose of other drugs.
QT interval prolongation has been reported with phenothiazines.
Promethazine may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving a vehicle or operating machinery. The concomitant administration of alcohol, sedative-hypnotics, general anaesthetics, opioids, tranquillisers or other CNS depressants may have an additive sedative effect. Patients should be warned accordingly.
DBL® Promethazine Hydrochloride Injection BP contains sodium metabisulfite, which may cause allergic-type reactions, including anaphylactic symptoms and life-threatening or less severe asthmatic episodes, in certain susceptible people.
Category C. When given in high doses during late pregnancy, phenothiazines have cause prolonged extrapyramidal disturbances in the child.
The exact amount of promethazine excreted into breast milk is unknown, but amounts are usually small. Promethazine should be used with caution in nursing women. The infant should be observed for side effects, especially sedation.
Anticholinergic effects may be potentiated when these medications are used concurrently with promethazine. Patients should be advised to report occurrence of gastrointestinal problems promptly, since paralytic ileus may occur with concurrent therapy.
As promethazine may lower the convulsion threshold, dosage adjustment of anticonvulsant medication may be required.
Concurrent use of promethazine with beta-blockers, especially propranolol, may result in increased plasma concentrations of each agent because of inhibition of metabolism. This may result in additive hypotensive effects, irreversible retinopathy, cardiac arrhythmias and tardive dyskinesia.
The neuronal uptake of guanethidine may be inhibited when used with promethazine, causing a decrease in the antihypertensive effect.
Increase serum prolactin concentrations, thereby interfering with the effects of bromocriptine. Dosage adjustments of bromocriptine may be necessary.
Promethazine may potentiate the sedative action of other CNS depressants such as barbiturates, antihistamines, tranquillisers, opioids, general anaesthetics, or alcohol.
The antiparkinsonian effects of levodopa may be inhibited when used concurrently with promethazine because of blockade of dopamine receptors in the brain.
Concurrent use of intrathecal metrizamide with promethazine may lower the seizure threshold. Promethazine should be discontinued at least 48 hours before, and not resumed for at least 24 hours following myelography.
Concurrent use of MAO inhibitors with promethazine may prolong and intensify the anticholinergic and CNS depressant effects, and may increase the risk of hypotension and extrapyramidal reactions.
Concurrent use of other phenothiazine derivatives may increase the severity and frequency of extrapyramidal effects.
Concurrent use of promethazine with quinidine may result in additive cardiac effect.
The alpha-adrenoceptor agonist effects of adrenaline may be blocked when it is used concurrently with promethazine, possibly resulting in severe hypotension and tachycardia. The alpha-adrenoceptor blocking activity of promethazine may also decrease the pressor response to ephedrine, metaraminol and methoxamine; decrease the stimulant effects of amphetamines; and antagonise the anorectic effect of the centrally acting appetite suppressants.
Concurrent use of tricyclic antidepressants may intensify the anticholinergic effects and increase the risk of hypotension and extrapyramidal effects.
Solutions of promethazine hydrochloride are incompatible with alkaline substances, which precipitate the insoluble promethazine base. Promethazine has been reported to be incompatible with solutions containing the following compounds: aminophylline, benzylpenicillin salts, cefepime hydrochloride, cefotetan disodium, cephazolin, chloramphenicol sodium succinate, chloroquine phosphate, chlorothiazide sodium, dexamethasone sodium phosphate, dextran, dimenhydrinate, flocloxacillin sodium, foscarnet, frusemide, heparin sodium, hydrocortisone sodium succinate, ketorolac tromethamine, meglumine diatrizoate, meglumine iodipamide, methicillin sodium, methohexitone sodium, methotrexate sodium, morphine sulfate, nalbuphine hydrochloride (some formulations only), nitrofurantoin, penicillin G, pentobarbitone sodium, phenobarbitone sodium, phenytoin sodium, piperacillin, sodium bicarbonate, sodium diatizoate, sodium iothalamate, sulphafurazole, thiopentone sodium.
Promethazine may interfere with diagnostic pregnancy tests based on immunological reactions between HCG and anti-HCG, and may cause an increase in glucose tolerance. Promethazine may produce false negative results in skin tests using allergen extracts. It is recommended that antihistamines are discontinued at least 72 hours before testing begins.
CNS: Sedation is the most prominent CNS effect promethazine. Extrapyramidal reactions may occur with high doses and usually subside with dosage reduction. Other reported reactions include dizziness, lassitude, tinnitus, confusion, disorientation, incoordination, fatigue, blurred vision, euphoria, diplopia, nervousness, irritability, tremors, convulsions, oculogyric crises, excitation, catatonic-like states, and hysteria.
Cardiovascular: Tachycardia, bradycardia, faintness, dizziness, transient minor increases in blood pressure, and hypotension have been reported following the use of promethazine hydrochloride injection. Venous thrombosis at the injection site has been reported.
Gastrointestinal: Nausea and vomiting have been reported, usually in association with surgical procedures and combination drug therapy. Loss of appetite, epigastric distress, constipation and diarrhoea have also been reported.
Allergic: Urticaria, dermatitis, pruritus, asthma, photosensitivity, and angioneurotic oedema have been reported.
Other reported reactions: Leukopenia and agranulocytosis, usually when promethazine has been used in association with other known toxic agents; anaphalaxis; thrombocytopenic purpura; obstructive jaundice; tissue necrossis following subcutaneous injection, nasal stuffiness; and dry mouth.
The preferred route of administration of DBL® Promethazine Hydrochloride Injection BP is by deep intramuscular injection. Intramuscular injection may be painful.
Intravenous administration of this product is generally well tolerated, however extreme care must be taken to avoid extravasation or intra-arterial injection (see Contraindications). When given intravenously DBL® Promethazine Hydrochloride Injection BP 25mg/1mL should be diluted 1 in 10 with water for injections or preferably given through the tubing of a freely flowing I.V. infusion. It should be injected slowly at a rate of administration not greater than 25mg/minute (ie. 10mL/minute of dilute solution. Rapid intravenous infusion may cause a transient fall in blood pressure. Promethazine should not be given intra-arterially or subcutaneously (see Contraindications).
Adults: 25mg-50mg by deep intramuscular injection or slow intravenous injection; may be repeated within two hours if necessary. Maximum dose up to 150mg daily.
Antiemetics should not be used in vomiting of unknown etiology in children and adolescents (See precautions).
In established nausea or vomiting due to causes other than motion sickness:
Adults: 12.5 - 25mg, by intramuscular or intravenous injection, every four hours as needed.
Children: 5-12 yrs old 12.5mg by intramuscular injection.
Adults: 25-50mg by intramuscular or intravenous injection.
Children: When oral route is not possible:
2-5 yrs old 7.5 - 10mg by intramuscular injection
6-10 yrs old 10 - 12.5mg by intramuscular injection
Adults: 25-50mg by intramuscular or intravenous injection, usually with pethidine and atropine one hour before surgery.
Early stages of labour: 50 mg, by intramuscular injection. Established labour: 25-75mg, by intramuscular or intravenous injection, with an appropriately reduced dose of an opioid analgesic. May be repeated once or twice at four hourly intervals during the course of the labour, if necessary. Total dose should not exceed 100mg in 24 hours.
Symptoms of overdose range from mild depression of the CNS and cardiovascular system (drowsiness, bradycardia, tachycardia, and transient increases in blood pressure) to profound hypotension, respiratory depression, and unconsciousness. Paradoxical CNS stimulation (hallucinations, seizures, nightmares and trouble in sleeping) may be evident, especially in children and the elderly. Anticholinergic symptoms (severe dryness of mouth, nose or throat, flushing or redness of face, trouble in breathing), and extrapyramidal effects (muscle spasms, especially of the neck and back, restlessness tic-like movements of head and face, trembling of hands) may occur.
Treatment of promethazine overdosage is similar to that of other phenothiazine derivatives. Symptomatic supportive therapy is indicated and general physiologic measures such as maintenance of adequate ventilation should be instituted if necessary. Analeptics may cause convulsions and should not be used. Convulsions may be controlled with diazepam or barbiturates. Anticholinergic antiparkinsonism agents may be used to treat severe extrapyramidal reactions. Severe hypotension may respond to administration of noradrenaline or phenylephrine, but should not be treated with adrenaline because it may lower the blood pressure further.
Store below 25°C. Protect from light.
Prescription Only Medicine
DBL® Promethazine Hydrochloride Injection B.P. is available as follows:
Promethazine Hydrochloride 50mg/2mL 5 x 2mL Ampoules
Hospira NZ Limited
23 Haining Street
Te Aro
Wellington
New Zealand
23 May 2008
DBL® is a registered trade mark of Hospira Australia Pty Ltd.