Action And Clinical Pharmacology: While the precise mode of action of dimenhydrinate is not known, it has a depressant action on hyperstimulated labyrinthine functions or associated neural pathways.
Indications: Prevention and relief of motion sickness and the nausea or vomiting incident to these conditions. The treatment or prophylaxis of the nausea and vomiting of radiation sickness, postoperative vomiting, and drug-induced nausea and vomiting; also for the symptomatic treatment of nausea, vomiting and vertigo due to M©nire’s disease and other labyrinthine disturbances.
Manufacturers’ Warnings In Clinical States: Antiemetics must be used with caution since they may mask the presence of underlying organic abnormalities or the toxic effects of certain antibiotics and other drugs, particularly those drugs causing ototoxicity.
Occupational Hazards: Patients receiving dimenhydrinate should be cautioned against operating automobiles or dangerous machinery because of the drowsiness associated with the drug. If drowsiness is excessive, dosage should be reduced.
Precautions: Rarely, prolonged therapy with antihistaminic drugs can produce blood dyscrasia.
Dimenhydrinate should be used with caution in patients in whom anticholinergics may aggravate other clinical conditions.
An additive effect may be produced if alcohol or other CNS depressant drugs are given concomitantly with dimenhydrinate.
Pregnancy: The use of dimenhydrinate by women who are pregnant or may become pregnant requires that the potential benefits be weighed against the potential hazards.
Adverse Reactions: Drowsiness may be experienced by some patients, especially at high dosages. Dizziness may also occur. Symptoms of dry mouth, lassitude, excitement and nausea have been reported.
Symptoms And Treatment Of Overdose: Symptoms: Drowsiness is the usual clinical side effect. Convulsions, coma and respiratory depression may occur with massive overdosage.
Children are very susceptible to the convulsant action of antihistamines and doses of 150 to 800 mg of diphenhydramine in children aged 1 1/2 to 3 1/2 have been reported to produce convulsions. A suspected dose of 700 mg of dimenhydrinate produced death in a 22-month-old boy and a dose greater than 800 mg directly caused death in a 2-year-old boy. There has been a report of hallucinations after ingesting 500 mg of diphenhydramine HCl, as well as a few reports of delirium and hallucinations following the ingestion of approximately 750 mg of dimenhydrinate. A single case of severe delirium, closely resembling atropine poisoning and with possible extrapyramidal symptoms, following ingestion of a massive overdose of dimenhydrinate taken by an 18-year-old man has been reported.
Treatment: No specific antidote. Cautiously administer short-acting barbiturates, or other anticonvulsants i.m. or i.v. if convulsions occur. Other treatment is supportive and resuscitative.
Dosage And Administration: Adults: Nausea or vomiting may be expected to be controlled for approximately 4 hours with 25 to 50 mg of dimenhydrinate, and prevented by a similar dose every 4 hours. This dosage regimen may cause some degree of drowsiness in some patients and 100 mg every 4 hours may be given in conditions in which drowsiness is not objectionable or is even desirable.
I.M.: 1 to 2 mL (50 to 100 mg) of the 50 mg/mL solution are injected every 4 hours as needed.
I.V.: The 10 mg/mL injection should be given slowly. The preparation designed for i.m. use (50 mg/mL) must not be used i.v. unless it has been diluted at least 1:10 with a compatible i.v. solution, such as Sodium Chloride Injection USP. The maximum daily dose should not exceed 300 mg for adults.
Children: I.M.: 6 to 8 years: 12.5 to 25 mg, 2 or 3 times daily; 8 to 12 years: 25 mg to 50 mg, 2 or 3 times daily; over 12 years: 50 mg, 2 or 3 times daily.
I.V.: The i.v. dose in children has not been established.
Dimenhydrinate should not be given parenterally to neonates.
Availability And Storage: 10 mg/mL Injection: Each mL of solution contains: dimenhydrinate 10 mg in water for injection, ethanol and HCl to adjust to pH 6.4 to 7.2. Polyamp Duofit units of 5 mL for i.v. use.
50 mg/mL Injection: Each mL of solution contains: dimenhydrinate USP 50 mg in a mixture of propylene glycol and water for injection and HCl to adjust to pH 6.4 to 7.2. Polyamp Duofit units of 1 mL for i.m. and, when appropriately diluted, i.v. use.
Substances which are physically incompatible with injectable solutions of dimenhydrinate include: phenothiazine derivatives, aminophylline, ammonium chloride, sodium amobarbital, diphenylhydantoin, heparin, hydrocortisone sodium succinate, pentobarbital, phenobarbital, thiopental and certain antibiotics, e.g. tetracycline HCl.
Do not use if solution is cloudy or contains a precipitate.
Store at controlled room temperature 15 to 30°C. Protect from freezing.
DIMENHYDRINATE INJECTION Astra Antiemetic