What is Dimenhydrinate?

Dimenhydrinate is a first generation H1 antihistamine and belongs to the group of ethanolamine derivatives. The mechanism of action of the drug is to compete with histamine at the H1 receptor. In addition to its antihistamine effects, dimenhydrinate also has anticholinergic, sedative, and antiemetic effects. Dimenhydrinate is used mainly as a prophylactic to prevent vomiting caused by motion sickness. The exact mechanism of these effects is unknown, but may be due to dimenhydrinate helping to reduce vestibular stimulation, acting primarily on the cochlea, and when used in high doses can affect the semicircular canals of the ear. in. The antiemetic effect may also be due to effects on chemoreceptors. Some studies have suggested that inhibition of acetylcholine is the main mechanism of action, since stimulation of acetylcholine in the vestibular and reticular systems may be responsible for nausea and vomiting while riding. The CNS depressant effect usually subsides after a few days of treatment and the antiemetic effect may decrease somewhat after prolonged use. In summary, the drug is indicated in the following cases:
Prevention and treatment of nausea, vomiting and dizziness during motion sickness. Treatment of vomiting and vertigo in Ménière's disease and other vestibular disorders.

Hypersensitivity to dimenhydrinate or to other antihistamines. Patient with angle-closure glaucoma. Urinary retention is related to pathology of the urethra - prostate. Children under 2 years old.

3.1. Prevention and treatment of nausea, vomiting, dizziness caused by motion sickness Adults and children The first dose must be taken about 30 minutes before departure. Adults and children over 12 years old use 50-100 mg / time, every 4-6 hours as needed, not more than 400 mg / day. Children 6 - 12 years of age: 25 - 50 mg/time, every 6 - 8 hours as needed and up to 150 mg per day. Children from 2 to 6 years old: orally 12.5 - 25 mg/time, every 6 - 8 hours as needed, up to 75 mg per day 3.2. Symptomatic treatment of Ménière's disease 25 - 50 mg each time, 3 times a day for maintenance treatment or 50 mg intramuscularly in acute attacks.

Some unwanted side effects may be encountered during the use of Dimenhydrinate drugs as follows:
Cardiovascular: Tachycardia Central nervous system: Dizziness, drowsiness, excitement, headache, insomnia , somnolence, anxiety, restlessness Dermatology: Skin rash Digestive: Anorexia, epigastric pain, nausea, vomiting Genitourinary system: Difficult urination Ophthalmology: Blurred vision Respiratory: increased secretions bronchial fluid

Some notes during the use of Dimenhydrinate drugs are as follows:
Central nervous system depression: May cause central nervous system depression, impairing physical or mental abilities. Therefore, patients must be warned about performing tasks that require mental alertness (eg, operating machinery or driving a vehicle). Other CNS effects that may be observed, particularly at higher doses, include euphoria, hallucinations, confusion, paranoia, and transient amnesia. Skin Reactions: Rare cases of serious skin reactions (eg, Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme) have been reported. Discontinue use if skin rash occurs and consult a doctor or pharmacist. Cardiovascular disease: Use with caution in patients with cardiovascular disease (including arrhythmias, hypertension, and ischemic heart disease). Hepatic impairment: Dimenhydrinate should be used with caution in patients with hepatic impairment. Glaucoma: Use with caution in patients with glaucoma Prostate hyperplasia/urinary tract obstruction: Use with caution in patients with prostatic hyperplasia and/or urinary tract obstruction. Duodenal Obstruction: Use with caution in patients with duodenal obstruction (including peptic ulcer). Respiratory disease: Use with caution in patients with a history of asthma or lower respiratory tract symptoms. Epilepsy: Caution should be exercised when dimenhydrinate is given to patients with seizure disorders. Thyroid dysfunction: Dimenhydrinate should be used with caution in patients with thyroid dysfunction. Concomitant use with antibiotics: Use caution if used with antibiotics that are potentially toxic to the ear. Dimenhydrinate may mask the symptoms of ototoxicity. Elderly: Use with caution in the elderly because patients may be more sensitive to the side effects of dimenhydrinate. Children: Antihistamines can cause irritation in young children, so care should be taken when using them. Pregnancy: Dimenhydrinate crosses the placenta. The risk of fetal abnormalities was not increased after maternal use of dimenhydrinate during any trimester of pregnancy. Therefore, dimenhydrinate can be used for the adjuvant treatment of nausea and vomiting during pregnancy. Lactation: Dimenhydrinate is present in breast milk. Drowsiness and irritability have been reported in breastfed infants exposed to antihistamines. The manufacturer recommends that the decision to continue or to discontinue breastfeeding during treatment should take into account the risk of exposure to the infant and the benefit of dosing to the mother. In general, if breastfed infants are exposed to first-generation antihistamines, they should be monitored for irritability or somnolence. Of note, antihistamines may reduce the mother's serum prolactin levels when administered before lactation begins. Drug Interactions: Concomitant use of dimenhydrinate with some other drugs may reduce the effectiveness or increase the side effects of the drug. Therefore, patients should be advised to inform their doctor of all medications and supplements they are using for appropriate advice and adjustment. In summary, Dimenhydrinate is an H1 antihistamine commonly used in the treatment of nausea, vomiting caused by motion sickness and some other conditions. The drug has a sedative effect causing sleep, so patients should be careful when performing tasks that require alertness such as operating machinery or driving.
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