dimenhydrinate

Dimenhydrinate is a medication used to prevent and treat nausea, vomiting, and vertigo associated with motion sickness. Dimenhydrinate is a combination of diphenhydramine, an antihistamine drug, and 8-chlorotheophylline, a stimulant with effects similar to caffeine. The principal therapeutic effects are from diphenhydramine, while 8-chlorotheophylline is thought to reduce the drowsiness caused by diphenhydramine. Dimenhydrinate is available on prescription and also over the counter (OTC).

Diphenhydramine inhibits histamine H1 receptors, protein particles on cell membranes that initiate an inflammatory response when activated by histamine. Diphenhydramine is a first-generation antihistamine that can cross the blood-brain barrier and enter the central nervous system (CNS). Diphenhydramine blocks histamine activity in the CNS, which inhibits vestibular stimulation, reducing the sensation of dizziness and nausea. It also suppresses the CNS, causing drowsiness.

Dimenhydrinate is used for the prevention and treatment of nausea, vomiting and vertigo associated with the following conditions:

FDA-approved:

• Motion sickness

Off-label:

• Postoperative recovery
• Meniere’s disease
• Radiation sickness
• Use of other drugs
• Acute vertigo episodes
• Severe and refractory pregnancy-associated nausea and vomiting

• Do not use dimenhydrinate in patients with hypersensitivity to any component of the formulation.
• Do not use dimenhydrinate to treat nursing mothers, and newborn or premature infants.
• Do not administer dimenhydrinate to children below 2 years of age, unless directed by a pediatrician.
• Do not use dimenhydrinate concurrently or within 14 days after treatment with monoamine oxidase inhibitor (MAOI) antidepressant medications.
• Dimenhydrinate may mask early signs of toxicity to the ear (ototoxicity), if given concurrently with ototoxic drugs.
• Dimenhydrinate can cause CNS depression and impair mental and physical abilities required for hazardous tasks. Caution patients appropriately.
• Use with caution in patients with any of the following conditions:
  • Cardiovascular diseases including high blood pressure (hypertension), irregular heart rhythms (arrhythmia) and heart disease from impaired blood flow (ischemic heart disease)
  • Liver function impairment
  • Increased intraocular pressure or glaucoma, a condition that damages the optic nerve
  • Respiratory conditions such as emphysema, asthma or chronic bronchitis
  • Prostate enlargement and associated urinary obstruction
  • Stenosing peptic ulcer
  • Pyloroduodenal obstruction
  • Seizure disorders
  • Thyroid dysfunction
• Use with caution in older adults, they may be more sensitive to adverse effects.
• Some formulations may contain phenylalanine which should be avoided in patients with phenylketonuria, a disorder with inability to metabolize phenylalanine.
• Some formulations may contain sodium benzoate/benzoic acid, a metabolite of benzyl alcohol in newborn babies. Large amounts of benzyl alcohol have been associated with potentially fatal toxicity (gasping syndrome) in neonates.
• Some formulations may contain propylene glycol which can be toxic in large quantities.
• Some formulations contain polysorbate 80 which can cause hypersensitivity reactions in some people.
• Dimenhydrinate has a potential for abuse because of its hallucinogenic and euphoric effects. Discontinuation after chronic abuse can cause withdrawal symptoms.
• There have been rare reports of life-threatening skin reactions including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme. Discontinue if skin rash develops and consult with your physician.

Common side effects of dimenhydrinate include:

• Central nervous system (CNS) depression
• Paradoxical CNS stimulation
• Dizziness
• Drowsiness
• Sedation
• Headache
• Insomnia
• Lethargy
• Excitement
• Nervousness
• Restlessness
• Euphoria
• Delirium
• Irritability
• Toxic psychosis
• Disturbed coordination
• Involuntary facial movements (facial dyskinesia)
• Abnormal skin sensation (paresthesia)
• Tremor
• Seizure
• Muscular weakness
• Tightness of chest
• Palpitation
• Rapid heart rate (tachycardia)
• Irregular heart rhythm (arrhythmia)
• ECG changes
• Low or high blood pressure (hypotension/hypertension)
• Nausea
• Vomiting
• Epigastric distress
• Diarrhea
• Constipation
• Loss of appetite (anorexia)
• Dry mouth (xerostomia)
• Dryness of mouth, nose and throat
• Thickening of bronchial secretions
• Nasal stuffiness
• Wheezing
• Skin rash
• Eczema
• Itching (pruritus)
• Blurred vision
• Visual disturbances
• Double vision (diplopia)
• Ringing in the ears (tinnitus)
• Acute inner ear infection (labyrinthitis)
• Vertigo
• Chills
• Sweating
• Feeling faint
• Painful urination (dysuria)
• Urinary retention
• Impotence
• Early occurrence of periods
• Impaired bile flow (cholestasis)
• Liver inflammation (hepatitis)
• Impaired liver function
• Liver failure
• Jaundice
• Blood disorders including
• Severely low count of granulocyte immune cells (agranulocytosis)
  • Low red blood cell count due to rapid destruction (hemolytic anemia)
  • Low count of white cells (leukopenia)
  • Low platelet count (thrombocytopenia)
  • Low count of all types of blood cells (pancytopenia)

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

• Dimenhydrinate has a potential for abuse because of its hallucinogenic and euphoric effects. Discontinuation after chronic abuse can cause withdrawal symptoms such as lethargy, agitation, hostility, hallucinations, confusion, aggression and nausea/vomiting.
• Dimenhydrinate overdose can cause drowsiness, convulsions, respiratory depression and coma in adults, and hallucinations, convulsions and death in children and infants. Overdose is treated with symptomatic and supportive care, including mechanical ventilation.

Injectable solution

• 50 mg/mL

Tablet

• 50 mg

Tablet, chewable

• 50 mg

Adult:

Prevention of Motion Sickness

• 50-100 mg oral/intravenous/intramuscular (PO/IV/IM) every 4-6 hours as needed, 30 minutes before exposure to motion; not to exceed 400 mg/day

Meniere's Disease (Off-label)

• 25-50 mg orally every 8 hours for maintenance
• 50 mg IM for acute attack

Administration

• IV: 50 mg in 10 mL normal saline (NS) over 2 minutes

Pediatric:

Prevention of Motion Sickness

• General dose: 1.25 mg/kg or 37.5 mg/sq. meter IV/IM every 6 hours; not to exceed 300 mg/day  
• Children 2-6 years old: 12.5-25 mg orally every 6-8 hours; no more than 75 mg/day
• Children 6-12 years old: 12.5-25 mg every 6-8 hours; no more than 150 mg/day
• Children above 12 years old: Same as adult dosing

Addiction/Overdose

• Dimenhydrinate has a potential for abuse because of its hallucinogenic and euphoric effects. Discontinuation after chronic abuse can cause withdrawal symptoms such as lethargy, agitation, hostility, hallucinations, confusion, aggression and nausea/vomiting.
• Dimenhydrinate overdose can cause drowsiness, convulsions, respiratory depression and coma in adults, and hallucinations, convulsions and death in children and infants. Overdose is treated with symptomatic and supportive care, including mechanical ventilation.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Dimenhydrinate has no severe interactions with other drugs.
• Serious interactions of dimenhydrinate include:
  • calcium/magnesium/potassium/sodium oxybates
  • eluxadoline
  • metoclopramide intranasal
  • olopatadine intranasal
  • pitolisant
  • secretin
  • sodium oxybate
• Dimenhydrinate has moderate interactions with at least 205 other drugs.
• Dimenhydrinate has minor interactions with at least 45 other drugs. 

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• Dimenhydrinate use during pregnancy was not associated with any fetal abnormalities. Dimenhydrinate may be used for adjunctive treatment of pregnancy-associated nausea and vomiting.
• Dimenhydrinate is excreted in breastmilk. Discontinue the drug or nursing, after considering the importance of the drug to the mother, and the benefits of breastfeeding and risks of drug exposure to the breastfed infant.

• Take dimenhydrinate exactly as prescribed or as per label directions.
• Dimenhydrinate may cause drowsiness. Avoid hazardous tasks such as driving or operating heavy machinery while taking dimenhydrinate.
• Avoid taking tranquilizers, sedatives or alcohol while taking dimenhydrinate, it can increase drowsiness.
• Store dimenhydrinate safely out of reach of children.
• In case of overdose, seek immediate medical help or contact Poison Control.