Dimenhydrinate

Pronunciation: dye-men-HYE-dri-nate.

Generic name: dimenhydrinate
Drug class: Antihistamine-based antiemetic
Form: Tablet, chewable tablet, or syrup, depending on product
Route: Oral
Legal status: Available over-the-counter in the United States for oral use. This dossier found no standalone dimenhydrinate product registered in the United Kingdom; only a combination product with cinnarizine was identified there.

Availability and supply rules vary by country

Trade names by country: United States · Canada

What dimenhydrinate is and how it works

Dimenhydrinate is an antihistamine used as an antiemetic (anti-nausea medicine), mainly to prevent and treat motion sickness. (1)

It is available over-the-counter in the United States. It commonly causes drowsiness and has several conditions that require checking with a doctor or pharmacist first.

Mechanism of action: how dimenhydrinate works

Dimenhydrinate is an H1-antihistamine antiemetic; this OTC Drug Facts label does not provide detailed pharmacology beyond that classification. (1)

What dimenhydrinate is used for

Prevention and treatment of motion sickness

Used for prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness. For prevention, it is generally taken 30 minutes to 1 hour before travel begins. (1)

Before taking dimenhydrinate

Do not take / not appropriate for

Do not give to children under 2 years of age unless a doctor directs it. (children under 2) (1)

Tell your clinician about

A breathing problem such as emphysema or chronic bronchitis.
Glaucoma.
Difficulty urinating due to an enlarged prostate.
Whether you are taking a sedative or tranquilliser.
Pregnancy or breastfeeding.

(1)

How to take dimenhydrinate

Take exactly as directed on the product label or by your doctor.
For motion sickness prevention, take the first dose 30 minutes to 1 hour before travelling, then as needed.
Avoid alcohol while taking dimenhydrinate.
Use caution when driving or operating machinery, since marked drowsiness can occur.

(1)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1)

Missed dose

Take as directed on the product label or by your doctor. Do not take extra doses to make up for one you think you missed; ask a pharmacist if you are unsure.

Overdose

Contact a poison control centre or emergency service immediately if an overdose is suspected, even without symptoms. (1)

Side effects

Drowsiness is the most commonly reported effect and can be marked.

Drowsiness

What to notice: Can be pronounced ("marked drowsiness") in some people.

What to do: Avoid driving or operating machinery until you know how it affects you, and avoid alcohol and other sedating medicines. (1)

Difficulty urinating

What to notice: New or worsening difficulty passing urine.

What to do: Contact a doctor or pharmacist promptly; a clinician will decide whether dimenhydrinate needs to be stopped. (1)

Serious warnings

Overdose — emergency

Symptoms: Taking more than the directed dose.

Action: Contact a poison control center or emergency service immediately, even without symptoms. (1)

Liver function changes —

Action: Seek immediate medical attention if signs of allergic reaction or liver problems occur. Contact your healthcare provider before stopping treatment.

Interactions

Medicine or test	Effect	Action
Sedatives, tranquillisers, and alcohol	Combined use can increase drowsiness and impairment.	Ask a doctor or pharmacist before combining, and avoid alcohol while taking dimenhydrinate. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Glaucoma, breathing problems, or prostate enlargement

Ask a doctor before use if you have glaucoma, a breathing problem such as emphysema or chronic bronchitis, or difficulty urinating due to an enlarged prostate. (1)

Pregnancy and breastfeeding

Ask a health professional before use if you are pregnant or breastfeeding. (1)

Children

Do not use in children under 2 years old unless a doctor directs it. Lower, age-banded doses apply to children 2 to under 12; follow the exact product label. (1)

Monitoring

Before starting

Confirm age and screen for glaucoma, breathing problems, prostate-related urinary difficulty, and use of sedatives or tranquillisers.

During treatment

Watch for marked drowsiness, and avoid alcohol or other sedating medicines.
Seek medical advice for difficulty urinating.

(1)

Storage

Store at controlled room temperature, protected from moisture, out of reach of children.

Study the drug class: Antihistamines

Professional information

Clinician-facing context only. Use the current local product information for exact dosing.

United States (OTC Drug Facts label)

Indication: Motion sickness

Dose summary: Adults and children 12+: 1-2 tablets (50-100 mg) every 4-6 hours, not exceeding 8 tablets (400 mg) in 24 hours. Children 6 to under 12: 1/2-1 tablet every 6-8 hours, not exceeding 3 tablets in 24 hours. Children 2 to under 6: 1/2 tablet every 6-8 hours, not exceeding 1.5 tablets in 24 hours. Under 2: doctor-directed only.

Renal context: No renal/hepatic-impairment-specific adjustment is described in the OTC label reviewed. (1)

Mechanism of action

Hepatic guidance

Use local product information and clinical judgement; this page does not provide impairment-specific dosing.

Overdose note

Manage per local poison-control and emergency guidance; this OTC label does not itemize specific overdose toxicity details. (1)

Frequently asked questions

What is dimenhydrinate used for?

dimenhydrinate is prescribed for approved indications. Always follow your healthcare provider's guidance.

What are the side effects of dimenhydrinate?

Common side effects may include gastrointestinal symptoms and headache. Serious side effects require immediate medical attention.

Can I take dimenhydrinate with other medications?

Always inform your healthcare provider about all medications you are taking, including over-the-counter products and supplements.

What is the mechanism of action of dimenhydrinate?