Dimenhydrinate belongs to a group of medications called antiemetics. This medication is used to prevent and treat motion sickness as well as nausea and vomiting associated with various conditions such as chemotherapy, radiation, and surgery. It is also used to treat nausea and spinning sensations (vertigo) due to Ménière's disease and other conditions that cause these symptoms.

Dimenhydrinate works to relieve or prevent nausea and vomiting by affecting the vomiting centre in the brain. Most people can expect some relief of nausea and vomiting within one hour of taking any form of dimenhydrinate. It works to relieve vertigo by affecting the brain and the inner ear.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are using this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

Motion sickness, nausea, vomiting, dizziness, and spinning sensation (vertigo): The usual adult dose of the tablets is 50 mg to 100 mg taken every 4 hours as needed. Do not take more than 400 mg in a 24-hour period. The dose of the long-acting form of dimenhydrinate tablets is 100 mg every 8 to 12 hours, with a maximum of 3 tablets in a 24-hour period. The usual adult dose of dimenhydrinate suppository is 50 mg to 100 mg every 6 to 8 hours as needed.

If you are taking dimenhydrinate for motion sickness, the first dose should be taken at least 30 minutes and preferably 1 to 2 hours before departure.

Pre-radiation therapy (radiation sickness): In adults, 50 mg to 100 mg of dimenhydrinate may be given as a suppository or injection, 30 to 60 minutes before receiving radiation therapy. This dose may be repeated as needed up to a maximum of 400 mg over a 24-hour period.

Surgery: To control nausea and vomiting following surgery for adults, the usual dose is 50 mg to 100 mg taken by mouth or 50 mg of injection into a muscle before surgery. After surgery, similar doses can be used up to a maximum dose of 400 mg in a 24-hour period.

Children: Follow the dosing instructions provided to you by your doctor or pharmacist or the ones provided with the product being used. This medication should not be used for children or infants under two years old.

For children 2 to 6 years old, the dose of dimenhydrinate liquid or tablets is 15 mg to 25 mg every 6 to 8 hours as needed to a maximum of 75 mg in a 24-hour period. For the suppositories, the dose in this age group is 12.5 mg to 25 mg. Do not give more than one dose of the suppository form unless recommended by your doctor.

For children 6 to 8 years old, the dose of dimenhydrinate liquid or tablets is 25 mg to 50 mg every 6 to 8 hours as needed to a maximum of 150 mg in a 24-hour period. For the suppositories, the dose in this age group is 12.5 mg to 25 mg every 8 to 12 hours as needed.

For children 8 to 12 years old, the dose of dimenhydrinate liquid or tablets is 25 mg to 50 mg every 6 to 8 hours as needed to a maximum of 150 mg in a 24-hour period. For the suppositories, the dose in this age group is 25 mg to 50 mg every 8 to 12 hours as needed.

For children 12 years of age and older, the dose of dimenhydrinate liquid or tablets is 50 mg every 4 to 6 hours as needed to a maximum of 300 mg in a 24-hour period. For the suppositories, the dose in this age group is 50 mg every 8 to 12 hours as needed.

Chewable tablets and liquid are available for children or adults who are unable to swallow the tablets. When using the liquid, use an oral syringe to measure each dose of the liquid as it gives a more accurate measurement than household teaspoons.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

It is important to use this medication exactly as recommended by your doctor or pharmacist. If you are taking dimenhydrinate regularly and miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature and keep it out of the reach of children.

Do not use this medication if you:

• are allergic to dimenhydrinate or any ingredients of the medication
• are taking a MAO inhibitor (e.g., phenelzine, tranylcypromine, moclobemide) or have taken a MAO inhibitor within the past 2 weeks
• have chronic lung diseases such as chronic bronchitis or emphysema
• have difficulty passing urine due to an enlarged prostate (prostatic hypertrophy)
• have glaucoma

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is used in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who uses this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people using this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• dizziness
• drowsiness
• dry mouth
• excitement (especially in children)
• lack of energy

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• blurred vision or any change in vision
• confusion
• difficulty passing urine
• skin rash

Stop taking the medication and seek immediate medical attention if any of the following occur:

• rapid, shallow breathing
• seizure
• symptoms of a severe allergic reaction (e.g., difficulty breathing; hives; swelling of the face, mouth, tongue, or throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abuse and dependence: At higher doses, this medication can cause hallucinations (seeing or hearing things that aren't there) and euphoria (feeling intense happiness and excitement). Dimenhydrinate is known to be misused for these effects. This can lead to overdose and be life-threatening.

If dimenhydrinate is used for a long period of time, you may experience withdrawal effects such as agitation, hostility, confusion, nausea, and vomiting if it is suddenly stopped . If you have been taking this medication for a long time, talk to your doctor about stopping this medication gradually.

Alcohol: Alcohol may add to the side effects of dimenhydrinate (e.g., drowsiness) and should be avoided when using this medication.

Drowsiness: This medication can cause drowsiness, affecting your ability to drive or operate machinery. Avoid these and other hazardous tasks until you know how dimenhydrinate affects you.

Glaucoma: This medication may cause the symptoms of glaucoma (increased pressure in the eye) to become worse. If you have glaucoma, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Report any changes in vision to your doctor as soon as possible while you are taking this medication.

Heart disease: Although not common, dimenhydrinate can cause changes to heart rhythm and blood pressure. If you have any heart conditions, ask your health care professional if any special monitoring is required.

Phenylketonuria: The chewable tablet form of dimenhydrinate may contain aspartame, an ingredient that cannot be broken down in the body by people who have phenylketonuria (a condition where you are lacking the enzyme needed to break down phenylalanine). People with phenylketonuria should take another form of dimenhydrinate.

Prostate problems: This medication may cause the symptoms of an enlarged prostate to become worse. If you have an enlarged prostate, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Seizures: If you have a seizure disorder or a history of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and are taking dimenhydrinate, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under two years of age.

There may be an interaction between dimenhydrinate and any of the following:

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.