Diphenidol (Oral)

Diphenidol is a medicine prescribed for treating patients who experience nausea, vomiting or dizziness due to the presence of certain medical conditions.


Diphenidol is a medicine that falls into the class of antiemetic agents. It is available as a tablet, by doctor's prescription only, and is safe to use in adults and children.

Antiemetic agents work by blocking receptors in the brain that trigger vomiting and feelings of nausea and dizziness. How diphenidol functions in the body to provide the desired relief is not clearly established in clinical studies. The tablet is believed to provide relief by suppressing the feelings of nausea and dizziness and the reflex to vomit.

This medicine will add to the effects of alcohol or medications that cause drowsiness or reduce alertness.

There is also a risk of increased adverse effects if it is used to treat patients who have other medical conditions, such as kidney disease or enlarged prostate.

The medicine is not recommended for treating the type of nausea and vomiting that occur during pregnancy.

Conditions Treated

Type Of Medicine

Antiemetic agent

You should consider the potential benefits and risks of using diphenidol. Your doctor may help you decide if it is safe for you and how to treat you.

Tell your doctor if you are allergic to the medicine or have had an unusual reaction to it. Some patients may also be allergic to inactive ingredients in the medication. In discussing allergies, tell your doctor of any allergy to foods, preservatives, dyes or animals.

Also tell your doctor if you are pregnant or breastfeeding.

Certain medications or medical conditions may affect the way the tablet works. Tell your doctor of all medications you are taking or plan to take. These include prescription and over-the-counter medicines (OTCs), vitamins, nutritional supplements, and herbal products.

Special precautions may be needed when deciding to treat children, elderly patients, and pregnant or breastfeeding women. Enough information is not available to determine the full effect of the drug, or the risks posed, when used in these patients.

No specific information is available to determine the safe use of the medicine for treating dizziness in children. Its safety and efficacy have not been established for treating vomiting and nausea in children weighing under 22.8 kilograms (50 pounds).

Side Effects

Most, if not all, medicines cause side effects. Some are needed; others are unwanted. Side effects may also be mild or rare and may go away on their own. Others may be severe or serious and require urgent medical attention.

Side effects may not occur all at once in a single patient, but some that do occur may require medical attention.

Call your doctor right away if you experience any of the following side effects:

Rarely occur

  • Hallucinations (hearing, seeing or feeling things that are not actually there)
  • Confusion

The following side effects may not need medical attention if they occur. However, if they become bothersome, worse, or do not go away tell your doctor.

More commonly occur

  • Drowsiness

Less commonly occur

  • Headache
  • Dizziness
  • Heartburn
  • Nervousness
  • Stomach pain
  • Upset stomach
  • Restlessness
  • Blurred vision
  • Rash on the skin
  • Trouble sleeping
  • Dryness of the mouth
  • Feeling unusually tired or weak

Some patients may experience other side effects not listed in this guide. Tell your doctor if you notice other unusual symptoms. You can ask your doctor or healthcare professional how to reduce or prevent side effects.

You may call the FDA at 1-800-FDA-1088 to report side effects.


The exact dose of your medicine will be determined by your doctor. Follow all directions for taking your tablet as stated on the prescription label. Also follow any other directions given to you by your doctor or pharmacist.

This dosing guide contains the average recommended dose for adults. You should not change your dose, unless approved by your doctor.

For nausea, vomiting or dizziness

Adults: Take 25 to 50 milligrams (mg) every four hours as needed.

Children: Treatment must be determined by a doctor, and is based on body weight.

Missed dose

If you miss a dose of your medicine, take it as soon as possible. If it is almost time to take your next dose, skip the missed dose and take your next dose on schedule. Do not take an extra dose to make up for a missed dose.


Call your local poison control center at 1-800-222-1222 if you overdose on this drug. If the patient collapses or is not breathing, call 911.

Also call 911 and seek urgent medical attention if you experience any of the following symptoms of overdose:

  • Trouble with breathing (including shortness of breath); or
  • Tiredness or weakness that is unusual and severe; or
  • Severe drowsiness


Other medicines

It may not be safe to use other medications (both prescription and non-prescription) or certain health products while taking diphenidol. Before and during treatment, ensure you tell your doctor of all medicines and products you are taking or plan to take.

Your doctor may still decide to treat you, but change one or more of your medications or the dose.

This can help your doctor provide a treatment plan designed to avoid or reduce the chance of adverse interaction with this medicine.

Food, alcohol, and tobacco

Your doctor may warn you about the use of certain types of food during treatment. Alcohol and tobacco may also not be safe to use during your treatment. Alcohol is known to affect the way this medication works and can cause severe dizziness or drowsiness.

Other medical problems

Precautions may be necessary when treating patients who have other medical conditions. Sometimes, it is not at all safe to use certain medications in such patients. Your doctor may decide if is best for your health to treat you with diphenidol, even though you may have other medical conditions.

Ensure you tell your doctor of any other medical problem you have, especially the following. Diphenidol may cause them to become worse.

There is an increased risk of side effects if patients with the following medical problems are treated with this medicine. This is because the medicine takes a longer time to be removed by their body.

  • Urinary tract blockage
  • Kidney disease

There may be other medical problems which may interact with the drug but are not listed in this guide. You may ask your doctor for more information.


  • Use this medicine only if it is prescribed for you for treating nausea, vomiting, or dizziness.
  • Use your treatment exactly as directed by your doctor, pharmacist, and the prescription label.
  • Do not take less or more of the tablet, or more often than directed, unless your doctor tells you to.
  • Do not stop using the medicine unless your doctor tells you to.
  • This medicine causes dizziness and drowsiness. Do not drive a vehicle or operate machinery until you know how this medicine affects you.
  • Avoid the use of alcohol or taking other medicines that may increase the risk of drowsiness and dizziness, such as CNS depressants. Anesthetics, sedatives, and antihistamines are examples of CNS depressants.
  • Do not take this drug unless you tell your doctor of any other medical condition you may have.


Store the medicine in a closed container at room temperature, preferably between 59 and 86 degrees F (15 and 30 degrees C). Avoid exposure to heat, moisture, and direct light.

Do not store the medicine in the bathroom. Do not freeze.

Keep out of the reach of children.

Throw away medicine that expired or is no longer needed. You may ask your healthcare professional or local waste disposal agency how to safely dispose of it.


Diphenidol has been established as a safe and effective drug for treating nausea, dizziness, and vomiting caused by certain medical problems. This is the case despite medical data has not clearly shown how the drug affects the body to provide relief.

Its safety and efficacy are proven in adults and in children. But children under 50 lbs may not be treated with the medicine. In addition, the medication cannot be prescribed to treat nausea and vomiting triggered by pregnancy.

This medicine has the potential to affect the central nervous system, thereby causing some serious side effects. They include confusion and hallucinations, and need immediate medical attention when they occur.

For these reasons, the drug should be used with caution when treating patients who are more likely to be affected. Elderly patients are known to be at a higher risk for these side effects.

This medication is also affected by alcohol use, as well as other medications, particularly central nervous system depressants. Dizziness and drowsiness are among the side effects of these depressants.

As a result, using them together with diphenidol increases the risk of side effects and may cause some of them to become serious.