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Mefloquine is used to prevent or treat malaria. It works by killing certain parasites that cause malaria. Common side effects of mefloquine include nausea and vomiting, stomach pain, and diarrhea. Contact your health care provider right away if you get anxiety, depression, dizziness, balance problems, ringing in your ears, or any vision changes.

Uses

What is mefloquine used for?

Mefloquine is commonly used to prevent or treat malaria caused by certain parasites.

Mefloquine may also be used for other conditions as determined by your health care provider.

How does mefloquine work (mechanism of action)?

Mefloquine works by killing certain parasites that cause malaria.

How is mefloquine supplied (dosage forms)?

Brands and other names

  • Lariam

Dosage forms and strengths

  • 250 mg oral tablets

How should I store mefloquine?

Mefloquine should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of mefloquine?

The most common side effects of mefloquine are listed below. These side effects may vary depending on the use of mefloquine for either treatment or prevention of malaria. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea
  • Vomiting
  • Diarrhea
  • Stomach pain
  • Headache
  • Dizziness
  • Muscle pain
  • Fever
  • Chills
  • Rash
  • Loss of appetite

There may be other side effects of mefloquine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of mefloquine?

While less common, the most serious side effects of mefloquine are described below, along with what to do if they happen.

Severe Allergic Reactions. Mefloquine may cause allergic reactions, which can be serious. Stop taking mefloquine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Nervous System Problems. Mefloquine can cause problems with your nervous system that may not go away even after you stop this medicine. Do not drive or do other activities that require coordination until you know how mefloquine affects you. Tell your health care provider right away if you have any of the following symptoms.

  • Dizziness
  • Feeling off balance
  • Ringing in your ears
  • Seizures
  • Trouble sleeping

Hallucinations or Psychotic-Like Behaviors. Mefloquine may cause hallucinations or psychotic-like behaviors. Tell your health care provider right away if you have any of the following symptoms, or if others have noticed these symptoms in you.

  • Hearing, seeing, smelling, tasting, or otherwise perceiving things that others do not
  • Delusional thoughts, such as false beliefs that you are being controlled
  • Feeling mistrust for others, or that others are out to get you
  • Disorganized thoughts, such as jumping between topics or having a hard time focusing
  • Sudden decline in self-care, such as personal hygiene or academic/work performance
  • Confusion
  • Aggressive behavior
  • Restlessness or anxiety

Suicidal Thoughts and Actions. Mefloquine may cause suicidal thoughts or actions in a small number of people. If you are about to harm yourself, call 911 or call or text 988, the Suicide & Crisis Lifeline. Call your health care provider right away if you have any of the following symptoms.

  • New or increased thoughts of suicide or death
  • Suicide attempt
  • New or increased feelings of anxiety, depression, or other unusual changes in mood or behavior

Eye Damage. Mefloquine may cause damage to your retina or to the nerve that lets your eyes send signals to your brain (optic nerve). Keep all appointments to have your eyes checked. Let your health care provider know right away if you have any changes to your vision. 

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking mefloquine. Call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Warnings & Precautions

Who should not use mefloquine?

Allergies to Ingredients. People who are allergic to any of the following should not take mefloquine.

  • Lariam
  • Mefloquine
  • Quinine
  • Quinidine
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific mefloquine products they stock.

Mental Health Conditions. You should not take mefloquine to prevent malaria if you have or have recently had mental health conditions such as depression, anxiety disorder, psychosis, or schizophrenia.

Seizures. You should not take mefloquine to prevent malaria if you have seizures or had them at one point.

What should I know about mefloquine before using it?

Do not take mefloquine unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share mefloquine with other people, even if they have the same condition as you. It may harm them.

Keep mefloquine out of the reach of children.

Take mefloquine after you eat your largest meal of the day. Take it with at least 8 oz (one cup) of water.

You can crush mefloquine tablets and mix them with a small amount of liquid, such as water, milk, or another beverage, if needed, just before taking the medicine.

Mefloquine can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how mefloquine affects you.

Malaria can be life-threatening. If you take mefloquine to help prevent malaria, use other methods to prevent mosquito bites. For example, use bug repellent, bed nets, and protective clothing. If you get a fever, seek medical care because you may have been exposed to malaria.

What should I tell my health care provider before using mefloquine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if mefloquine is right for you.

In particular, make sure that you discuss any of the following.

Vaccines. Talk with your health care provider about any vaccines that you may need. You should not receive certain vaccines right before or while using mefloquine. Tell your health care provider about any vaccines you have recently received or have scheduled.

Other Medicines and Supplements. Mefloquine may interact with other medicines and supplements. Before taking mefloquine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Heart problems, including a slow heart rate or arrhythmias
  • Liver problems
  • Seizures
  • Diabetes
  • Mental health conditions
  • Blood clotting problems

Pregnancy. It is not known if or how mefloquine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. If you can become pregnant, use effective birth control while you are taking mefloquine and for three months after your last dose. Talk to your health care provider about your birth control options. If you become pregnant, contact your health care provider right away.

Breastfeeding. Mefloquine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should stop breastfeeding or stop mefloquine.

Interactions

Does mefloquine interact with foods or drinks?

There are no known interactions between mefloquine and foods or drinks.

It is unknown if drinking alcohol will affect mefloquine. The risk of dizziness may be increased if you drink alcohol while taking mefloquine. In addition, heavy drinking can slow your immune response and make it harder for your body to fight infection.

Does mefloquine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking mefloquine.

  • Any medicine that can cause QT prolongation, which is a potentially dangerous heart rhythm problem, such as quinidine or quinine
  • Ketoconazole, which is a medicine used for fungal infections 
  • A beta-blocker, such as propranolol (Inderal LA, Innopran XL), which is a medicine that may be used for certain heart conditions or to lower blood pressure
  • A medicine for malaria, such as chloroquine or primaquine
  • A medicine used to control your heart rate or rhythm (antiarrhythmic)
  • A calcium channel blocker, such as diltiazem (Cardizem CD and others) or verapamil (Verelan, Verelan PM), which is a medicine used for high blood pressure or other conditions
  • An antihistamine, such as chlorpheniramine or diphenhydramine (Benadryl), which is a medicine commonly used to treat allergy symptoms
  • A tricyclic antidepressant, such as amitriptyline, nortriptyline, or protriptyline, even if it is not used for depression
  • A phenothiazine, such as chlorpromazine or prochlorperazine (Compro and others), which is a medicine that may be used to treat certain mental health conditions or severe nausea and vomiting
  • Any medicine for seizures, such as carbamazepine, phenobarbital,  phenytoin, or valproic acid
  • Rifampin (Rifadin), which is a medicine commonly used to treat an infection called tuberculosis
  • A blood thinner, which is a medicine used to treat or prevent blood clots

Many other medicines may alter the blood levels of mefloquine. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with mefloquine. Always check with your health care provider.

 

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much mefloquine?

If you or someone else has used too much mefloquine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of mefloquine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.

If you vomit a dose of mefloquine, contact your health care provider. They can tell you whether or not you should take another dose.

It is important to complete your prescribed course of mefloquine.