Mefloquine Side Effects

Not all side effects for mefloquine may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to mefloquine: oral tablet

In addition to its needed effects, some unwanted effects may be caused by mefloquine. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking mefloquine:

  • Aching joints and muscles
  • anxiety
  • blistering, loosening, peeling, or redness of the skin
  • chest pain or discomfort
  • chills
  • confusion
  • convulsions (seizures)
  • cough or hoarseness
  • dizziness
  • fainting
  • fever
  • hallucinations (seeing, hearing, or feeling things that are not there)
  • irregular, pounding, slow, or fast heartbeat or pulse
  • irritability
  • lightheadedness
  • lower back or side pain
  • mental depression
  • painful or difficult urination
  • pinpoint red spots on the skin
  • red or irritated eye
  • restlessness
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips
  • stiff neck
  • swelling of the ankles, feet, or lower legs
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • vomiting
Incidence not known
  • Blurred or loss of vision
  • continuing ringing or buzzing or other unexplained noise in the ears
  • disturbed color perception
  • double vision
  • feeling of constant movement of self or surroundings
  • halos around lights
  • hearing loss
  • hearing problems
  • loss of balance
  • loss of bladder control
  • muscle spasm or jerking of all extremities
  • night blindness
  • overbright appearance of lights
  • sensation of spinning
  • severe or continuing headache
  • sudden loss of consciousness
  • trouble sleeping
  • troubled breathing
  • tunnel vision

Some of the side effects that can occur with mefloquine may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Diarrhea
  • emotional problems
  • nausea
  • stomach pain
Less common
  • Abnormal dreams
  • loss of appetite
  • skin rash
  • Loss of hair
Incidence not known
  • Acid or sour stomach
  • belching
  • flushing or redness of the skin
  • heartburn
  • indigestion
  • skin rash with a general disease
  • stomach discomfort, upset, or pain
  • swelling
  • unusually warm skin

For Healthcare Professionals

Applies to mefloquine: oral tablet


At the doses used for treatment of acute malaria infections, the side effects possibly associated with mefloquine cannot be distinguished from the side effects usually associated with the disease. The most common side effects reported during treatment included dizziness, myalgia, nausea, fever, headache, vomiting, chills, diarrhea, skin rash, abdominal pain, fatigue, loss of appetite, and tinnitus.

The most common side effects reported during malaria prophylaxis included vomiting (3%).

Due to the long half-life of mefloquine, side effects may occur and persist up to several weeks after drug discontinuation.


Psychiatric side effects have included emotional problems and transient emotional disturbances. Behavioral changes, strange or vivid dreams, mania, nightmares, delusions, tension, anger, organic psychosis, and dysphoria have been reported. Sleep disorders (abnormal dreams), anxiety, depression, mood swings, panic attacks, aggression, psychotic or paranoid reactions, suicidal ideation, and suicide have been reported during postmarketing experience.


Gastrointestinal side effects have included vomiting, nausea, diarrhea, abdominal pain, and loss of appetite. Mouth ulcers and anorexia have been reported. Nausea, vomiting, abdominal pain, loose stools or diarrhea, dyspepsia, and loss of appetite have been reported during postmarketing experience.

Nervous system

Nervous system side effects have included dizziness, syncope, headache, tinnitus, and seizures. Encephalopathy of unknown etiology was reported during prophylactic mefloquine administration; however, the relationship to drug administration could not be established. Weakness and myoclonus have been reported. Dizziness or vertigo, headache, loss of balance, somnolence, sleep disorders (insomnia), sensory and motor neuropathies (including paresthesia, tremor, ataxia), convulsions, agitation or restlessness, memory impairment, confusion, hallucinations, and encephalopathy, and vestibular disorders (including tinnitus and hearing impairment) have been reported during postmarketing experience.


Cardiovascular side effects have included extrasystoles and bradycardia. Cardiopulmonary arrest was reported in one patient after a single prophylactic dose while concomitantly using propranolol. Transitory and clinically silent electrocardiograph alterations (including sinus bradycardia, sinus arrhythmia, first degree atrioventricular block, prolongation of the QTc interval, and abnormal T waves) and atrial flutter have been reported. Circulatory disturbances (hypotension, hypertension, flushing, syncope), chest pain, tachycardia or palpitation, bradycardia, irregular heart rate, extrasystoles, atrioventricular block, and other transient cardiac conduction alterations have been reported during postmarketing experience.


A 56-year-old male experienced thrombotic thrombocytopenic purpura (TTP) coincident with mefloquine therapy. One week before admission, the patient developed weakness, followed some days later by anorexia, myalgia, and lethargy, and, finally, by fever, confusion, and blurred vision. A central venous catheter was placed in the right jugular vein and two plasmapheresis sessions (12 units of fresh frozen plasma) were conducted in the first 24 hours. Neurological status improved after the first plasmapheresis; hematological abnormalities disappeared in the first few days of therapy. For this patient, the presence of severe neurological symptoms together with fever, thrombocytopenia, and microangiopathic anemia suggested a more complex hematological abnormality, such as TTP. The causal relation between drug and disease is supported by the temporal relation of drug intake with the onset of the clinical symptoms and laboratory abnormalities, as well as by their prompt improvement after the aphaeretic therapy and drug withdrawal.

Hematologic side effects have included decreased hematocrit, leukopenia, leukocytosis, and thrombocytopenia. Anemia, at least 8 cases of isolated thrombocytopenia, at least five cases of hemolytic anemia, and at least one case of thrombotic thrombocytopenic purpura have been reported. Agranulocytosis and aplastic anemia have been reported during postmarketing experience.


Dermatologic side effects have included skin rash, hair loss, pruritus, and telogen effluvium. Itching and cutaneous vasculitis have been reported. Rash, exanthema, erythema, urticaria, pruritus, hair loss, hyperhidrosis, erythema multiforme, and Stevens-Johnson syndrome have been reported during postmarketing experience.


Other side effects have included asthenia, fatigue, fever, and chills. Asthenia, edema, malaise, fatigue, fever, and chills have also been reported during postmarketing experience.


Musculoskeletal side effects have included myalgia. Moderately severe arthralgias and myalgias have been reported. Muscle weakness, muscle cramps, myalgia, and arthralgia have been reported during postmarketing experience.


Hypersensitivity side effects have included hypersensitivity reactions ranging from mild cutaneous events to anaphylaxis.


Respiratory side effects have included dyspnea and pneumonitis of possible allergic etiology during postmarketing experience. At least one case of eosinophilic pneumonia has been reported.

A 67-year-old female with a history of pityriasis versicolor experienced eosinophilic pneumonia coincident with infliximab therapy. She was admitted because she had experienced high-grade fever (39 degrees Celsius), malaise, productive cough, and dyspnea on exertion during the previous week. She had traveled to South Africa for 8 weeks and had taken oral mefloquine 250 mg once every week as malaria prophylaxis. The therapy was continued for 4 weeks after she returned home. A thorough workup led to the diagnosis of eosinophilic pneumonia due to the mefloquine therapy. Her condition improved after the drug was withdrawn.


Hepatic side effects have included transient elevation of transaminases. Drug-related hepatic disorders from asymptomatic transient transaminase elevations to hepatic failure have been reported during postmarketing experience.


Ocular side effects have included visual disturbances during postmarketing experience.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.