Postmarketing surveillance indicates that the same kind of adverse reactions are reported during prophylaxis, as well as acute treatment. Because these adverse reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to mefloquine exposure.
The most frequently reported adverse reactions are nausea, vomiting, loose stools or diarrhea, abdominal pain, dizziness or vertigo, loss of balance, and neuropsychiatric events such as headache, somnolence, and sleep disorders (insomnia, abnormal dreams). These adverse reactions may occur early in the course of mefloquine use. It has been reported that dizziness or vertigo, tinnitus and hearing impairment, and loss of balance may continue for months or years after discontinuation of the drug and may be permanent in some cases.
More severe neuropsychiatric disorders have been reported such as: sensory and motor neuropathies (including paresthesia, tremor and ataxia), convulsions, agitation or restlessness, anxiety, depression, mood swings, panic attacks, memory impairment, confusion, hallucinations, aggression, psychotic or paranoid reactions and encephalopathy. Cases of suicidal ideation and suicide have been reported.
Other less frequently reported adverse reactions include:
Cardiovascular Disorders
circulatory disturbances (hypotension, hypertension, flushing, syncope), chest pain, tachycardia or palpitation, bradycardia, irregular heart rate, extrasystoles, A-V block, and other transient cardiac conduction alterations.
Skin Disorders
rash, exanthema, erythema, urticaria, pruritus, edema, hair loss, erythema multiforme, and Stevens-Johnson syndrome.
Musculoskeletal Disorders
muscle weakness, muscle cramps, myalgia, and arthralgia.
Respiratory Disorders
dyspnea, pneumonitis of possible allergic etiology
Hepatobiliary Disorders
drug-related hepatic disorders from asymptomatic transient transaminase elevations to hepatic failure
Blood and Lymphatic System Disorders
agranulocytosis, aplastic anemia
Ocular Disorders
visual impairment, vision blurred, cataracts, retinal disorders, optic neuropathy
Other Symptoms
asthenia, malaise, fatigue, fever, hyperhidrosis, chills, dyspepsia and loss of appetite.