Lariam Side Effects Onset, Duration & Management
What to expect when taking Lariam (mefloquine), from common dizziness to rare severe reactions. Learn more about malaria prevention.
Key Takeaways
- Most common: Dizziness (25%), insomnia (20%), vivid dreams (15%)
- Onset: Neuropsychiatric effects may start within 1-3 doses; GI issues within hours
- Duration: Most resolve after stopping, but dizziness/depression can persist for months
- Emergency effects: Suicidal thoughts, hallucinations, severe heart rhythm changes
- High-risk groups: History of depression, seizures, or cardiac conditions
Understanding Lariam side effects is crucial for safe malaria prevention. This guide covers when they start, how long they last, and when to seek medical help.
Common Side Effects of Lariam
Mild Effects (≥1 in 10)
- Dizziness, vertigo
- Insomnia, vivid dreams
- Nausea, diarrhea
- Headache
Moderate Effects (1 in 100)
- Anxiety, mood swings
- Balance problems
- Visual disturbances
- Rash, itching
Note: Side effects are more likely with higher doses (treatment) and long-term use (>6 months).
When Do Lariam Side Effects Start?
| Side Effect | Typical Onset | Peak Timing |
|---|---|---|
| Gastrointestinal (nausea, diarrhea) | 2-6 hours | First 48 hours |
| Dizziness/vertigo | 1-3 doses | First 2 weeks |
| Neuropsychiatric (anxiety, dreams) | 1-3 doses | First month |
| Cardiac (palpitations) | Within 24 hours | First 72 hours |
How Long Do Side Effects Last?
| Side Effect | Duration After Stopping | Notes |
|---|---|---|
| Gastrointestinal | 2-3 days | Resolves quickly |
| Dizziness/balance issues | Weeks to months | Due to long half-life (2-4 weeks) |
| Neuropsychiatric | Months (rarely years) | Requires medical evaluation |
| Skin reactions | 1-2 weeks | May need treatment |
Long-term effects: 5% of users report persistent dizziness or depression >6 months post-treatment.
Serious Side Effects (Require Immediate Action)
Stop Lariam and Seek Emergency Help If:
- Suicidal thoughts or self-harm urges
- Hallucinations or paranoia
- Severe chest pain or irregular heartbeat
- Seizures or loss of consciousness
- Severe skin blistering (Stevens-Johnson syndrome)
Report to Your Doctor
- New or worsening depression/anxiety
- Persistent vomiting preventing dose retention
- Vision/hearing changes
- Unexplained bruising/bleeding (blood disorder sign)
Managing Side Effects
Prevention Strategies
- Test dose: Start 10 days pre-travel to identify intolerable reactions
- Evening dosing: Take with dinner to sleep through dizziness
- Avoid triggers: No alcohol, caffeine, or other CNS depressants
- Hydration: Reduce GI upset with plenty of water
Symptom Relief
| Side Effect | Management |
|---|---|
| Dizziness | Rise slowly; avoid driving |
| Insomnia | Good sleep hygiene; melatonin if needed |
| Nausea | Ginger capsules; small frequent meals |
| Anxiety | Breathing exercises; consider alternative prophylaxis |
Frequently Asked Questions
Why does Lariam cause neuropsychiatric effects?
Mefloquine crosses the blood-brain barrier, disrupting neurotransmitters like serotonin and dopamine in susceptible individuals.
Can I drink alcohol with Lariam?
Avoid alcohol—it worsens dizziness and may increase psychiatric side effects.
Are side effects worse with treatment doses?
Yes. High treatment doses (15-25mg/kg) have 3x higher side effect rates than weekly prevention doses.
How can I tell if my dreams are abnormal?
Seek help if dreams cause sleep avoidance, daytime distress, or violent content.
Is there a test to predict side effects?
No. A 10-day pre-travel trial is the best indicator. Genetic testing for psychiatric risk is experimental.
Need Treatment for malaria
If you're experiencing symptoms of a bacterial infection, our UK-registered doctors can help determine if Lariam Tablets is appropriate for your condition through a confidential online consultation.
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Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 03 November 2025
Next Review: 05 May 2026
Published on: 03 November 2025
Last Updated: 04 November 2025
