Lariam (Mefloquine)

Lariam, known generically as mefloquine, is an antimalarial medicine used to prevent and treat malaria, particularly infections caused by Plasmodium falciparum and Plasmodium vivax. It disrupts the growth of malaria parasites in the red blood cells. In the UK, it may be considered in travel medicine and prescribing decisions for people travelling to malaria-endemic regions, especially where resistance to other treatments is a concern.

What Is Lariam

Lariam (mefloquine hydrochloride) is a medicine used to treat malaria. It is available as tablets. Each tablet contains 250 mg of the active ingredient and is taken by mouth. This medicine slows the growth of the parasites in the bloodstream.

In warmer regions, malaria remains a major public health threat. It is caused by a parasite transmitted to humans through the bites of infected mosquitoes. Malaria can be life-threatening, with symptoms usually appearing 10 to 15 days after a mosquito bite, although this can vary.

The parasite mainly targets red blood cells, and the symptoms often resemble flu. In severe cases, people may develop seizures or fall into a coma, which can be fatal. Jaundice, which causes yellowing of the skin, is also commonly linked to this infection. Although malaria is now rare in most developed countries, it remains common in Africa and still causes many deaths. The disease is also found in parts of South America and Asia.

The parasites that cause malaria belong to the Plasmodium genus, and five species can infect humans. Transmission happens through the saliva of female mosquitoes, which are the ones that bite for blood. Once inside the body, the parasites multiply in the liver. P. falciparum is the deadliest of the five species, while P. vivax, P. ovale, and P. malariae are generally less aggressive. A fifth species, P. knowlesi, rarely infects humans. Health authorities use a range of prevention measures in endemic regions and continue to stress the need for effective treatment. This article looks at one of the medicines used to treat malaria.

Ingredients

Lariam's main active ingredient is mefloquine hydrochloride. This drug dissolves only slightly in water. It is a white crystal with a molecular weight of 414.78 g/mol. It is chemically similar to quinine.

Each tablet also contains several inactive ingredients alongside the 250 mg of active substance. For the full list of ingredients, please read the medicine packaging.

Mefloquine is classified as a 4-quinolinemethanol derivative and works as a blood schizonticide, targeting the erythrocytic stages of the malaria parasite. Mefloquine is taken by mouth, typically as 250 mg tablets. It has a long elimination half-life of about 2 to 4 weeks, which allows for once-weekly dosing when used for prevention.

Despite its effectiveness, mefloquine is linked to a range of side effects, including neuropsychiatric reactions, which may continue even after stopping the drug. Because of these possible effects, it is contraindicated in people with a history of psychiatric disorders or seizures. Mefloquine's unique pharmacokinetic properties and mechanism of action make it an important option in malaria-endemic regions, especially where resistance to other antimalarials has developed.

Uses

Lariam is mainly used to prevent and treat malaria. It is effective against both Plasmodium falciparum and Plasmodium vivax, including strains resistant to chloroquine. While Lariam can be taken once weekly for prevention, starting one week before entering a malaria-endemic area, it is also used in acute malaria, usually as a single oral dose for treatment.

Treatment of Acute Malaria Infections

The most common treatment for malaria uses a combination of two medicines. The first is usually artemisinin. The second may be lumefantrine or mefloquine (Lariam). Quinine and doxycycline may sometimes be used instead of artemisinin. Other compounds may also be used as the second medicine.

When the first symptoms appear, you should see a doctor straight away. A blood test is needed to confirm the disease. Treatment should start only after a positive result. This helps reduce the risk of drug resistance. For example, artemisinin is ineffective in some parts of Asia because of resistance.

Lariam is used to treat acute malaria caused by mefloquine-susceptible strains of Plasmodium falciparum and P. vivax. It is generally used for uncomplicated infection. Mefloquine also has activity against P. ovale and P. malariae.

Doctors need to be especially careful with patients infected with P. vivax. While Lariam stops the parasites from growing, it does not remove them from the liver. After treatment with Lariam, a second treatment with primaquine may be useful. Another similar compound may also be used. This helps clear the parasites from the liver and reduce the risk of relapse.

Prevention of Malaria

As with many illnesses, prevention is better than treatment. Some of the most effective ways to prevent malaria are:

• in areas where malaria is common, people should avoid mosquito bites; for example, by using mosquito nets while sleeping;
• using mosquito repellent during daily activities;
• using insecticides to remove mosquitoes from homes and other buildings;
• removing standing water to stop mosquitoes breeding;
• introducing fish species that feed on mosquito larvae into ponds and lakes;
• vaccination and immunisation campaigns.

The last point is helpful for people travelling to areas where malaria is common. Some medicines are available for this purpose. Lariam offers some protection against infections caused by P. falciparum and P. vivax. It is effective against strains of P. falciparum that are resistant to chloroquine.

Children in some regions receive a combination of sulfadoxine and pyrimethamine for prevention. Women who are more than 3 months pregnant should receive the same combination. Only one malaria vaccine is available, and it reduces the risk of infection by 40%. However, pharmaceutical companies are still trying to find more effective treatments.

Dosage

In the UK, you should never deviate from the doctor's instructions for taking Lariam. Increasing or reducing the prescribed mefloquine dose can be counterproductive. Here are some general recommendations for using this medicine for prevention:

• Unless your doctor tells you otherwise, take one dose a week. Choose the same day each week for your dose, such as every Monday.
• You should start taking this medicine at least 1 week in advance for better protection. This means taking it before you enter an area where malaria is common.
• Continue taking the medicine as described above while you are in the risk area. Do not stop the weekly doses when you leave. You should keep taking them for at least one month afterwards.
• If you stop taking Lariam, use a different method of prevention.

As well as this medicine, you should also use the other prevention methods mentioned earlier in this article.

Adult Patients

The recommended dose is five Lariam tablets to treat the infection in adults. You must take them together as a dose of 1250 mg. For comfort, take the dose after your main meal. Swallow it with water. If this treatment does not give a positive result within 2 to 3 days, the doctor should use a different medicine. Likewise, a different medicine should be used to treat the infection if you were taking this medicine for prevention.

For prevention, follow the recommendations listed above. Start taking Lariam 2-3 weeks in advance if you use other medicines as well. This helps the doctor check whether any of the medicines interact.

Paediatric Patients

Doctors should not prescribe Lariam to babies under 6 months old. Only a doctor may prescribe it to treat malaria in such a case. Children weighing under 20 kg should not use this medicine as a preventive measure.

The usual infant dose is 20-25 mg per kg of body weight. This is given as a single dose. However, to reduce the risk of serious side effects, the doctor may divide the dose. The child may take two doses 6-8 hours apart. As already described, the tablet can be crushed if needed. It can then be mixed with water, milk or another drink to make it easier to take.

For malaria prevention, children must take a weekly dose. This is 5 mg per kg of body weight. As a rule of thumb, you can use the doses shown in the following table:

If there is no improvement within 2 to 3 days of treatment, a different medicine should be used. Likewise, if Lariam does not prevent malaria, a different medicine should be chosen for treatment. Children are more likely to vomit after taking this product. If this happens, follow the recommendations given earlier in this article.

You should take these tablets after your main meal. Swallow each tablet with plenty of water, about 250 ml. If it is hard to swallow, you can crush it. Mix the powder with a drink of your choice to make it easier to take.

Taking Lariam may cause vomiting. This may happen within half an hour of taking the medicine. In that case, you will need to take another dose. You should repeat only half the dose if vomiting happens between half an hour and one hour later. If Lariam continues to cause vomiting, seek medical advice.

Geriatric Patients

There is no clear agreement on using Lariam in older adults aged over 65. Some researchers found no difference compared with treatment in younger patients. However, some studies have reported heart abnormalities linked to this drug. Because of this, the doctor should carefully assess whether Lariam is suitable for an older patient.

What Is the Onset of Action for Lariam?

Lariam (mefloquine) typically begins to work within one week when used for malaria prevention, as it is recommended to start taking the medicine at least one week before entering a malaria-endemic area. For the treatment of malaria, Lariam can be effective within 24 hours after taking it. However, symptoms may take longer to improve depending on how severe the infection is and how the individual responds to the medicine. It is important to seek medical advice promptly if symptoms persist or get worse.

Important Safety Information

Long-term use of Lariam requires regular blood tests. Because of the risk of mefloquine toxicity, these tests are needed to check that your liver is in good condition. Long-term use of Lariam may also affect your vision. Consider regular eye checks with an ophthalmologist.

People with a history of depression, anxiety disorders, seizures or other mental health conditions should avoid using Lariam for malaria prevention. Additionally, in the United Kingdom, it is crucial to inform healthcare providers about any existing medical conditions, such as epilepsy or liver problems, before starting treatment.

Pregnancy and Breastfeeding

Animal studies suggest that Lariam may affect embryo development. However, similar studies have not been carried out in pregnant women. There is no evidence that Lariam affects the human fetus. In any case, there must be a strong reason to use Lariam during pregnancy. Women travelling to a risk area should avoid becoming pregnant. Ask your pharmacist about effective contraception.

Mefloquine is present in small amounts in breast milk. The drug can cause severe reactions in the baby. Because of this, the doctor must decide whether Lariam should be discontinued. The doctor must weigh the mother's benefit against the baby's risk.

Paediatric Use

Multiple clinical trials support the use of Lariam in children younger than 16 years old. In such cases, it is safe and effective at the recommended doses. Researchers have not documented its use in babies under 6 months of age. It is better to avoid using Lariam in such young infants.

Contraindications

You should not use Lariam if you have a history of mental illness. This includes anxiety, depression and schizophrenia. You should also avoid this medicine if you have had seizures. In some life-threatening cases of malaria, the doctor may still prescribe Lariam. In that case, the benefit of saving your life may outweigh the risk of Lariam-related psychosis.

Tell the doctor about any other medical conditions you have or have had. For example, let them know if you have heart or liver problems. The doctor also needs to know about conditions such as epilepsy or diabetes. Tell them if you are allergic to any medicines. Allergy to mefloquine, quinine or quinidine is especially important in this case.

Drug-Drug Interactions

Drug interactions have not been studied in detail. Because of this, tell the doctor about all other medicines you take. This includes medicines available without a prescription. You should also tell them about any vitamin supplements and herbal products you use.

The doctor will pay special attention to the following:

• medicines for heart conditions and high or low blood pressure;
• medicines for depression and other mental health conditions;
• medicines used to control seizures;
• medicines for tuberculosis;
• live vaccines.

You should also tell them about any recreational drugs you use.

Side Effects

At the recommended doses, Lariam is usually tolerated by most people. However, in some urgent situations, you may need to go to A&E straight away. For example, this may happen if you have an allergic reaction to the medicine. Signs of an allergic reaction include swelling of the face or other parts of the body. Breathing problems and hives can also be signs of an allergic reaction.

Clinical

Most side effects are mild and may include dizziness, vomiting, diarrhoea and flu-like symptoms. These symptoms do not usually need special medical attention. It can be hard to tell these effects apart from the symptoms of malaria.

Psychiatric or Nervous System Problems

Lariam may affect the nervous system. The patient may experience mental health problems and other unwanted effects. These are long-term side effects of mefloquine. These psychiatric problems may continue for a long time. Even if the patient stops taking the medicine, the problems may remain. In some extreme cases, they may last for years or become permanent.

Tell the doctor about your full medical history. With this information, the doctor can assess whether Lariam is appropriate for you. The doctor will try to keep the risk of these long-term side effects as low as possible. Stop taking Lariam straight away if you experience any of the following:

• headache;
• tinnitus;
• dizziness or difficulty keeping your balance;
• lack of coordination;
• changes in mental state, such as depression or suicidal thoughts.

Seek medical advice if you experience any of the effects listed above.

Post-Marketing

Most side effects in this category include vertigo, dizziness and loss of balance. Other reported problems are:

• sleep disorders (nightmares, insomnia);
• cardiovascular disorders (high or low blood pressure, arrhythmias);
• skin disorders (rash, pruritus);
• muscular disorders (weakness, cramps);
• respiratory disorders.

Other effects have also been reported. Not all of them are listed above. People have also reported visual problems, fatigue, malaise and other symptoms. This is in addition to the psychiatric and nervous system problems mentioned earlier in this article.

Overdose

You may have symptoms of poisoning. If this happens, seek emergency medical attention. In the UK, for example, you can call 999.

Most commonly, you may have breathing problems after an overdose. You may pass out. Do not waste time and seek emergency medical attention.

Missed Dose

Missing a dose is usually not a major problem in treatment cases. You generally take a single dose of Lariam. So take the dose when you realise you missed it.

If you miss a dose of Lariam during prevention, take it as soon as you can. Then take the next dose as scheduled. However, if you miss the dose within a week before entering a risk area, contact the doctor. You will need a different prevention method.

Comparison of Lariam with Other Antimalarials

Here is a comparison of Lariam with other common antimalarials:

Lariam is often chosen for its weekly dosing schedule, which may be more convenient for some travellers. However, it is associated with more severe side effects than alternatives such as Malarone and doxycycline. Malarone offers rapid protection and milder side effects, but at a higher cost. Doxycycline is effective and affordable, but requires daily dosing, which some people may find difficult. Chloroquine is no longer recommended in many malaria-endemic areas because of resistance.

Lariam and Hydroxychloroquine: Key Differences and Uses

Lariam (mefloquine) and hydroxychloroquine are both medicines used to treat and prevent malaria, but they differ in their mechanisms, indications and side effects.

Lariam (Mefloquine)

Uses:

• Lariam is indicated for the treatment of mild to moderate acute malaria caused by mefloquine-susceptible strains of P. falciparum and P. vivax. It is particularly useful against chloroquine-resistant strains.
• It is also used for prophylaxis against malaria in travellers to areas where chloroquine-resistant strains are common.

Mechanism of Action:
Mefloquine works by interfering with the parasite's ability to digest haemoglobin, leading to its death. It is effective against both chloroquine-sensitive and resistant strains of malaria.

Side Effects:
Common side effects include dizziness, nausea, vomiting and sleep disturbances. Serious side effects can include neuropsychiatric symptoms such as anxiety or depression, which may occur because of its effects on the central nervous system.

Hydroxychloroquine

Uses:

• Hydroxychloroquine is primarily used for the treatment of uncomplicated malaria caused by certain strains of Plasmodium (e.g., P. falciparum, P. malariae, P. ovale, and P. vivax) in areas where chloroquine resistance is not reported.
• It is also widely prescribed for autoimmune conditions such as rheumatoid arthritis and systemic lupus erythematosus, acting as a disease-modifying antirheumatic drug (DMARD).
• Additionally, hydroxychloroquine may be used for conditions such as discoid lupus erythematosus and porphyria cutanea tarda.

Mechanism of Action:
Hydroxychloroquine works by modulating the immune response and increasing lysosomal pH, which helps inhibit the growth of malaria parasites. It also has anti-inflammatory properties that are beneficial in autoimmune disorders.

Side Effects:
Common side effects include nausea, vomiting, headache and blurred vision. Serious side effects can include retinopathy, skin reactions (such as Stevens-Johnson syndrome), blood disorders and liver damage.

Comparison Table

Storage

Store your Lariam tablets in a dry place. The temperature can be between 15°C and 30°C, although ideally it should be 25°C. Keep your tablets out of the reach of children.

Brand names of mefloquine in different countries