Quinine

Malaria Treatment

Quinine is primarily used to treat uncomplicated malaria caused by the parasite Plasmodium falciparum. This is a serious and potentially fatal disease transmitted to humans through the bite of an infected mosquito. Quinine works by interfering with the growth of the parasites inside the red blood cells.

Healthcare providers typically prescribe quinine when the malaria infection is known or suspected to be resistant to other common antimalarial drugs, such as chloroquine.

Important Limitations

It is important to understand the specific situations where quinine should not be used:

• Malaria Prevention: Quinine is used only to treat active infections. It is not used to prevent malaria (prophylaxis) before or during travel to high-risk areas.
• Leg Cramps: Although it was used for this purpose in the past, quinine is no longer approved or recommended for the treatment or prevention of nighttime leg cramps. Using the drug for this purpose can cause severe and potentially life-threatening medical issues.
• Severe Malaria: Quinine is generally reserved for uncomplicated cases. Severe or complicated malaria usually requires different medications or intravenous treatment.

How Quinine Works

Quinine is an antimalarial medication used to treat infections caused by Plasmodium falciparum parasites. While its exact mechanism of action is not completely understood, it is known to target the parasites during a specific part of their life cycle.

Action Against Parasites

Quinine works by attacking the parasites while they are inside the red blood cells. It is believed to interfere with the parasite's ability to grow and reproduce in the following ways:

• Nutrient Processing: It may block the parasite's ability to break down and use hemoglobin, which is the protein in red blood cells that carries oxygen.
• DNA Interference: It may interfere with the parasite's ability to replicate its genetic material (DNA), which prevents the infection from spreading further in the blood.

Scope of Activity

Quinine is effective at killing the active, asexual forms of the parasite found in the bloodstream. However, it does not typically kill the parasites when they are in other stages of development, such as when they are dormant in the liver or in the stages that allow the infection to be passed back to mosquitoes.

Common Side Effects

Many people taking quinine experience mild to moderate side effects. These may include:

• Nausea, vomiting, or stomach pain
• Diarrhea
• Headache
• Dizziness or lightheadedness
• Flushing or unusual sweating

Cinchonism

Quinine can cause a cluster of symptoms known as cinchonism. Contact your doctor if you experience:

• Ringing in the ears (tinnitus)
• Blurred vision or changes in how you see colors
• Hearing loss

Serious Side Effects

Some side effects can be severe and require immediate medical attention. Seek help right away for:

• Bleeding or bruising: Unusual nosebleeds, bleeding gums, or small purple or red spots on the skin.
• Kidney issues: Dark-colored urine, bloody urine, or a significant change in the amount of urine produced.
• Heart rhythm changes: Fast, pounding, or irregular heartbeat, or feeling like you might faint.
• Allergic reactions: Severe skin rash, hives, swelling of the face, lips, or tongue, or difficulty breathing.
• Low blood sugar: Symptoms such as sudden sweating, shaking, confusion, or extreme hunger.
• Vision loss: Sudden or severe changes in eyesight.

Boxed Warning: Serious Blood Disorders

Quinine can cause a serious condition called thrombocytopenia, which is a low level of platelets in the blood. This condition can lead to severe, permanent, or fatal bleeding. Symptoms may include unusual bruising, nosebleeds, bleeding gums, or purple spots on the skin. Quinine should be stopped immediately if these symptoms occur.

Unapproved Use for Leg Cramps

The FDA has not approved quinine for the treatment or prevention of nocturnal leg cramps. Using quinine for this purpose is considered unsafe because the risks of serious side effects, including heart rhythm problems and blood disorders, outweigh any potential benefits for leg cramps.

Contraindications

Quinine is not recommended for individuals with certain medical conditions, including:

• A history of thrombocytopenia or other blood disorders caused by quinine, mefloquine, or quinidine.
• Glucose-6-phosphate dehydrogenase (G6PD) deficiency, which can cause red blood cells to break down.
• Myasthenia gravis, as quinine may worsen muscle weakness.
• Optic neuritis (inflammation of the optic nerve).

Heart Rhythm and Vision Risks

Quinine may cause a serious heart rhythm problem known as QT prolongation, which can lead to fainting or life-threatening heartbeats. This risk is higher when taken with certain other medications. Additionally, high doses or prolonged use can cause cinchonism, a cluster of symptoms including ringing in the ears, hearing loss, headache, nausea, and blurred vision.

Blood Sugar Levels

Quinine can cause severe hypoglycemia (low blood sugar), particularly in pregnant women or individuals with certain types of malaria. Monitoring of blood glucose levels may be necessary during treatment.

Pregnancy

Quinine can cross the placenta and may cause harm to a developing fetus. Research indicates that high doses of quinine have been associated with an increased risk of miscarriage, stillbirth, and congenital malformations. However, because malaria is a life-threatening condition for both the mother and the fetus, healthcare providers may prescribe quinine if other treatment options are not available or appropriate.

Breastfeeding

Quinine is excreted into breast milk in small concentrations. While the amount transferred is generally low, caution is advised for nursing mothers. There is a specific risk for infants with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as exposure to quinine could potentially lead to hemolytic anemia in these babies.

It is important to inform a healthcare provider if you are pregnant, planning to become pregnant, or breastfeeding before starting treatment with quinine. They can help determine the safest course of action based on individual health needs and the severity of the infection.

Dosage Forms

Quinine is available in the following form for oral administration:

• Capsule: This medication is taken by mouth, typically with food to help reduce stomach irritation.

Strengths

The standard strength for quinine sulfate capsules is:

• 324 milligrams (mg)

It is essential to take this medication exactly as prescribed by a healthcare provider. Patients should only use quinine that has been legally manufactured and prescribed for them, as unapproved versions of the drug may pose significant health risks.

FDA Approval and Indications

Quinine sulfate is approved by the U.S. Food and Drug Administration (FDA) specifically for the treatment of uncomplicated malaria caused by the parasite Plasmodium falciparum. It is not approved for the prevention of malaria or for the treatment of severe or complicated malaria.

Boxed Warning

The FDA has issued a boxed warning for quinine because it can cause serious and permanent health problems. The most significant risk is a severe drop in blood platelets (thrombocytopenia), which can lead to fatal bleeding or organ damage. Other serious reactions include hemolytic uremic syndrome and thrombotic thrombocytopenic purpura.

Regulatory History and Safety Communications

The FDA has issued multiple safety communications regarding the unapproved use of quinine for nocturnal leg cramps. Because the drug can cause life-threatening side effects, the FDA has determined that the risks of using quinine for leg cramps outweigh any potential benefits. In the past, the FDA took regulatory action to remove unapproved quinine products from the market to ensure that only the FDA-approved version, which includes necessary safety labeling and a Medication Guide, is available to patients.

Alcohol and Quinine Interactions

Drinking alcohol while taking quinine is generally discouraged because it can increase the severity of certain side effects. Both substances can affect the central nervous system and the digestive tract.

Potential risks of combining alcohol with quinine include:

• Increased Dizziness: Alcohol can worsen the dizziness or lightheadedness that sometimes occurs with quinine use.
• Vision Problems: Quinine may cause blurred vision or other visual disturbances, which can be intensified by alcohol consumption.
• Stomach Irritation: Both alcohol and quinine can cause nausea or stomach upset; using them together may increase gastrointestinal discomfort.

It is important to discuss your alcohol intake with a healthcare provider before starting quinine, especially if you have a history of liver problems, as both substances are processed by the liver.