This article describes possible side effects of quinine oral capsule. To learn more about quinine, including the drug’s uses, ways to save on cost, and more, talk with your doctor or pharmacist.
Quinine oral capsule is a generic version of the brand-name drug Qualaquin.
Boxed warning: Risk of serious hematologic reactions
Quinine oral capsule has a boxed warning for the risk of serious blood reactions. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
For details, see the “Side effects of quinine in detail” section below.
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More common side effects of quinine
Quinine oral capsule may cause mild or serious side effects. Below are some of the more common side effects of this medication.
Commonly reported side effects of quinine oral capsule include:
Mild side effects of quinine
Quinine may cause certain mild side effects. Most often, mild side effects are temporary and can be easily managed. Tell your doctor or pharmacist if you have side effects that don’t go away or become bothersome.
Mild side effects of quinine oral capsule that occurred in studies include:
- headache
- widening of blood vessels
- nausea
- tinnitus (ringing in the ears)
- hearing loss
- dizziness or vertigo
- changes in how you see colors
- vomiting
- diarrhea
- stomach pain
- fever
- chills
- sweating
- confusion
- tremors (uncontrollable shaking in a part of your body)
- loss of balance
- loss of appetite
- muscle pain or weakness
- mild allergic reaction*†
Quinine oral capsule may cause more mild side effects than those listed above. For details, see the drug’s prescribing information.
* To learn more about this side effect, see the “Side effects of quinine in detail” section below.
† An allergic reaction is possible with quinine oral capsule. But it’s unclear whether it occurred in the drug’s studies.
Serious side effects of quinine
Quinine may cause certain serious side effects. If you have any serious side effects from quinine oral capsule, call your doctor right away. But if you think you’re having a medical emergency or your side effects feel life threatening, take immediate action. Call 911 or a local emergency number, or go to the nearest emergency room.
After the FDA approves a drug, it tracks and reviews side effects of the medication. Visit MedWatch’s website if you’d like to notify the FDA about a side effect you’ve had with quinine.
Serious side effects of quinine oral capsule that occurred in studies include:
- deafness
- heart rhythm problems
- seizures
- coma
- difficulty speaking
- suicide
- serious skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis
- breathing problems
- fluid in the lungs
- chest pain
- low blood pressure
- liver problems
- low blood sugar*
- kidney problems
- vision problems, including sudden loss of vision or blindness
- risk of serious blood reaction*†
- severe allergic reaction*‡
* To learn more about this side effect, see the “Side effects of quinine in detail” section below.
† Quinine oral capsule has a boxed warning for this side effect. A boxed warning is the most serious warning from the FDA.
‡ An allergic reaction is possible with quinine oral capsule. But it’s unclear whether it occurred in the drug’s studies.
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Get free cardCommon questions about side effects of quinine
Here are answers to some common questions about side effects of quinine oral capsule. If you have other questions, talk with your doctor or pharmacist.
How long do side effects of quinine usually last?
It depends. Usually, mild side effects are temporary. And in most cases, they will go away on their own within a few days. But quinine may cause side effects that can last for a while after stopping treatment. These include blindness, hearing problems, and kidney problems.
If you have concerns about the side effects of quinine, talk with your doctor.
Does quinine cause long-term side effects?
Yes, in some cases quinine oral capsule may cause long-term side effects. These can last for a while after you’ve stopped taking the drug.
Examples of long-term side effects reported with quinine oral capsule include:
- blindness
- hearing loss
- kidney problems
Talk with your doctor to learn more about these side effects and how to manage them. Ask your doctor for more information about how long these side effects of quinine may last.
Can quinine be used for nighttime leg cramps? If so, are the side effects the same as when it’s used for malaria?
Maybe. But quinine isn’t approved by the FDA for the treatment of nighttime leg cramps.
In some cases, doctors may prescribe quinine off-label for leg cramps. With off-label use, doctors prescribe a drug for a purpose other than what it’s approved for.
If you have questions about your treatment options for leg cramps, talk with your doctor.
Side effects of quinine in detail
Below you’ll find details on some of the side effects of quinine oral capsule.
Risk of serious hematologic reactions
Quinine can cause serious hematologic (blood) reactions if it’s used for the treatment or prevention of nighttime leg cramps. This includes low blood platelet count, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. In some cases, this has led to chronic kidney disease.
With blood reactions, you may experience symptoms such as:
- unexplained bruises or bleeding
- blood in your urine
- bloody diarrhea
- tiny red or purple spots on the skin
- pale skin
- yellowing skin or eyes
- nosebleeds
- bleeding gums
Due to this risk, quinine is not approved for the treatment of nighttime leg cramps.
Ways to manage
If you experience any signs or symptoms of abnormal bleeding, tell your doctor. They’ll likely recommend treatment for your symptoms and have you stop taking quinine.
Heart rhythm problems
In studies, heart rhythm problems, such as QT prolongation, occurred in people taking quinine oral capsule. This side effect may be serious.
With QT prolongation, you may not experience any symptoms. But if symptoms are present, they can include:
- dizziness
- heart palpitations (feeling of skipped or extra heartbeats)
- fainting
- seizures
Certain factors can increase the risk of heart rhythm problems with quinine oral capsule. These include:
- history of structural heart disease
- irregularities in your heart’s conduction system
- sick sinus syndrome in older adults
- certain types of atrial fibrillation (AFib)
- history of myocardial ischemia (a condition where there’s inadequate blood flow to the heart)
- taking medications that affect your heart rhythm
Ways to manage
If you have concerns about heart rhythm problems, tell your doctor. They can discuss the risks and benefits of quinine oral capsule and talk with you about alternative treatments for your condition.
Low blood sugar
Hypoglycemia (low blood sugar) occurred in studies of people taking quinine oral capsule. This side effect may be serious.
Quinine promotes the release of insulin from the pancreas. Insulin is a hormone that moves glucose (sugar) from the blood into the liver. This lowers your blood sugar levels and can lead to hypoglycemia.
Symptoms of low blood sugar include:
- sweating
- paleness
- hunger
- fatigue (low energy)
- irritability
- fast heart rate
- difficulty concentrating
The risk of low blood sugar from taking quinine is especially high in pregnant females.*
* Sex and gender exist on spectrums. In this article, we use the term “female” to refer to a person’s sex assigned at birth.
Ways to manage
It’s important to tell your doctor if you experience symptoms of hypoglycemia. They’ll determine the cause, offer treatment options, and decide if you should stop taking quinine.
Allergic reaction
For some people, quinine oral capsule can cause an allergic reaction. But it’s not clear whether this side effect occurred in the drug’s studies.
Symptoms can be mild or serious, and they may include:
- itchiness
- skin rash
- swelling under the skin, typically affecting eyelids, lips, hands, or feet
- swelling of the mouth, tongue, or throat, which can make it hard to breathe
- flushing (temporary warmth, redness, or deepening of skin color)
Ways to manage
For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.
For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to quinine oral capsule, your doctor may recommend taking a different medication instead.
Warnings for quinine
Below are some factors you may want to discuss with your doctor before taking quinine oral capsule.
Boxed warning: Risk of serious hematologic reactions
Quinine has a boxed warning for the risk of serious hematologic reactions. A boxed warning is the most serious warning from the FDA.
For details, see the “Side effects of quinine in detail” section above.
Other warnings
It may not be safe for you to take quinine oral capsule if you have specific health conditions. These are sometimes called drug-condition interactions. Other things may also affect whether quinine oral capsule is a safe treatment option for you.
Before taking quinine oral capsule, tell your doctor about your health and medications you take. Things to consider include:
- history of heart, kidney, or liver problems
- if you are currently pregnant or breastfeeding
- past allergic reaction to quinine
- taking medications that may affect your heart rhythm
Quinine and pregnancy
It’s not known whether quinine oral capsule should be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.
Quinine and breastfeeding
It’s not known whether quinine oral capsule should be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication.
Quinine and alcohol
Quinine oral capsule isn’t known to interact with alcohol.
But your doctor may still recommend avoiding or limiting alcohol while taking quinine oral capsule. On their own, alcohol and quinine can both cause liver problems. If they’re taken together, the risk of serious liver problems can increase.
If you drink alcohol, talk with your doctor about whether it’s safe to consume it during your treatment with quinine oral capsule.
What to ask your doctor
This article describes common and serious side effects of quinine oral capsule. If your doctor prescribes this medication, they can discuss possible side effects with you. Let your doctor know if you have concerns or questions about treatment with this medication.
Here’s a list of some possible questions you may want to ask your doctor:
- Does my risk of vision problems increase the longer I take quinine oral capsule?
- Are there other treatments for malaria that cause fewer side effects?
- Does my medical history put me at higher risk of side effects than others?
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.