Qualaquin can cause serious side effects on your heart, kidneys, or blood cells. Stop taking  Qualaquin and call your doctor at once if you have headache with chest pain and severe dizziness, fast or pounding heartbeats, unusual bruising or bleeding (nosebleeds, bleeding gums, purple or red spots under your skin), signs of infection (fever, chills, mouth sores), severe lower back pain, or blood in your urine.
You should not take Qualaquin if you have a heart rhythm disorder called Long QT syndrome, a genetic enzyme deficiency called glucose-6-phosphate dehydrogenase deficiency (G-6-PD), myasthenia gravis, optic neuritis (inflammation of the nerves in your eyes), if you have taken this medicine in the past and it caused a blood cell disorder or severe bleeding.
Some people have used Qualaquin to treat leg cramps, but this is not an FDA-approved use. Using this medication improperly or without the advice of a doctor can result in serious side effects or death.
Before taking this medicine
You should not use this medication if you have ever had an allergic reaction to Qualaquin or similar medicines such as mefloquine or quinidine, or if you have:
a heart rhythm disorder called Long QT syndrome;
an enzyme deficiency called glucose-6-phosphate dehydrogenase deficiency (G-6-PD);
myasthenia gravis;
optic neuritis (inflammation of the optic nerve); or
if you have taken Qualaquin in the past and it caused a blood cell disorder, severe bleeding, or kidney problems.
To make sure Qualaquin is safe for you, tell your doctor if you have:
heart disease or a heart rhythm disorder;
low levels of platelets in your blood;
low potassium levels in your blood (hypokalemia); or
liver or kidney disease.
FDA pregnancy category C. It is not known whether Qualaquin will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.
Quinine can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
Do not give this medication to a child younger than 16 years old.
