Mild headache, flushing, unusual sweating, nausea, ringing in the ears, decreased hearing, dizziness, blurred vision, and temporary changes in color vision may occur. If any of these effects persist after your treatment is finished, or if these effects worsen while taking the medication, tell your doctor or pharmacist promptly.
Quinine may cause low blood sugar (hypoglycemia), especially during pregnancy. Symptoms of low blood sugar include sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. If symptoms of low blood sugar occur, increase your blood sugar by eating a quick source of sugar such as table sugar, honey, or candy, or drink fruit juice or non-diet soda. Tell your doctor right away about the reaction and the use of this product.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if any of these rare but very serious side effects occur: easy bruising/bleeding, unusual purple/brown/red spots on the skin, signs of serious infection (such as high fever, severe chills, persistent sore throat), signs of a sudden loss of red blood cells called hemolytic anemia (such as severe tiredness, brown urine, pale lips/nails/skin, rapid breathing at rest), signs of severe liver problems (such as persistent nausea/vomiting, abdominal pain, severe weakness, yellow skin/eyes, unusually dark urine), change in the amount of urine.
Seek immediate medical attention if any of these rare but very serious side effects occur: chest pain, severe dizziness, fainting, fast/irregular heartbeat, blindness.
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.