Though quinine has been used therapeutically since the 17th century, it has not lost favor as one of the first-line treatments for malaria. Quinine works by binding to the DNA of the malaria parasite, preventing its replication. With the infection controlled, the body can heal. Quinine is most effective in uncomplicated malaria cases where the type of parasite is unknown. It is also used in pregnant women because it has a low risk for birth defects relative to other anti-malarial drugs. As with most drugs, some patients who use quinine may experience adverse effects.
Cinchonism
Quinine has a unique side effect profile because it causes a cluster of symptoms known as "cinchonism." The prescribing information for quinine states that almost everyone who takes the medication experiences some degree of cinchonism. Milder forms of the syndrome include vasodilation or widening of blood vessels as well as headache, sweating, nausea, ringing in the ears, hearing impairment, vertigo or dizziness, blurred vision and disturbance in color perception. On the more severe side, patients can experience vomiting, diarrhea, abdominal pain, deafness, blindness and disturbances in cardiac rhythm. Most symptoms of cinchonism are reversible and resolve when people stop taking quinine.
Thrombocytopenia
Thrombocytopenia is an all-inclusive term for any disorder in which the body does not have enough platelets. Platelets are essential for the blood's ability to clot, so a reduced number could lead to bleeding problems and could potentially be life-threatening. Thrombocytopenia could be the result of any of a number of different quinine-induced disorders such as thrombotic thrombocytopenic purpura, hemolytic uremic syndrome, immune thrombocytopenic purpura, blackwater fever and disseminated intravascular coagulation. The patient should be aware of any signs of easy bruising, small pinpoint red spots on the skin or increased bleeding when brushing the teeth. Thrombocytopenia usually resolves within a week after discontinuing quinine, but if taken again, a person could experience a more severe and almost instantaneous reaction due to antibody formation.
Hypoglycemia
Quinine can overstimulate the pancreas, causing it to release more insulin than normal. When this happens, the patient can experience hypoglycemia, or low blood sugar. Hypoglycemia is more likely to occur in women who are taking quinine while pregnant. Some symptoms of hypoglycemia can include sweating, weakness, nausea, vomiting or confusion. If a person experiences symptoms of low blood sugar, the patient medication guide recommends drinking fruit juice or eating a snack. A physician should be called for further instruction.
Hypersensitivity Reactions
Other serious hypersensitivity reactions have been reported with quinine as well, including difficulty breathing, throat and facial swelling, itching, bronchospasms and hives. Quinine can also cause serious skin rashes in some patients, including Stevens-Johnson syndrome and toxic epidermal necrolysis. Both syndromes are characterized by reddening and blistering of the skin, though toxic epidermal necrolysis is more widespread across the body. Any symptom of a hypersensitivity reaction should be viewed as life-threatening, and a person should immediately contact the prescriber.
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