Quinine can adversely affect almost every body system. The most common adverse events associated with quinine use are a cluster of symptoms called “cinchonism”, which occurs to some degree in almost all patients taking quinine.¹

Symptoms of mild cinchonism include:

• Headache
• Vasodilation
• Sweating
• Nausea
• Tinnitus
• Hearing impairment
• Vertigo or dizziness
• Blurred vision
• Disturbance in color perception.¹

More severe symptoms of cinchonism are:

• Vomiting
• Diarrhea
• Abdominal pain
• Deafness
• Blindness
• Disturbances in cardiac rhythm or conduction.¹

Most symptoms of cinchonism are reversible and resolve with discontinuation of quinine. Cinchonism occurs in virtually all patients with quinine overdose.¹ Mild symptoms (tinnitus, headache, nausea, and slight visual disturbances) usually resolve promptly, but severe symptoms can persist for months.² Gastrointestinal symptoms, tinnitus, and vertigo are prominent symptoms of cinchonism, but visual impairments are often the most dramatic and the most upsetting for the patient.³

Overdosage¹

Quinine overdose can be associated with serious complications, including visual impairment, hypoglycemia, cardiac arrhythmias, and death. Visual impairment can range from blurred vision and defective color perception, to visual field constriction and permanent blindness. Cinchonism occurs in virtually all patients with quinine overdose. Symptoms range from headache, nausea, vomiting, abdominal pain, diarrhea, tinnitus, vertigo, hearing impairment, sweating, flushing, and blurred vision, to deafness, blindness, serious cardiac arrhythmias, hypotension, and circulatory collapse. Central nervous system toxicity (drowsiness, disturbances of consciousness, ataxia, convulsions, respiratory depression and coma) has also been reported with quinine overdose, as well as pulmonary edema and adult respiratory distress syndrome.

Most toxic reactions are dose-related; however some reactions may be idiosyncratic because of the variable sensitivity of patients to the toxic effects of quinine. A lethal dose of quinine has not been clearly defined, but fatalities have been reported after the ingestion of 2 to 8 grams in adults.

Quinine, like quinidine, has Class I antiarrhythmic properties. The cardiotoxicity of quinine is due to its negative inotropic action, and to its effect on cardiac conduction, resulting in decreased rates of depolarization and conduction, and increased action potential and effective refractory period. ECG changes observed with quinine overdose include sinus tachycardia, PR prolongation, T wave inversion, bundle branch block, an increased QT interval, and a widening of the QRS complex. Quinine’s alpha-blocking properties may result in hypotension and further exacerbate myocardial depression by decreasing coronary perfusion. Quinine overdose has been also associated with hypotension, cardiogenic shock, and circulatory collapse, ventricular arrhythmias, including ventricular tachycardia, ventricular fibrillation, idioventricular rhythm, and torsades de pointes, as well as bradycardia, and atrioventricular block.

Quinine is rapidly absorbed, and attempts to remove residual quinine sulfate from the stomach by gastric lavage may not be effective. Multiple-dose activated charcoal has been shown to decrease plasma quinine concentrations.

Forced acid diuresis, hemodialysis, charcoal column hemoperfusion, and plasma exchange were not found to be effective in significantly increasing quinine elimination in a series of 16 patients.

1 Quinine sulfate [package insert]. Philadelphia, PA: Mutual Pharmaceutical Co.; 2006. Available at: http://thomsonweb.esourcegroup.com/files/PI_0.pdf.

2 Pughe K. Quinine. ICPS Intox Databank, UK National Poisons Information Service (Newcastle Centre). Available at: http://www.intox.org/databank/documents/pharm/quinine/ukpid13.htm. Accessed June 6, 2006.

3 Dyson EH, Proudfoot AT, Prescott LF, et al. Death and blindness due to overdose of quinine. Br Med J. 1985;291:31-33.