Cinchonism

Excerpt

Cinchonism is a collection of symptoms stemming from the ingestion of quinoline derivatives and their subsequent neural, retinal, and auditory toxicity. Ingestion of quinoline derivatives can produce a multitude of detrimental effects. Cinchonism is a subset of these effects initially believed to be primarily neurally mediated. This definition does not include the pro-arrhythmic properties of these drugs. It is commonly described as tinnitus, reversible hearing loss, flushing, confusion, diarrhea, and visual disturbances, including permanent blindness in some cases. In addition, some literature includes ataxia, tremor, and dystonic reactions as a part of cinchonism.

The word cinchonism comes from the Cinchona tree, which is the source of quinine. Cinchona was the second countess of Chinchon in Peru. The people of Peru used the bark of the Cinchona to prevent shivering by mixing ground bark with sweetened water, producing a tonic solution. The Jesuits primarily brought Cinchona to Europe, using it to manage malaria in Rome, which was the first effective therapy available against Plasmodium falciparum when other drugs, such as chloroquine, emerged.

The recent pandemic of COVID-19 has led to hydroxychloroquine, another quinine derivative that can present with cinchonism. Adverse effects have been associated with drug dosage. Auditory manifestations following hydroxychloroquine can either be temporary or permanent; however, ototoxicity associated with using chloroquine has been observed to be irreversible.

Quinoline derivatives are used for many reasons, including as a class 1A antiarrhythmic (quinidine), an anti-malarial agent, and certain viral infections, including SARS-CoV-2, for a period of time. This article further elucidates the full spectrum of cinchonism.

Quinine has direct toxic effects on the inner retina. While the natural course is of some improvement over days to weeks, residual deficit and visual field constriction are common, and the vision may never improve.