Barking Up the Wrong Tree (Cinohonism, Quinine & Quinidine)

Author: Clinical Toxicology LLC
Published: Wed 16 Dec 2020
Episode Link: https://thepoisonlab.com/episode/barking-up-the-wrong-tree-cinohonism-quinine-quinidine

In this episode Ryan and Toxo discuss some potential toxic spices and break down the toxicity and treatment of a once well known medicine

Definition: Classic toxicities caused by ingestion of quinoline derivatives from cinchona bark.
Brief Review:
https://pubmed.ncbi.nlm.nih.gov/32644745/

Sources:
Powdered cinchona bark: Used in tonic water, to treat restless legs, or as a remedy for certain viruses.
Prescription quinoline derivatives:
Quinine
Quinidine
Hydroxychloroquine
Chloroquine

Supportive Care:

Manage airway, breathing, and circulation (ABCs).
Early use of epinephrine as a preferred pressor based on animal and chloroquine data.

Correct Endocrine/Metabolic Abnormalities:

Hypertonic Sodium: For wide QRS (use cautiously to avoid worsening hypokalemia).

Decontamination:

Key Findings:
Ocular toxicity is often delayed but can become permanent.
Quinine levels >15 are associated with increased ocular toxicity.
Quinine-induced blindness: https://pubmed.ncbi.nlm.nih.gov/3983356/
Hall AP, et al. Quinine-induced blindness. Br J Ophthalmol. 1997. doi:10.1136/bjo.81.12.1029
Recovery:
Vision may recover centrally first, then peripherally.
Hyperbaric oxygen therapy (HBO) is often used but remains debated.

Mechanism:
Tinnitus caused by microstructural changes in the outer hair cells of the cochlea and organ of Corti.
Vasoconstriction and prostaglandin inhibition contribute to decreased hearing.
Studies:
Jastreboff PJ, et al. Quinine-induced tinnitus in rats. Arch Otolaryngol Head Neck Surg. 1991. doi:10.1001/archotol.1991.01870220110020
Roche RJ, et al. Quinine induces reversible high-tone hearing loss. Br J Clin Pharmacol. 1990. doi:10.1111/j.1365-2125.1990.tb03704.x