Chloroquine and hydroxychloroquine

Last updated: October 19, 2023

Summarytoggle arrow icon

Chloroquine and hydroxychloroquine are drugs derived from the quinoline molecule. Both are used as antimalarial blood schizonticides, and hydroxychloroquine is also frequently used as an antirheumatic. Their mechanism of action is not entirely understood. Despite their varying therapeutic dosage and toxicity, both drugs have similar clinical indications and side effects. One of their most serious side effects is retinal toxicity, referred to as 4AQ retinopathy or chloroquine retinopathy, which must be screened for in all cases of long-term use.

Pharmacodynamicstoggle arrow icon

The precise mechanisms of action are unknown, but the following are the most widely accepted hypotheses:

Adverse effectstoggle arrow icon

Patients using long-term chloroquine/hydroxyhloroquine should have regular ophthalmological examinations.

We list the most important adverse effects. The selection is not exhaustive.

Chloroquine maculopathytoggle arrow icon

Indicationstoggle arrow icon

Mechanism of resistancetoggle arrow icon

  • Attributed to the development of membrane efflux pumps, which decrease the intracellular concentration of the drug.
  • Occurs especially in P. falciparum

Referencestoggle arrow icon

  1. Chong CR, Sullivan DJ. Inhibition of heme crystal growth by antimalarials and other compounds: implications for drug discovery. Biochem Pharmacol. 2003; 66 (11): p.2201-2212.
  2. Fox RI. Mechanism of action of hydroxychloroquine as an antirheumatic drug. Semin Arthritis Rheum. 1993; 23 (2 Suppl 1): p.82-91.
  3. UpToDate. Chloroquine: Drug Information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 1, 2017. Accessed: April 9, 2017.
  4. UpToDate. Hydroxychloroquine: Drug Information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 1, 2017. Accessed: April 9, 2017.
  5. Aghahowa S, Obianwu H, Isah A, Arhewoh I. Chloroquine-induced Pruritus. Indian J Pharm Sci. 2010; 72 (3): p.283.doi: 10.4103/0250-474x.70471 . | Open in Read by QxMD
  6. Lior Jankelson, Giorgio Karam, Matthijs L. Becker, Larry A. Chinitz, and Meng-Chiao Tsai. QT prolongation, torsades de pointes, and sudden death with short courses of chloroquine or hydroxychloroquine as used in COVID-19: A systematic review. Heart Rhythm. 2020.

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