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Systematic (IUPAC) name
CAS number 118-42-3
ATC code P01BA02
PubChem 3652
Chemical data
Formula C18H26ClN3O 
Mol. mass 335.872 g/mol
Pharmacokinetic data
Bioavailability  ?
Metabolism  ?
Half life 1-2 months
Excretion Renal
Therapeutic considerations
Pregnancy cat.

D (Au), C (U.S.)

Legal status

POM (UK), ℞-only (U.S.)

Routes Oral

Hydroxychloroquine is an antimalarial drug, sold under the trade name Plaquenil®, also used to reduce inflammation in the treatment of Rheumatoid arthritis (see Disease-modifying antirheumatic drugs) and lupus.


Classification and use

Hydroxychloroquine is classified as an anti-malarial medication, and is one of a number of drugs which have been used for many years in the treatment of malaria. It is useful in treating systemic lupus erythematosus as well as rheumatoid arthritis and Sjogren's Syndrome (all rheumatic disorders) though their action with these conditions is not understood, though they are believed to reduce T-lymphocyte transformation and chemotaxis. It is also speculated that this drug alters the lysosomal pH in antigen presenting cells, further helping curb inflammation. With arthritis, the benefits will take several weeks to occur.



For prevention of malaria, the usual adult dose is 400 milligrams per seven days, on the same day, begun two weeks prior to exposure, or two 400 milligrams doses taken six hours apart. Suppressive therapy continues for eight weeks after leaving the contaigious area. For acute malaria is either a single 800 milligram dose, or 800 milligrams followed by 400 milligrams six to eight hours later, and 400 milligrams once per day for two consecutive days. The children's dose will depend on the weight of the child, but should be supervised by a doctor.

Lupus Erythematosus

The adult starting dose is 400 milligrams one to two times daily, for several weeks or months, depending on the reaction. This may be reduced to 200 to 400 milligrams per day for maintenance. With systemic lupus, it is especially useful in relieving skin inflammation, hair loss, oral sores, fatigue and joint pain, as well as preventing relapse.

Rheumatoid Arthritis

The adult starting dose is 400 to 600 milligrams per day with food or milk; with improvement (between four to twelve weeks) the maintenance dose is 200 to 400 milligrams daily. Hydroxychloroquine is not safe for the treatment of juvenile arthritis.

Side Effects

Side effects are difficult to anticipate, and should be reported to a doctor immediately if new symptoms develop or old symptoms change in intensity. Generally side effects are not common, but can include (for short-term treatment of acute malaria) abdominal cramps, diarrhea, heart problems, reduced appetite, headache, nausea and vomiting. The symptoms for prolonged treatment of lupus or arthritis include the acute symptoms, plus altered eye pigmentation, acne, anemia, bleaching of hair, blisters in mouth and eyes, blood disorders, convulsions, significant vision difficulties, diminished reflexes, emotional changes, excessive coloring of the skin, hearing loss, hives, itching, liver problems or failure, loss of hair, muscle paralysis, weakness or atrophy, nightmares, psoriasis, reading difficulties, tinnitus, skin inflammation and scaling, skin rash, vertigo, and weight loss. Hydroxychloroquine can worsen existing cases of both psoriasis and porphyria.

The most common side effects are a mild nausea and occasional stomach cramps with mild diarrhea. The most serious side effect is a rare toxicity in the eye (generally with chronic use), and requires regular screening even when symptom-free. The daily safe maximum dose for eye toxicity can be computed from one's height and weight using this calculator.

Toxicity from hydroxychloroquine may be seen in two distinct areas of the eye, the cornea, and the macula. The cornea may become affected (relatively commonly) by an innocuous vortex keratopathy and is characterized by whorl-like corneal epithelial deposits. These changes bear no relationship to dosage and are usually reversible on cessation of hydroxychloroquine.

The macular changes are potentially serious and are related to dosage and length of time taking hydroxychloroquine. Established maculopathy is characterized by moderate reduction of visual acuity and an obvious "bulls eye" macular lesion. End stage maculopathy is characterized by severe reduction in visual acuity and severe atrophy of the retinal pigment epithelium.

A type of enzyme deficiency (enzyme G6PD) found most frequently in those of African descent can develop into severe anemia and should also be monitored. Children are more sensitive to hydroxychloroquine than adults are, and small doses can be potentially fatal.

Hydroxychloroquine generally does not have significant interactions with other medications but care should be taken if combined with medication altering liver function as well as Aurothioglucose (Solganal), Cimetidine (Tagamet) or Digoxin (Lanoxin). It will transfer into breastmilk and should be used with care by pregnant or nursing mothers.

Symptoms of overdose can occur within a half-hour of taking the medication. Overdose symptoms include convulsions, drowsiness, headache, heart problems or heart failure, difficulty breathing and vision problems.


    • Health Square article on Hydroxychloroquine
    • Medicinenet article on Hydroxychloroquine
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hydroxychloroquine". A list of authors is available in Wikipedia.
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