Hydroxychloroquine and Chloroquine PhosphateRx

Trade Names: Plaquenil – hydroxychloroquine; Aralen – chloroquine

Drug Class: Antimalarial, DMARD

Preparations
Hydroxychloroquine: 200 mg tablet (155 mg base)
Chloroquine: 250 mg tablet (150 mg base)

Dose
Hydroxychloroquine: 5 mg/kg lean body weight. The usual initial dose is 400 mg/day (once daily or in divided doses). Dose may be reduced once a clinical response is achieved.
Chloroquine:  2-3 mg/kg lean body weight; usually not more than 250 mg daily

Indications: RA, SLE, discoid lupus erythematosus, palindromic rheumatism

Mechanism of Action: Unknown; may interfere with with macrophage presentation of antigen to T cells

Contraindications: Hypersensitivity to hydroxychloroquine, chloroquine, or 4-aminoquinolines

Precautions: Use caution in hepatic disease, psoriasis, and porphyria. Reports suggest that antimalarials may exacerbate psoriasis, but they were often safely used to treat psoriatic arthritis. G-6PD deficiency.

Monitoring: Hydroxychloroquine is the preferred antimalarial because it is less toxic to the eye. Chloroquine is sometimes tolerated by patients who do not tolerate hydroxychloroquine. Ophthalmologic (retinal and visual field) testing should be performed at baseline or soon after drug initiation and then at 6 -12  month intervals. Risks of retinal toxicity with hydroxychloroquine increase with a cumulative dose >800 g, age >70 years, daily dose >6.0 mg/kg, and impaired hepatic or renal function.

Pregnancy Risk: C

Adverse Effects
Common: GI irritation, headache, rash, itch, blurred vision owing to ciliary muscle dysfunction
Less common: Blue or black discoloration of skin or mucosa, reversible corneal opacities, irreversible retinal toxicity, neuromyopathy, cardiomyopathy, blood dyscrasias, ototoxicity, emotional changes, hemolysis with G6PD deficiency

Drug Interactions: Penicillamine: increased toxicity

Comments: In RA, most often used in combination with other DMARDs. Retinal toxicity is  rare with a dose of <5 mg/kg lean body weight/day and normal liver and renal function. When it does occur, retinal toxicity usually occurs after years of use and is slow in onset and irreversible.

Clinical Pharmacology: Good oral absorption, may be taken with food, partial hepatic metabolism and renal elimination, extensive tissue deposition with tissue concentrations 300 times that of plasma. Only 10% of a dose is excreted in 24 hours, and hydroxychloroquine remains in tissues for months.

Cost: $$$

BIBLIOGRAPHY
Marmor MF, Kellner U, Lai TY, et al. American Academy of Ophthalmology. Revised recommendations on screeningfor chloroquine and hydroxychloroquine retinopathy. Ophthalmology 2011;118:415-22. PMID: 21292109.