CHLOROQUINE &
HYDROXYCHLOROQUINE
Chloroquine
and hydroxychloroquine are nonbiologic drugs mainly used for malaria and in the rheumatic diseases. The mechanism
of the anti-inflammatory action of these drugs in rheumatic diseases is
unclear. The following mechanisms have been proposed: suppression of
T-lymphocyte responses to mitogens, decreased leukocyte chemotaxis,
stabilization of lyso-somal enzymes, inhibition of DNA and RNA synthesis, and
the trapping of free radicals.
Antimalarials
are rapidly absorbed and 50% protein-bound in the plasma. They are very
extensively tissue-bound, particularly in mela-nin-containing tissues such as
the eyes. The drugs are deaminated in the liver and have blood elimination
half-lives of up to 45 days.
Antimalarials
are approved for rheumatoid arthritis, but they are not considered very
effective DMARDs. Dose-response and serum concentration-response relationships
have been documented for hydroxychloroquine and dose-loading may increase rate
of response. Although antimalarials improve symptoms, there is no evidence that
these compounds alter bony damage in rheumatoid arthritis at their usual
dosages (up to 6.4 mg/kg/d for hydroxychloroquine or 200 mg/d for chloroquine).
It usually takes 3–6 months to obtain a response. Antimalarials are often used
in the treatment of the skin manifestations, serositis, and joint pains of
systemic lupus erythe-matosus, and they have been used in Sjögren’s syndrome.
Although
ocular toxicity may occur at dosages
greater than 250 mg/d for chloroquine and greater than 6.4 mg/kg/d for
hydroxychloroquine, it rarely occurs at lower doses. Nevertheless,
ophthalmologic monitoring every 12 months is advised. Other toxicities include
dyspepsia, nausea, vomiting, abdominal pain,rashes, and nightmares. These drugs
appear to be relatively safe in pregnancy.
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