Antimalarials

Antimalarials

Hydroxychloroquine (Plaquenil) and chloroquine (Ara-len) are 4-aminoquinoline antimalarial drugs that pos-sess modest DMARD activity. They are indicated for the treatment of rheumatoid arthritis and systemic lu-pus erythematosus; The onset of action of these drugs is longer than that of other DMARDs, and their side ef-fects are relatively mild. Because of this, these agents show promise as ingredients of combination therapies for rheumatoid arthritis.

Basic Pharmacology

Hydroxychloroquine and chloroquine are similar in ac-tivity; however, hydroxychloroquine has a lower inci-dence of ocular side effects and is used more frequently. These drugs are weak bases that enter and interfere with the functioning of lysosomes and other subcellular compartments of T- and B-lymphocytes, monocytes, and macrophages. This in turn inhibits the ability of these cells to produce and release inflammatory cytokines and hydrolytic enzymes.

Adverse Effects

Skin rashes and pruritus are common adverse effects of the 4-aminoquinoline antimalarials, as are GI effects. The incidence of the most serious toxic reaction, irre-versible retinopathy with resultant blindness, is dose re-lated and can be minimized by maintaining a daily dose of hydroxychloroquine less than 6.5 mg/kg or chloro-quine less than 4 mg/kg. Eye examinations should be performed regularly during treatment with these drugs. Severe hematological toxicity (neutropenia, thrombo-cytopenia, aplastic anemia) is rare. Reversible side ef-fects observed during high-dose, long-term therapy with the aminoquinolines include lichenoid skin lesions, leukopenia, neuromyopathy, hair loss, sensitivity to sun-burn, and changes in the electrocardiogram.

Contraindications and Drug Interactions

The aminoquinolines accumulate in lung, kidney, and liver; thus, any preexisting pathology in these tissues contraindicates their use. Similarly, any ocular pathol- ogy precludes their use. Psoriasis and porphyria are fre-quently exacerbated by the administration of the aminoquinolines.

Aminoquinolines can increase plasma concentra-tions of penicillamine, hence the potential for serious hematological or renal toxicity. Similarly, aminoquino-lines can increase digoxin levels. Gold and an amino-quinoline probably should not be administered concur-rently because of the propensity of each to produce dermatitis.