Ridaura (Auranofin) - Description and Clinical Pharmacology

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DESCRIPTION

Ridaura (auranofin) is available in oral form as capsules containing 3 mg auranofin.

Auranofin is (2,3,4,6-tetra-O-acetyl-1-thio-ß-D-glucopyranosato-S-) (triethyl–phosphine) gold.

Auranofin contains 29% gold and has the following chemical structure:

Each Ridaura capsule, with opaque brown cap and opaque tan body, contains auranofin, 3 mg, and is imprinted with the product name RIDAURA. Inactive ingredients consist of benzyl alcohol, cellulose, cetylpyridinium chloride, D&C Red No. 33, FD&C Blue No. 1, FD&C Red No. 40, FD&C Yellow No. 6, gelatin, lactose, magnesium stearate, povidone, sodium lauryl sulfate, sodium starch glycolate, starch, titanium dioxide and trace amounts of other inactive ingredients.

CLINICAL PHARMACOLOGY

The mechanism of action of Ridaura (auranofin) is not understood. In patients with adult rheumatoid arthritis, Ridaura may modify disease activity as manifested by synovitis and associated symptoms, and reflected by laboratory parameters such as ESR. There is no substantial evidence, however, that gold-containing compounds induce remission of rheumatoid arthritis.

Pharmacokinetics: Pharmacokinetic studies were performed in rheumatoid arthritis patients, not in normal volunteers. Auranofin is rapidly metabolized and intact auranofin has never been detected in the blood. Thus, studies of the pharmacokinetics of auranofin have involved measurement of gold concentrations. Approximately 25% of the gold in auranofin is absorbed.

The mean terminal plasma half-life of auranofin gold at steady state was 26 days (range 21 to 31 days; n=5). The mean terminal body half-life was 80 days (range 42 to 128; n=5). Approximately 60% of the absorbed gold (15% of the administered dose) from a single dose of auranofin is excreted in urine; the remainder is excreted in the feces.

In clinical studies, steady state blood-gold concentrations are achieved in about three months. In patients on 6 mg auranofin/day, mean steady state blood-gold concentrations were 0.68 ±0.45 mcg/mL (n=63 patients). In blood, approximately 40% of auranofin gold is associated with red cells, and 60% associated with serum proteins. In contrast, 99% of injectable gold is associated with serum proteins.

Mean blood-gold concentrations are proportional to dose; however, no correlation between blood-gold concentrations and safety or efficacy has been established.