Auranofin is a
organogold compound classified by the
World Health Organization as an
antirheumatic agent. Pharmacotheraputic class: Auranofin is a organogold compound classified by the World Health Organization as an antirheumatic agent Pharmacokinetics:Auranofin is administered orally 25% of the gold in an orally administered dose of auranofin is absorbed from the GI tract. The drug is metabolized rapidly; unchanged auranofin does not appear in the blood following oral administration. Auranofin may undergo rapid deacetylation within the GI mucosa before absorption.
Peak blood gold concentrations of 0.025 mcg/ml are usually obtained within 2 hours following oral administration. Following multiple dosing, steady state is achieved within 8—12 weeks, although 13—16 weeks of therapy may be required in some patients. The mean steady-state gold concentrations in the blood of patients taking auranofin 6 mg daily was 0.68 +/- 0.45 mcg/ml. The mean blood-gold concentrations are proportional to dose, but no correlation between concentrations and either safety or efficacy has been established. Blood gold concentrations are generally higher than serum or plasma gold concentrations because the gold is sequestered with circulating cells. Gold distributes widely throughout the body and is found in the lymph nodes, bone marrow, spleen, adrenals, liver, and kidneys. Auranofin is approximately 60% plasma protein-bound, and gold appears to cross the placenta and to be distributed in breast milk in animals. Approximately 60% of an auranofin dose is excreted in the urine, and the remainder is excreted in the feces. The elimination half-life of auranofin following cumulative dosing is 26 days (blood) and 80 days (tissues). Mechanism of Action: Auranofin contains 29% gold. Like other gold compounds, auranofin exhibits antiarthritic, anti-inflammatory, and immunomodulating properties. Gold compounds are known as disease-modifying drugs. Auranofin may modify disease activity; reduced synovitis and ESR may occur. No substantial evidence, however, exists to support induction of rheumatoid arthritis (RA) remission by gold-containing compounds. Gold cannot reverse existing structural damage; best efficacy may occur in patients with active synovitis. The mechanism of the antiarthritic effects of auranofin is unknown. Auranofin appears to induce heme oxygenase 1 (HO-1) mRNA. Heme oxygenase 1 is an inducible heme-degrading enzyme with anti-inflammatory properties. Induction of HO-1 appears to suppress inflammatory responses in patients with RA. Auranofin incubation of synovial cells from patients with RA led to HO-1 expression induction in a concentration-dependent manner. Further, cells incubated with auranofin had significantly suppressed TNFalpha mRNA expression and COX-2 expression in a dose-dependent manner. Expression levels of TNFalpha mRNA and COX-2 protein were negatively correlated with the level of HO-1 protein. The impact of HO-1 induction inhibition by use of a HO-1 small interfering RNA was examined. Incubation of the cell lines with auranofin and HO-1 small interfering RNA reduced the induction of HO-1 mRNA as compared with incubation of the cells with only auranofin. Further, the TNF alpha mRNA concentration in the presence of HO-1 small interfering RNA was similar to the control value. Thus, auranofin appears to induce HO-1 mRNA, which reduces TNF alpha mRNA expression. Clinical applications: Gold compounds, which accumulate slowly in the body and, over time, reduce inflammation, especially related to rheumatoid arthritis, inflammatory bowel disease, psoriatic arthritis, membranous nephritis, lupus erythematosus and, infrequently, juvenile rheumatoid arthritis (JRA). Dosage forms &administration: Auranofin is administered as 2 x 3mg tablets daily, initially in divided doses then as a single daily dose if tolerated. If response is inadequate after 4-6 months this may be increased to 3mg three times a day. If there is no response after a further 3 months the treatment should be discontinued. Auranofin tablets should be taken with or just after food. Contraindications: • Most Significant Chronic Heart Failure, Diabetes Mellitus, Disease of Liver, Exfoliative Dermatitis, Hepatitis, Hypertension, Necrotizing Enterocolitis, Pregnancy, Pulmonary Fibrosis, Renal Disease • Significant Blood Dyscrasias, Colitis, Eczema, Leukopenia, Neutropenic Disorder, Severe Debilitation, Sjogren's Syndrome, Systemic Lupus Erythematosus, Thrombocytopenic Disorder, Urticaria
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