Gold, Injectable PreparationsRx

Trade Names:  Gold sodium thiomalate (Myochrysine), availability varies

Drug Class: DMARD

Preparations
Gold sodium thiomalate: 50 mg/mL

Dose: 10 mg i.m. test dose first week, 25 mg i.m. the next week, and then 25-50 mg/wk i.m. thereafter until response or a cumulative dose of 1 g. Once response is obtained, decrease frequency of injections to every 2 weeks for 2 months, then decrease frequency and maintain on 50 mg i.m. every 3–4 weeks. Most patients receive a maintenance dose of 50 mg monthly (every 4 weeks).

Indications: RA (largely obsolete)

Mechanism of Action: Unknown; probably interferes with normal macrophage function

Contraindications: Hypersensitivity to gold, severe renal or hepatic disease, blood dyscrasias

Precautions: Regular monitoring is required. Administer under medical supervision with facilities to treat anaphylaxis.

Monitoring: Perform baseline CBC, creatinine, LFTs and urinalysis. Check CBC, platelets, and urinalysis before each injection and LFTs periodically. Discontinue gold if there is a rapid fall in any blood parameter or if WBC is <4,000, granulocytes <1,500, or platelets <100,000. If there is persistent proteinuria (>300 mg/24 h), discontinue.

Pregnancy Risk: C

Adverse Effects
Common: Rash, itching, painful mouth ulcers, altered taste, proteinuria
Less common: Anaphylaxis, exfoliative dermatitis, glomerulonephritis, nephrotic syndrome, blue/black skin discoloration. Blood dyscrasias (aplastic anemia, agranulocytosis, thrombocytopenia) should be looked for because they may be severe, precipitous, and fatal. Hepatotoxicity, pulmonary fibrosis, and peripheral neuropathy are uncommon. Gold sodium thiomalate preparations have uncommonly been associated with a nitritoid reaction (flushing, sweating, dizziness) after the injection.

Drug Interactions: Potentially increased toxicity with other DMARDs

Patient Instructions: Frequent monitoring is essential. Do not become pregnant. Notify physician of rash and mouth sores.

Comments: Toxicity is common and can be severe. Largely obsolete and replaced by newer DMARDs. Onset of response is slow (6–12 weeks). If no response by 24 weeks, consider stopping. If there is a poor response after 1 g total dose, discontinue. A small minority of patients with RA responded well to intramuscular gold and tolerated it long term.

Clinical Pharmacology: Injectable gold is only given intramuscularly. Absorption is slow and erratic. Most is renally excreted. Plasma half-life is ~30 days, but gold is present in tissues months to years later.

Cost: $$ (Medication is relatively inexpensive, but the cost of weekly administration and laboratory work increases the total cost.)

BIBLIOGRAPHY

American College of Rheumatology Committee on Rheumatoid Arthritis Clinical Guidelines.Guidelines for the management of rheumatoid arthritis:2002 update. Arthritis Rheum 2002;46:328–346. PMID:11840435