GOLD SODIUM THIOMALATE

GOLD SODIUM THIOMALATE (thye-oh-mah'late) Myochrysine  Classifications: gold compound; antimuscarinic; immunomodulator; disease-modifying antirheumatic drug (dmard); Therapeutic:dmard; gold compound Prototype: Auranofin Pregnancy Category: C

Availability

50 mg/mL injection

Action

Water-soluble gold compound. Drug appears to act by suppression of phagocytosis, altered immune responses, and possibly by inhibition of prostaglandin synthesis.

Therapeutic Effect

Has immunomodulatory and antiinflammatory effects.

Uses

Selected patients (adults and juveniles) with acute rheumatoid arthritis.

Unlabeled Uses

Psoriatic arthritis, Felty's syndrome.

Contraindications

History of severe toxicity from previous exposure to gold or other heavy metals; severe debilitation; SLE, Sjögren's syndrome in rheumatoid arthritis; renal disease; hepatic dysfunction, history of infectious hepatitis or hematologic disorders; uncontrolled diabetes or CHF; pregnancy (category C).

Cautious Use

History of drug allergies or hypersensitivity, hypertension.

Route & Dosage

Rheumatoid Arthritis Adult: IM 10 mg wk 1, 25 mg wk 2, then 25–50 mg/wk to a cumulative dose of 1 g (if improvement occurs, continue at 25–50 mg q2wk for 2–20 wk, then q3–4wk indefinitely or until adverse effects occur) Child: IM 10 mg test dose, then 1 mg/kg/wk or 2.5–5 mg for wk 1 and 2, followed by 1 mg/kg q1–4wk (max: single dose 50 mg)

Administration

Intramuscular

• Agitate vial before withdrawing dose to ensure uniform suspension.
• Give deep into upper outer quadrant of gluteus maximus with patient lying down. Patient should remain recumbent for at least 30 min after injection because of the danger of "nitritoid reaction" (transient giddiness, vertigo, facial flushing, fainting).
• Observe for allergic reactions.
• Store in tight, light-resistant containers at 15°–30° C (59°–86° F). Do not use if any darker than pale yellow.

Adverse Effects (≥1%)

CNS: Dizziness, syncope, sweating, flushing. CV: Bradycardia. GI: Hepatitis, metallic taste, stomatitis, nausea, vomiting. Hematologic: Agranulocytosis, aplastic anemia, eosinophilia (all rare). Urogenital: Nephrotic syndrome, glomerulitis with hematuria, proteinuria. Skin: Transient pruritus, erythema, dermatitis, fixed drug eruption, alopecia, shedding of nails, gray to blue pigmentation of skin (chrysiasis). Special Senses: Gold deposits in ocular tissues, photosensitivity. Body as a Whole: Peripheral neuritis, angioneurotic edema, interstitial pneumonitis, anaphylaxis (rare). Respiratory: Pulmonary fibrosis.

Interactions

Drug: antimalarials, immunosuppressants, penicillamine, phenylbutazone increase risk of blood dyscrasias.

Pharmacokinetics

Absorption: Slowly and irregularly absorbed from IM site. Peak: 3–6 h. Distribution: Widely distributed, especially to synovial fluid, kidney, liver, and spleen; does not cross blood–brain barrier; crosses placenta. Metabolism: Not studied. Elimination: 60–90% of dose ultimately excreted in urine; also eliminated in feces; traces may be found in urine for 6 mo. Half-Life: 3–168 d.

Nursing Implications

Assessment & Drug Effects

• Lab tests: Prior to each injection, urinalysis for protein, blood, and sediment. Withhold drug and notify physician promptly if proteinuria or hematuria develops. Also do baseline Hgb and RBC, WBC count, differential count, platelet count before initiation of therapy and at regular intervals.
• Note: Rapid reduction in hemoglobin level, WBC count below 4000/mm³, eosinophil count above 5%, and platelet count below 100,000/mm³ signify possible toxicity.
• Interview and examine patient before each injection to detect occurrence of transient pruritus or dermatitis (both are common early indications of toxicity), stomatitis (sore tongue, palate, or throat), metallic taste, indigestion, or other signs and symptoms of possible toxicity. Interrupt treatment immediately and notify physician if any of these reactions occurs.
• Observe for allergic reaction, which may occur almost immediately after injection, 10 min after injection, or at any time during therapy. Withhold drug and notify physician if observed. Keep antidote dimercaprol (BAL) on hand during time of injection.

Patient & Family Education

• Therapeutic effects may not appear until after 2 mo of therapy.
• Notify physician of rapid improvement in joint swelling; this is indicative that you are closely approaching drug tolerance level.
• Use protective measures in sunlight. Exposure to sunlight may aggravate gold dermatitis.
• Notify physician at the appearance of purpura or ecchymoses; this is always an indication for doing a platelet count.
• Know possible adverse reactions and report any symptom suggestive of toxicity immediately to physician.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug