Chemistry - A water soluble gold salt, aurothioglucose contains approximately 50% gold. It is practically insoluble in alcohol and insoluble in vegetable oils. The commercial product is a 5% (50 mg/ml) suspension in sesame oil, 2% aluminum monostearate, and propylparaben is added as a preservative.
Storage/Stability/Compatibility - Protect from light and store between 15-30° C; avoid freezing. A five year expiration date is assigned after manufacture. Do not mix with any other compound when injecting.
Pharmacology - Aurothioglucose has anti-inflammatory, antirheumatic, immunomodulating, and antimicrobial (in vitro) effects. The exact mechanisms for these actions are not well understood. Gold is taken up by macrophages where it inhibits phagocytosis and may inhibit lysosomal enzyme activity. Gold also inhibits the release of histamine, and the production of prostaglandins. While gold does have antimicrobial effects in vitro, it is not clinically useful for this purpose.
Uses/Indications - In human medicine, gold compounds are used primarily as a treatment for rheumatoid arthritis that has not adequately responded to less toxic treatment modalities. In veterinary medicine (primarily small animal medicine), it use has been generally used for treating immune-mediated serious skin disorders such as pemphigus complex.
Pharmacokinetics - After IM injection, aurothioglucose is quite rapidly absorbed and peak serum concentrations are reached in 4-6 hours. It is distributed to several tissues (liver, kidney, spleen, bone marrow, adrenals, and lymph nodes), but highest levels are found in the synovium. In the plasma, 95% is bound to plasma proteins. Gold salts may be found in the epithelial cells in the renal tubules years after dosing has ended. Plasma half-lives increase in length after multiple doses have been given. These values have ranged from 21 - 168 hours in humans. Approximately 70% of a dose is excreted by the kidneys, while the remaining 30% is excreted in the feces.
There appears to be no correlation with serum levels and efficacy. It usually takes from 6-12 weeks for a beneficial effect to be noted after beginning therapy.
Contraindications/Precautions - Contraindications for chrysotherapy (gold therapy) include patients with renal or hepatic disease, SLE (lupus erythematosus, diabetes mellitus (uncontrolled), severe debilitation, and preexisting hematologic disorders.
The safety of aurothioglucose has not been established during pregnancy, it should only be used when the potential benefits outweigh the risks involved. Gold salts are distributed into milk and there have been reports of human infants developing rashes after nursing from mothers taking gold.
Adverse Effects/Warnings - Veterinary experience with aurothioglucose is limited. Pain at the injection site is common and some animals may develop thrombocytopenia with petechia and echymoses. One author (Kummel 1995) reports that four pemphigus canine cases treated with aurothioglucose that was given immediately after cessation of azathioprine, developed a fatal toxic epidermal necrolysis.
Adverse reactions seen in people include, mucocutaneous reactions which are fairly common (15-20%) and are characterized by rashes, (with or preceded by pruritis), and mucosal lesions (usually seen as a stomatitis). Hematologic reactions (thrombocytopenia, leukopenia, aplastic anemias), although rare in humans, can be life-threatening. Renal effects are generally mild and reversible with cessation of therapy if noted early. Proteinuria is an early sign associated with the proximal tubule damage that gold can cause. Reversible pulmonary infiltrates have been noted, but are reversible when therapy is discontinued. Enterocolitis, which may be fatal, has been reported in rare instances. Because of the serious nature of these adverse reactions, adequate patient monitoring is essential.
Overdosage - Overdosages resulting from a too rapid increase in dosages are exhibited by rapid development of toxic signs, primarily renal (hematuria, proteinuria) and hematologic (thrombocytopenia, granulocytopenia) effects. Other symptoms include: nausea, vomiting, diarrhea, skin lesions, and fever. Treat with dimercaprol (BAL) to chelate the gold and treat the hematologic and renal effects supportively.
Drug Interactions - Patients receiving aurothioglucose should generally not receive penicillamine, antimalarials, hydroxychloroquin, immunosuppresive or cytotoxic drugs (e.g., cyclophosphamide, methotrexate, azathioprine) other than corticosteroids, because of similar toxicity profiles.
a) 1 mg/kg IM once a week decreasing to once a month (Schultz 1986)
Monitoring Parameters -
1) Urinalysis—baseline, then weekly
2) CBC - baseline, then every 2 weeks
After the patient is on maintenance therapy, hemograms and urinalyses may be done every month or two.
Client Information - Clients should be instructed to notify the veterinarian if pruritis, rash, or diarrhea develops, or if the animal becomes ill or depressed.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Veterinary-Approved Products: None
Aurothioglucose Injection 50 mg/ml suspension (contains approximately 50% gold); in 10 ml vials; Solganal® (Schering); (Rx)
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