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Severe thrombocytopenia developed in a patient with rheumatoid arthritis during gold therapy. Increased numbers of marrow megakaryocytes, shortened 51Cr-labeled platelet survival and platelet phagocytosis by splenic macrophages indicated that thrombocytopenia was due to excessive platelet destruction. Aurothiomalate disodium antigenicity was demonstrated by increased lymphocyte blastogenesis, and accentuation of blood and splenic leukocyte migration in the presence of the gold salt. In vitro splenic immunoglobulin G (IgG) production was markedly increased, and a significant portion of the culture-produced IgG attached specifically to homologous platelets and platelet membranes. Serum antiplatelet antibodies could not be demonstrated, nor could it be shown that gold enhanced the binding of splenic-synthesized IgG to platelets. The data indicate an immunologic mechanism for gold-associated thrombocytopenia and permit speculation as to possible ways in which unidentified antigens may be involved in the pathogenesis in idiopathic thrombocytopenic purpura.

1. Male Wistar rats were given a single subcutaneous injection of gold sodium thiomalate and killed 7 days later. The binding of Au, Zn and Cu to the kidney and liver cytosolic proteins of control and gold-treated rats and determined. 2. In the renal cytosol of Au(I)- exposed rats, the binding of Cu to the low-molecular-weight (LMW) proteins increased by 62%, and to the high-molecular-weight (HMW) proteins the binding decreased by 54%. The incorporation of Cu into the liver cytosolic proteins increased, in both, the HMW and the LMW proteins. The binding of Zn into the renal cytosolic proteins was increased by 39% (HMW proteins) and 100% (LMW proteins). Au(I) had little effect on the binding of Zn to the cytosolic proteins in the liver. 3. It is suggested that the therapeutic action of gold complexes may be mediated, to some extent, by its effects on the metabolism of Cu and/or Zn.

The pharmacokinetics of oral gold (auranofin) in some respects resemble, and in other respects differ from, those of existing parenteral gold compounds such as gold sodium thiomalate (GST). This may in part relate to physicochemical differences as GST is a water-soluble polymeric compound in vitro whereas auranofin is lipid-soluble and characteristically monomeric. Furthermore, intramuscularly administered gold is greater than 95% bioavailable, whereas only 20 to 30% of an orally administered dose of auranofin is absorbed. Following a standard 50mg intramuscular injection of GST, serum gold concentrations rise sharply, peaking between 4 and 8 mg/L in approximately 2 hours and declining to an average of 3 mg/L by 7 days. With repeated injections of GST stable serum concentrations of gold (3 to 5 mg/L) are eventually achieved (usually within 5 to 8 weeks) although absolute concentrations may vary widely between patients. On the other hand, long term treatment with auranofin is associated with lower and more stable serum concentrations of gold (0.5 to 0.7 mg/L), on the standard dosing regimen of 6 mg daily. Both compounds are retained within the body for prolonged periods. However, the amount of gold retained with auranofin is significantly less compared with GST (less than 5% of a tracer dose of auranofin--about 20% of the absorbed dose--is retained by 100 days whereas the retention for a single labelled dose of GST over a similar interval is greater than 50%). Excretory patterns of GST and auranofin also differ. Most of an absorbed dose of GST (greater than 70%) is excreted by the kidneys whereas only 50% of an absorbed (15% of an administered) dose of auranofin is excreted in the urine. Both compounds are avidly bound by plasma proteins and auranofin shows a particularly strong association with circulating cellular elements. In human subjects, parenterally administered gold is widely distributed among bodily tissues, showing a predilection for tissues of the reticuloendothelial system as well as the kidney and adrenal cortex. Comparable studies in humans are not available for auranofin but animal studies have shown comparatively less affinity for the liver, kidney and spleen. Valuable insight has been gained in analysing the comparative pharmacokinetics of oral and injectable gold compounds. Unfortunately, attempts to correlate pharmacokinetic findings with clinical response or pharmacodynamic changes, as a whole, remain largely unsuccessful with these agents.

There have been three important double-blind studies evaluating the use of gold therapy in rheumatoid arthritis. Patients treated with gold have decreased number of joints with synovitis, decreased ring size, increased grip strength, and roentgenographic evidence of arrest or decrease in the progression of skeletal lesions. If a patient with active synovitis does not respond to nonsteroidal anti-inflammatory drugs after four months of treatment, he is a candidate for gold therapy. Maintenance gold therapy has been shown to sustain clinical improvement. Patients must be monitored with appropiate laboratory tests.

During studies of the metabolism of disodium aurothiomalate in patients with rheumatoid arthritis we have found that its pharmaceutical preparation. Myocrisin, contains 4 to 8% of free thiomalate. To establish whether the free thiomalate previously reported in plasma and urine of patients receiving Myocrisin is a true metabolite or results from this impurity, we prepared aurothiomalate containing 0.1% thiomalate. Intramuscular injection of the purified drug to 2 healthy subjects produced easily detectable levels of thiomalate in both plasma and urine; 7.7 and 9.8% respectively of the doses given were recovered in urine as free thomalate within 4 h. Thus, dissociation of disodium aurothiomalate does occur in vivo, releasing both gold and free thiomalate as potentially active forms.

After the administration of 70 mg and 50 mg aurothiomalate, respectively, to 2 patients with rheumatoid arthritis, significant amounts of gold appeared in breast milk.

The concentrations of gold in whole blood, serum, urine and blood cells of patients with rheumatoid arthritis were measured during 6 months of oral treatment either with Auranofin or placebo. Any adverse effects attributable to the treatments were also recorded. Although the time course of gold during Auranofin therapy was similar to that of injected gold, the blood and serum gold concentrations were significantly lower than those measured in patients receiving injected gold. Between 45 and 58% of Auranofin gold in the blood was associated with blood cells. In comparison, following injections of gold thiomalate, only about 4% of the gold was present in the blood cells. During the 6-month period, 2 patients receiving Auranofin withdrew because of diarrhoea and another because of rash. 1 placebo patient withdrew because of headaches. No laboratory evidence of haematological, renal or hepatic abnormality was encountered. It is suggested that the markedly lower concentrations of gold in the body sustained during treatment with Auranofin may be the critical factor towards a greater tolerance of the drug in the treatment of rheumatoid arthritis.

The purpose of this study is to demonstrate renal injuries by gold sodium thiomalate (G) with ultrastructual changes and gold deposition in kidney tissue using X-ray energy dispersive analysis (XEDA). Twenty-five mg of G containing 12.1 mg of Au was injected into rats intraperitoneally. The rats were divided into 5 groups. Group 1 was sacrificed 6 hours after the injection of G, and group 2 after 24 hours, group 3 after 72 hours and group 4 after 144 hours. Group 5 consisted of the control-rats which were provided with injections of saline. Gold contents in kidneys, liver, lungs and spleen were measured using the flameless atomic absorption method. XEDA was also performed in order to confirm the gold deposition in tissue. Among the organs, only the kidney showed remarkable changes with increased weight. Group 1 already showed marked azotemia which reached to the maximum level in group 3. The amount of gold content in the organs did not change significantly in spite of a marked reduction of serum gold concentration among the 4 groups. Histological examinations revealed marked degeneration and necrosis of pars recta in proximal tubules, although no prominent abnormalities of glomeruli could be observed. Using an electron microscope, many electron dense particles in lysosome were noticed, mainly in proximal tubules. We also found these particles in lysosome of glomerular epithelial cells. Using XEDA, these electron dense particles were demonstrated to be gold, since characteristic energy of gold was found. In conclusion, the kidney was shown to be the most accumulative organ of gold. G caused acute extensive necrosis of proximal tubules. Gold was demonstrated as electron dense particles in lysosomes mainly in proximal tubules, but also partly in glomeruli. Therefore, it was confirmed that a large amount of G had a strong nephrotoxic effect in rats.

The distribution of gold, copper and zinc in the livers and kidneys of female rats and hamsters was determined after intraperitoneal injection of sodium [195Au]-aurothiomalate. After five doses of sodium [195Au]-aurothiomalate (1 mg Au(I) per kg body weight), the hepatic and renal concentrations of Au were greater in rats than in hamsters. In the former species, treatment with the Au(I)-compound led to an increase in the Cu-concentration of the kidney and to the synthesis of a (Cu, Au)-metallothionein. In either species binding of Au to the hepatic metallothionein was insignificant. The renal (Cu, Au)-metallothionein from the sodium [195Au]-aurothiomalate-treated rat appeared to be extremely heterogeneous and was resolved into at least four components on ion exchange chromatography.

The binding of sodium [195Au]aurothiomalate (ATM) to whole cells of Mycoplasma arthritidis has been measured within the temperature range of 4 to 53 degrees C. The time course (kinetics) and the effect of varying the total concentration of free ATM in the suspension at 37 degrees C were also measured. The extent of binding at 37 degrees C leveled off after 30 min at approximately 65 nCi of [195Au]ATM per mg of membrane protein. The amount of ATM bound per cell appeared to be directly proportional to the concentration of free ATM in the range of 0.25 to 0.60 muCi of [195Au]ATM per ml. An Arrhenius plot showed two distinct regions with slopes of -0.56 degrees K/mg of protein (5 to 22 degrees C) and -2.78 degrees K/mg of protein (22 to 53 degrees C). The break in the Arrhenius plot corresponds to a temperature known to be related to a sudden change in mycoplasma membrane fluidity. Estimations of Scatchard binding constants and number of binding sites per membrane protein molecule resulted in 0.8 to 1.4 sites per molecule in the intact organisms compared to 1.4 to 1.8 sites in membrane fragments. The latter were purified by repeated washings in phosphate-buffered saline after alkaline lysis of the cells. It is suggested that ATM reacts with available protein sulfhydryl groups in the mycoplasmal membrane.

A method is described for determining the organic acid profile of synovial fluid. The method requires 50--100 microgram of sample and involves ion exchange for isolation of the acids followed by combined capillary column gas chromatography--mass spectrometry. Normal synovial fluid and synovial fluid from patients with rheumatoid arthritis show a similar qualitative pattern of acids (mainly fatty acids) resembling the pattern found in serum. The concentrations of the organic acids in the abnormal synovial fluids are 5--10 times higher than those in the fluid from the normal joints. In patients receiving treatment with gold thiomalate, free thiomalate was excreted in the urine. The release of this thiol upon gold therapy is of consequence for the further understanding of the mechanism of action of certain drugs against rheumatoid arthritis.

Our observations, as well as similarities between penicillamine and Myocrisin in clinical action and side effects in RA make it not unreasonable to think that thiomalate may have a penicillamine-like effect. Only a controlled clinical trial with thiomalate in RA can provide an answer to this question.

The preclinical profiles of auranofin (Ridaura), an oral chrysotherapeutic agent, parenteral gold sodium thiomalate, gold thioglucose, and their respective ligands were compared. Auranofin was more effective than gold sodium thiomalate in suppressing inflammation and stimulating cell-mediated immunity. In contrast to gold sodium thiomalate and gold thioglucose, auranofin inhibited cellular release of lysosomal enzymes, antibody-dependent cellular cytotoxicity, production of antibodies in adjuvant arthritic rats, and antibodies involved in cytotoxicity reactions. The respective ligands were without significant biologic activity. In rats, a higher fraction of gold was associated with blood cells after auranofin administration than after gold sodium thiomalate. The absorption, distribution, metabolism, and excretion of auranofin are uniquely different from other gold compounds.

Two normal males participated in a study designed to examine the disposition of gold given intravenously and intramuscularly as gold sodium thiomalate. Blood samples were collected for 30 days, urine and feces for ten. A triphasic decay pattern in plasma gold concentrations was observed. Terminal log-linear phases corresponded to a mean disposition half-life of 12.5 days. Absolute bioavailability of IM gold sodium thiomalate appears to be variable with one subject having complete absorption and the other absorbing 64% of the administered IM dose. The major route of elimination of an IV dose of gold sodium thiomalate is urinary excretion, with a mean of 35% of the dose found in the urine in ten days. Fecal elimination accounts for an additional 9.4% of the IV dose excreted in ten days, probably as a result of biliary secretion.

Suramin (250 mg/kg) and sodium aurothiomalate (100 mg/kg) both induced congenital malformations in the offspring following treatment of pregnant rats at either 8.5 or 9.5 days of gestation. Conceptuses from 9.5-day pregnant rats were cultured for 48 h in homologous serum to which either suramin or sodium aurothiomalate was added for the final 6 h. The presence of suramin up to 5 mg/ml had no effect on the protein content of yolk sacs at harvesting, but at 10 mg/ml caused a significant decrease. In contrast sodium aurothiomalate increased the protein content of yolk sacs at harvesting, in a concentration-dependent manner up to 100 micrograms/ml. Neither suramin nor sodium aurothiomalate significantly affected embryo protein content. When 125I-labelled polyvinylpyrrolidone was added to the culture serum for the final 6 h of culture, radioactivity was found in the yolk sac at harvesting, but not in the embryo. When suramin (2-10 mg/ml) was present for the final 6 h of culture, the quantity of radioactivity measured in the yolk sac at harvesting was significantly decreased in a concentration-dependent manner. No radioactivity was detected in the embryos. Sodium aurothiomalate had no effect on the uptake of 125I-labelled polyvinylpyrrolidone. When rat serum whose proteins were labelled with [3H]leucine was used as culture medium, radioactivity was found in the conceptus (both yolk sac and embryo) at harvesting. Suramin (5 mg/ml), present for the final or penultimate 6 h, significantly decreased the uptake of radioactivity into conceptuses and caused a significant increase in the proportion of the captured radiolabel that was associated with the yolk sac. Sodium aurothiomalate (25 or 500 micrograms/ml) had no effect on the total uptake of radio-label but caused a significant increase in the proportion of total radioactivity captured that was associated with the yolk sac. These data indicate that suramin, by interfering with both the uptake and intralysosomal digestion of protein, and sodium aurothiomalate, by inhibiting digestion of captured protein, disturb the normal pathway of yolk sac-mediated protein utilization with a consequent diminution of the supply of amino acids to the conceptus. The effects of suramin are seen only at high concentration, those of sodium aurothiomalate at much lower concentrations. It is likely that the two drugs exert their teratogenic action by their effects on the yolk sac nutritional pathway with resultant amino acid deprivation of the conceptus at a critical stage of development.

Double isotope-labelled auro thiomalate (Au195-C14-thiomalate) has been administered to mice and rats, and the excretory fate and tissue distribution have been studied. The results show that the gold and the thiomalate separate in vivo resulting in protein-bound gold and release of free thiomalate. About half of this thiol is excreted in the urine during the first day and the remaining half is taken up by the tissues. Thiomalate penetrates cellular membranes poorly, but is able to interact slowly with proteins (mixed disulphide formation). Part of the thiomalate which remains in the body is membrane bound. In contrast to penicillamine little thiomalate remains in circulation a few hours after administration. Gas chromatography--mass spectrometry has been used to search for the presence of free thiomalate in rheumatoid arthritis patients on Myocrisin (auro thiomalate) therapy. Thiomalate was found in their urine, but not in serum and synovial fluid 20 hours after administration. As thiomalate is released in the body after administration of Myocrisin. the question arises whether this thiol, like penicillamine, may have a beneficial effect in the treatment of rheumatoid arthritis.

The intramuscular (gold sodium thiomalate and aurothioglucose) and the orally (auranofin) administered gold compounds exhibit contrasting patterns of absorption, excretion and body tissue and fluid levels. The parenteral compounds are fully absorbed after injection but negligibly absorbed orally. Approximately 25% of the gold in auranofin is orally absorbed. Serum gold levels peak several hours after injection during conventional weekly treatment, attaining concentrations of 600-800 micrograms/dl, and then decline gradually, reaching 300-350 micrograms/dl before the next injection. Whole blood gold levels with auranofin vary from 10 to 90 micrograms/dl with doses of 1-9 mg/day. Blood gold levels plateau after 6-8 weeks with the injectable compounds and after 12 weeks with oral gold, reflecting the shorter blood half-life of gold sodium thiomalate (5.5 days) than of auranofin (17-26 days). A larger fraction of gold is within or attached to circulating blood cells, especially erythrocytes, with auranofin than with injectable gold. Fourty percent of the administered dose is excreted during injectable chrysotherapy, and 75-100% is recovered in excreta with auranofin. Parenteral gold is excreted primarily in urine (70%) while auranofin gold is recovered primarily in faeces (95%). Approximately 43% of intravenous radiolabelled gold sodium thiomalate is retained in the body at 60 days and 30% at 180 days; only 15% of radiolabelled auranofin remains at 10 days and less than 1% at 180 days. During injectable therapy, the total body burden of gold rises steadily; preliminary studies suggest minimal tissue accumulation with auranofin.

The excretory fate and plasma level of thiomalate were studied after intramuscular administration of auro-14C-thiomalate to 3 patients with rheumatoid arthritis. The gold and the thiomalate parts separated in vivo, and the free thiomalate was excreted in the urine, rapidly at first and then slowly. After one day about 60% of the 14C-label had been recovered in the urine. The plasma level also declined rapidly. The results are in complete agreement with those previously described in animal experiments.

The pharmacokinetics of intramuscular and oral gold compounds differ widely. Aurothioglucose and gold sodium thiomalate absorption is complete; 25% of auranofin (AF) is absorbed. Blood gold concentrations with conventional parenteral treatment generally peak between 600-800 microgram/dl the day of injection and decline gradually to about 300 micrograms/dl 7 days later. Levels range between 30 and 100 micrograms/dl, using 2-9 mg/d AF, and show little variation. A smaller percentage of gold is found in the cellular fraction of blood with I.M. than with oral gold. The blood half-life is approximately 6 days with gold sodium thiomalate, and 21 days with AF. Forty percent of the administered dose of injectable gold is excreted; depending upon dosage, 75-100% of oral gold is recovered in excreta, which is a combination of unabsorbed and excreted gold. Nearly 70% of parenteral gold is excreted in the urine and 30% in feces, while only 5% of AF is in urine and 95% in feces. The amount of gold retained following intravenous 195Au-labelled gold sodium thiomalate is 43% at 60 days and 25% at 250 days, but only 15% with oral radiolabeled AF 10 days after ingestion. Synovial fluid gold levels are much higher with parenteral than with oral gold but the blood-to-synovial fluid ratio is similar. Skin gold concentrations rise steadily with injectable but not oral treatment, but hair and nail accumulation is insignificant. Corneal, lens, and skin chrysiasis may develop with parenteral therapy, but has not been recognized with AF.