Don’t be surprised that gold is used to treat diseases as it is medicine itself

Gold and various gold compounds have been used for medicinal purposes for centuries. Records show that China used gold in drug as early as 2500 BC, which might be the legendary "Golden Elixir". The bacteriologist Dr. Koch observed the antitubercular activity of in-vitro gold compound at the beginning of the 20^th century, therefore, he used it to treat human and bovine tuberculosis. The thiomalic acid gold compound has significant effects in curing the lesions caused by mycoplasma and Leishmaniasis within the therapeutic concentration range during normal treatment. Years after the gold compounds were used to treat tuberculosis, clinicians found that gold compounds did not completely kill bacterial diseases, or stop growth of bacteria or disease progression in tuberculosis patients, therefore, they stopped the use of gold compounds in antibacterial treatment. On the contrary, their studies found that various gold compounds could effectively slow down the progression of rheumatoid arthritis. Anti-inflammatory drugs represented by various oral gold thiosulfate compounds were developed in 1980s and rapidly spread.

Application of gold in ancient medicine could trace back to the remote ages when people always thought that gold could cure all diseases. The "gold beverage" taken by people in the 13^th century was called cure-all. There is the therapeutic method of allaying fear of children with gold foil among the Chinese people. Gold is also widely used as material for dentures. However, a large amount of gold has corrosion toxicity, for example, people committed suicide by swallowing gold in ancient times. Gold is important material for artificial organs and surgical implants owing to the good chemical stability, biological compatibility and mechanical properties compared to other noble metal elements. The exploration of mysteries of the nervous system with the microprobe made of gold and other noble metals has achieved remarkable results. Nerve repair and heart pacemaker, etc. all use gold and noble metals and the alloy materials thereof.

In modern medical chemistry, the radioisotopes of gold are widely applied in radiation therapy. Gold can exist in the radioactive irradiated volume in the form of granule or colloid, therefore, based on this feature, colloidal gold is used in radiotherapy of pleural or peritoneal exudate and bladder cancer. Gold vapor laser can be used to treat gastric cancer and lung cancer. On the other hand, colloidal gold is also used for various diagnostic purposes, such as bone marrow scan or organ radiography: colloidal gold is fully loaded in the human organ for study, and then the scintigraphy is used for observation. Also, gold foil can be used to treat burned skin.

Auranofin is the most famous modern preparation containing gold in the tablets, with main ingredient of univalent mercapto-compound preparation of gold, and it is mainly used for active rheumatoid arthritis, especially indicated for patients who do not have obvious effect in using or are intolerant to nonsteroidal anti-inflammatory drugs, with retail price of RMB 229/box. Regarding the pharmacological mechanism of action, it can delay progression of disease of rheumatoid arthritis and improve the symptoms. Auranofin cannot eliminate the osteoarticular damage that has occurred, but may stop or delay further joint damage. However, auranofin acts slowly, taking 3 months averagely or even 5-6 months, therefore, nonsteroidal anti-inflammatory drug shall also be taken while taking auranofin, so as to alleviate pains of patients caused by rheumatoid arthritis before auranofin acts.

Regarding the pharmacokinetics, 25% of the gold contained in auranofin will be absorbed after oral administration, wherein, about 40% will bind to red blood cells, and 60% will bind to serum proteins. Over 90% of auranofin will be excreted through feces after taking, and the other small part will be excreted through urine. In the case of taking a constant amount of auranofin for a long time, the gold concentration in blood will peak in 12 weeks, and keep stable, however, the correlation between drug concentration in blood and efficacy or adverse action incidence has not been proved. The concentration of auranofin in synovial fluid is half that in plasma, and the concentration is high in inflammatory synovial tissues, with a large amount existing in synovial cells. In addition, auranofin also has certain toxicity and danger. The relevant FDA package insert specially warns that auranofin can cause gold toxicity, with symptoms including fall in hemoglobin, leukopenia, granulocytes, decrease in platelets, proteinuria, hematuria, pruritus, rash, stomatitis or persistent diarrhea, etc.

To sum up, gold is not only a metallic equivalent, but also can be used as a drug. Auranofin is an oral drug for rheumatoid arthritis on the market; its clinical application is reduced with R&D of various modern novel drugs, however, studies on auranofin show that it may also be conductive to the treatment of many diseases, and researchers have found that it might be a novel drug candidate for cancer treatment and antimicrobial infection. Don’t be surprised that gold is used to treat diseases as it is medicine itself.

By Jin Senshui