For decades, specific gold compounds, often called "gold salts," were a prominent treatment for inflammatory diseases, particularly rheumatoid arthritis. While the use of these traditional drugs, like gold sodium thiomalate, has largely declined, the application of gold in medicine is evolving with the rise of gold nanoparticle technology.
The Era of Gold Salts in Medicine
Gold compounds like gold sodium thiomalate and auranofin were a type of disease-modifying anti-rheumatic drug (DMARD) used to treat rheumatoid arthritis (RA). These medications worked by suppressing the overactive immune response responsible for the joint inflammation seen in RA.
Notable gold-containing medicines
Historically, the most significant gold-containing medicines were:
- Gold sodium thiomalate (brand names: Myochrysine, Aurolate): This was an injectable form of gold salt, administered via intramuscular injection. The treatment regimen typically involved weekly injections for several months, with the interval lengthening as the patient responded. The manufacturer of Myochrysine, Sanofi, discontinued it worldwide in 2019.
- Aurothioglucose (brand name: Solganal): Another injectable gold compound, aurothioglucose was also used for rheumatoid arthritis. Like Myochrysine, it is now no longer generally available in the U.S..
- Auranofin (brand name: Ridaura): This is an oral form of gold that continues to be available in some regions. It is generally less effective than the injectable forms but also associated with fewer severe side effects.
The decline of traditional gold therapy
The use of these traditional gold salts significantly decreased starting in the 1980s. Several factors contributed to this shift:
- Significant side effects: Gold salts were associated with a high incidence of adverse effects, including severe skin rashes (dermatitis), mouth sores (stomatitis), and kidney damage (proteinuria). Long-term use could also cause a permanent bluish-gray skin discoloration known as chrysiasis.
- Slow onset of action: The therapeutic effects of gold salts were not immediate, often taking months to become noticeable, unlike newer, faster-acting therapies.
- Development of newer DMARDs: The introduction of newer, more effective, and better-tolerated DMARDs and biologic drugs, such as methotrexate, significantly reduced the need for gold salts.
Modern Applications: Gold Nanoparticles
In contemporary medicine, the focus on gold has shifted from traditional gold salts to sophisticated applications involving gold nanoparticles (GNPs). These are tiny, engineered gold particles used in diagnostics and therapies, not as an active drug compound in the traditional sense, but as a therapeutic platform or delivery vehicle.
Uses of gold nanoparticles in medicine
- Cancer therapy: GNPs can be used for photothermal therapy, where they are injected and then heated with a laser to destroy tumor cells. They also serve as radiosensitizers, amplifying the effects of radiation therapy to kill cancer cells while sparing normal tissue.
- Drug delivery: GNPs can be engineered as sophisticated delivery systems to carry drugs directly to a targeted area, such as a tumor. This minimizes systemic side effects and increases the therapeutic index of the loaded drug.
- Diagnostics: The vibrant color of gold nanoparticles is used in many rapid diagnostic tests, such as at-home pregnancy tests and COVID-19 tests, to indicate a positive result.
Comparison: Gold Salts vs. Gold Nanoparticles
This table highlights the key differences between the older, traditional gold salts and modern gold nanoparticle applications.
| Feature | Traditional Gold Salts (e.g., Myochrysine, Auranofin) | Modern Gold Nanoparticles (GNPs) |
|---|---|---|
| Application | Treatment of inflammatory conditions, primarily rheumatoid arthritis | Drug delivery, cancer therapy, diagnostics |
| Form | Gold compounds (ionic gold) that actively suppress the immune system | Engineered particles that act as therapeutic platforms or carriers |
| Mode of Action | Inhibits inflammatory processes by altering the immune system; mechanism not fully understood | Delivers therapeutic agents, amplifies radiation, generates heat, or serves as a diagnostic marker |
| Route of Administration | Injectable (intramuscular) or oral capsules | Injectable (intravascular), topical, or oral, depending on application |
| Safety Profile | High incidence of severe side effects, including renal and hematologic issues | Initial studies show good safety profiles, but further long-term research is ongoing |
| Current Status | Largely discontinued due to toxicity and newer options; some oral forms still exist | A burgeoning field of research with numerous clinical trials underway for novel applications |
Understanding the mechanism and risks
The pharmacological mechanism of traditional gold compounds is still not entirely understood, but research suggests it involves inhibiting phagocytic and chemotactic responses of immune cells and suppressing the production of inflammatory cytokines. In contrast, the mechanism of gold nanoparticles depends on their specific design and function, such as enhancing radiation effects or delivering payloads.
The risks associated with traditional gold salts were significant, leading to strict monitoring requirements, such as regular blood and urine tests. Severe toxicities affecting the bone marrow and kidneys were particular concerns. With nanoparticles, the focus shifts to ensuring biocompatibility and understanding their long-term fate and potential accumulation within the body, though initial safety data from clinical trials appears promising.
Conclusion
Gold's role in medicine has undergone a dramatic transformation, from a historical, and often toxic, treatment for rheumatoid arthritis to an innovative material at the forefront of nanomedicine research. While older gold salts have mostly been phased out in favor of more effective and safer therapies, the development of gold nanoparticles has opened up new frontiers for targeted drug delivery, advanced cancer treatments, and improved diagnostic tools. This evolution underscores the continuous effort to refine medical treatments and find new applications for elements with unique biological properties. For additional information on gold therapy, consider consulting a comprehensive medical resource like ScienceDirect's overview of Gold Therapy.
