sodium thiosulfate
Meaning of sodium thiosulfate: One simple reaction, a sulfur atom loosely held and easily given away, explains a list of uses that otherwise looks unrelated.
Definition of sodium thiosulfate
Sodium thiosulfate is an inexpensive inorganic salt given by vein as an antidote to cyanide poisoning and to guard against certain drug toxicities. It supplies sulfur to an enzyme that converts cyanide into thiocyanate, a far less harmful compound the kidneys remove. It is also used to reduce the risk of hearing loss caused by cisplatin, and applied to the skin for a common fungal rash.
How does it work against cyanide?
Cyanide kills by locking onto an enzyme inside every cell that is needed for the final step of using oxygen. Cells are surrounded by oxygen they can no longer touch, and the organs that burn it fastest, the heart and the brain, fail first. The body already has an escape route. An enzyme called rhodanese moves a sulfur atom onto cyanide, producing thiocyanate, which the kidneys pass into the urine. What limits that reaction is the supply of spare sulfur, not the enzyme itself. This salt supplies sulfur in bulk and the reaction speeds up accordingly. The effect builds over minutes rather than instantly, which is why it was traditionally paired with a faster acting agent. The sodium half of the name contributes nothing to the action and only makes the compound dissolve.
What else is it used for?
| Use | What the compound is doing |
|---|---|
| Cyanide poisoning | Feeding sulfur to the enzyme that disarms cyanide |
| Hearing loss from cisplatin in children | Mopping up reactive platinum before it reaches the inner ear |
| Calciphylaxis in advanced kidney failure | Easing painful skin ulcers, by a mechanism still argued over |
| Tinea versicolor | Applied to the skin as an antifungal solution |
The list looks scattered because it is: the same simple chemistry, a sulfur atom loosely held and readily given away, happens to be useful in unrelated situations. Nothing here makes it an anticancer drug.
Why does timing matter alongside cisplatin?
Sodium thiosulfate reacts readily with platinum. That reactivity is exactly what protects the inner ear, and exactly what could blunt the cancer treatment if the two met inside a tumor. The compound is therefore given after a deliberate delay, once the platinum has had time to act where it is wanted. Its established use is in children treated for tumors outside the nervous system, and it is approached more cautiously when disease has already spread, for the same reason. The drug has no effect on a tumor of its own.
Also known as
Used in a sentence
Sodium thiosulfate was given intravenously as part of the treatment for suspected cyanide exposure.
Good to know
Sodium thiosulfate reacts with platinum, so the chemistry that protects hearing could also reduce the effect of cisplatin on a tumor, which is why the two are separated in time rather than given together.
Word origin
Where “sodium thiosulfate” comes from
The prefix thio- comes from the Greek theion, meaning sulfur, and marks a compound in which sulfur has taken the place of an oxygen atom. Thiosulfate is sulfate with that swap made.