United States of America. Administration of intravenous sodium thiosulfate has been shown to prevent hearing loss associated with carboplatin given to treat brain tumours.⁽²⁾

Researchers report on 29 patients with malignant brain tumours who were treated with carboplatin in conjunction with osmotic blood-brain barrier disruption to enhance delivery of carboplatin, followed two hours later by intravenous sodium thiosulfate (4 g to 20 g/m2). Animal studies have shown that sodium thiosulfate can cause seizures if given when the blood-brain barrier is open, hence the two-hour interval.

In a previous sample of 19 patients similarly treated who were not given sodium thiosulfate, 15 (79%) suffered profound high frequency hearing loss caused by carboplatin. In comparison, fewer patients in the sodium thiosulfate group suffered hearing loss, and those who did experience some loss were able to undergo more courses of carboplatin before any loss occurred.

Sodium thiosulfate appears to bind to the platinum in carboplatin before it has a chance to harm the inner ears. It is the first drug shown to prevent chemotherapy-induced hearing loss.

References:

1) The Pharmaceutical Journal Vol. 261, p.77, 18 July 1998.
2) Journal of Pharmacology and Experimental Therapeutics 286: 77 (1998).