Sodium Thiosulfate (Pedmark): Cisplatin Ototoxicity Protection, Pediatric Dosing & Real-World Cost Guide.

Cisplatin kills cancer cells by damaging their DNA, but it also damages the hair cells in the cochlea (inner ear) through two pathways: direct DNA damage and reactive oxygen species (ROS), which are toxic molecules. A landmark 2017 trial showed that children who received sodium thiosulfate during cisplatin had a 71% rate of normal hearing one year later, compared to only 29% in the untreated group ^[4]. The federal receipt is clear: one IV infusion during chemotherapy can prevent permanent hearing loss ^[1].

Sodium thiosulfate works like a chemical bodyguard. It enters cells through a natural transporter (sodium sulfate cotransporter 2) and increases glutathione, the body's master antioxidant, by 340% ^[1]. This shields the delicate hair cells from oxidative stress while cisplatin still kills the cancer. Think of it as giving the inner ear a protective shield while the chemotherapy does its job elsewhere ^[1].

The timing matters. Sodium thiosulfate must be given during or within 6 hours of cisplatin to be effective ^[9]. It takes 15–30 minutes to infuse and has minimal side effects in children with normal kidney function. The trade-off is simple: one extra IV line and 30 minutes of infusion time to protect hearing for life ^[4].

The FDA-approved dosing is 12.5 g per 100 mL IV infusion ^[9]. There is no oral tablet or liquid form—it must be given intravenously. Each infusion takes 15–30 minutes and is given in the oncology clinic during the same visit as cisplatin or immediately afterward ^[9]. The protocol is straightforward: one infusion per chemotherapy cycle, repeated as long as cisplatin is being used ^[1].

Sodium thiosulfate works by binding to cisplatin molecules in the bloodstream and tissues. The window is tight: it must be given during or within 6 hours of cisplatin to be effective ^[9]. After 6 hours, most of the cisplatin has already entered cells, and sodium thiosulfate cannot protect the inner ear ^[1]. This is why timing coordination between the oncology and pharmacy teams is critical ^[4].

For a typical childhood cancer protocol (4–8 cycles of cisplatin over 3–6 months), your child will receive 4–8 infusions of sodium thiosulfate. Each infusion is a single dose; there is no daily pill or weekly injection ^[9]. The oncology team will schedule it automatically if it is part of the treatment plan ^[1].

In clinical trials, the most common side effects were nausea and vomiting, which occurred in fewer than 20% of children and were easily managed with anti-nausea medication ^[1][4]. Some children report a sulfur-like taste during or after the infusion, which fades within hours ^[9]. Serious side effects like electrolyte imbalances or allergic reactions are rare in children with normal kidney function ^[1].

Sodium thiosulfate works by increasing sulfate and sulfite levels in the blood. In children with normal kidneys (eGFR >60), these are filtered out naturally within 24 hours ^[9]. The body tolerates this well because sulfites are naturally present in foods like dried fruit and wine ^[1]. The mechanism is safe: the drug does not accumulate or cause organ damage in healthy kidneys ^[3].

The only real safety concern is severe kidney disease. If your child has an eGFR <15 (advanced kidney failure), sodium thiosulfate can accumulate and cause electrolyte shifts ^[3]. In this case, the drug is contraindicated unless your child is on hemodialysis, in which case it can be given on a dialysis day ^[6]. Always tell the oncologist if your child has kidney disease ^[9].

The retail pharmacy price for one 12.5 g infusion is approximately $255 ^[10]. Medicaid's NADAC (National Average Drug Acquisition Cost) benchmark is $2.36 per mL, which equals $118 for a 100 mL infusion—a 78% markup gap between retail and government pricing ^[10]. For a typical 4–8 cycle chemotherapy protocol, total retail cost is $1,020–$2,040; Medicaid cost is $472–$944 ^[10].

Insurance coverage is straightforward: if your child is receiving cisplatin chemotherapy, sodium thiosulfate is considered a medically necessary protective agent and is almost always covered at 100% ^[1][4]. Medicare, Medicaid, and commercial insurance all cover it because the FDA approved it specifically to prevent cisplatin-induced hearing loss ^[9]. There is no prior authorization delay in most cases because it is given during the same visit as chemotherapy ^[1].

Out-of-pocket cost depends on your insurance plan. If you have commercial insurance with a copay, it is typically $0–$50 per infusion ^[10]. If you are uninsured, ask the hospital's financial assistance office about charity care programs—most pediatric cancer centers have funds to cover sodium thiosulfate for uninsured families ^[1]. The cost is small compared to the $30,000+ lifetime cost of hearing aids and speech therapy ^[10].

Sodium thiosulfate does not interact with cisplatin in a way that reduces cisplatin's cancer-killing power ^[1][4]. In fact, the whole point is that sodium thiosulfate neutralizes cisplatin only in the bloodstream and tissues outside the cancer cells, allowing cisplatin to still enter and kill cancer cells ^[1]. Clinical trials confirmed that children who received sodium thiosulfate had the same cancer response rates as those who did not ^[4].

There are no reported interactions with other chemotherapy drugs like doxorubicin, etoposide, or carboplatin ^[9]. Sodium thiosulfate also does not interact with common supportive medications like anti-nausea drugs, antibiotics, or pain relievers ^[9]. It is safe to give alongside IV fluids, electrolyte replacements, and other standard chemotherapy support ^[1].

The only real interaction concern is kidney function. If your child is on dialysis or has severe kidney disease, sodium thiosulfate must be timed carefully to avoid electrolyte shifts ^[3][6]. Always tell the oncologist and nephrologist (kidney doctor) if your child has kidney disease, diabetes, or takes medications that affect kidney function ^[3].

When your doctor writes a prescription for Sodium Thiosulfate (RxNorm RxCUI 2618749, also dispensed under brand names including Pedmark), the goal is to target the root physiological pathway driving your condition rather than just masking surface symptoms ^[1]. According to the official FDA DailyMed package insert, 12.1 Mechanism of Action Cisplatin-induced ototoxicity is caused by irreversible damage to hair cells in the cochlea hypothesized to be due to a combination of reactive oxygen species (ROS) production and direct alkylation of DNA leading to cell death. Sodium thiosulfate interacts directly with cisplatin to produce an inactive platinum species. In addition, sodium thiosulfate can enter cells through the sodium sulfate cotransporter 2 and cause intracellular effects such as the increase in antioxidant glutathione levels and inhibition of intracellular oxidative stress. ^[2].

Across real-world patient logs on dotMD (79% positive worth-it rating), patients do best when they understand both what the medication is doing on day 1 and how long it takes to reach steady-state protection ^[3].

Most patients have no idea that the U.S. government publishes the exact wholesale invoice price that pharmacies pay for prescription drugs every week in the CMS National Average Drug Acquisition Cost (NADAC) database ^[1]. For Sodium Thiosulfate (RxNorm RxCUI 2618749), the federal acquisition benchmark is $2.3600 per unit ($70.80 for 30 units) ^[3].

Yet if you walk into a chain pharmacy without insurance—or with a high-deductible commercial plan—the register often quotes $255.00/month. By asking your pharmacist for their cash-match price or routing your prescription to a transparent cost-plus pharmacy (transparent generic mail-order pricing), you keep that markup in your own pocket ^[3][4].

One of the biggest reasons people quit a helpful medication in the first two weeks is starting at too high a dose too fast. In FDA DailyMed Section 2, Sodium Thiosulfate is available in 250 mg/mL Injection, Solution, 12.5 g/100mL Injection, Solution so your clinician can step your dose up gradually ^[2][5].

With an elimination half-life of Biphasic clearance with 5–17 hr terminal t½ under Sodium Thiosulfate maintenance, it takes roughly 4 to 5 half-lives for Sodium Thiosulfate to reach a steady plateau in your bloodstream. Never double up on a missed dose to "catch up"—if you miss a scheduled window, follow your package insert rules or call your pharmacist ^[5].

Clinical trial package inserts list every symptom that occurred during Phase 3 testing, which can feel overwhelming at 9:00 PM. When we cross-check FDA Adverse Event Reporting System (FAERS) data against real-world patient logs for Sodium Thiosulfate, the most practical day-to-day adjustments involve Nausea, Fatigue, Diarrhea, Headache ^[4][6].

Taking your dose at the consistent meal or bedtime window recommended by your pharmacist—and staying well hydrated—often cuts early adjustment symptoms significantly. However, if side effects persist past week 3, ask your doctor whether an extended-release formulation, a half-step dose reduction, or a class alternative makes sense ^[6].

Food, stomach acid, and common over-the-counter supplements can dramatically change how much Sodium Thiosulfate reaches your bloodstream. Divalent mineral cations like magnesium, calcium, iron, and zinc can bind directly to many oral medications in the gut, acting like a sponge that blocks absorption ^[5][7].

In addition, Sodium Thiosulfate undergoes specific hepatic and renal clearance pathways. Always tell your pharmacist about every supplement, NSAID, or grapefruit/herbal product you take ^[7].