In-use stability of diluted thiamazole (methimazole) infusion solutions in prefilled 0.9% sodium chloride infusion bags for continuous infusion.

OBJECTIVE

In patients with severe hyperthyroidism unable to tolerate oral antithyroid therapy, diluted thiamazole infusion solutions (dose 120-240 mg) are administered by continuous infusion over 24 hours. Information about the type of diluent and compatibility/stability of the ready-to-administer thiamazole preparation is missing in the summary of product characteristics of the injection concentrate marketed in Germany. We studied the in-use stability of diluted infusion solutions over 24 hours.

METHODS

Thiamazol 40 mg inject. Henning was diluted in prefilled polyolefin infusion bags containing 250 mL 0.9% sodium chloride (NaCl) infusion solution and kept for 24 hours at room temperature and diffuse room light. Content of the diluted infusion solutions (0.48 and 0.96 mg/mL) was analysed every 4 hours over the course of 24 hours by reversed-phase high-performance liquid chromatography. pH was measured after 0, 12 and 24 hours. The infusion bags were regularly inspected for visible particles. Subvisible particles were measured by particle counting.

RESULTS

Thiamazole infusion solutions of the nominal concentrations 0.48 and 0.96 mg/mL in 0.9% NaCl diluent, kept at room temperature under diffuse room light, are physicochemically stable over a period of at least 24 hours. No evidence of colour change, particle formation or pH change was observed throughout the observation period.

CONCLUSION

Dilution of 120 or 240 mg doses of licensed thiamazole injection concentrate with 0.9% NaCl infusion solution in prefilled polyolefin containers is recommendable for continuous infusion over 24 hours in the treatment of thyrotoxicosis.