Levothyroxine sodium is available in 100-, 200-, and 500-mcg vials.2883 Also present in the vials are dibasic sodium phosphate heptahydrate, mannitol, and sodium hydroxide.2883 The contents of each vial should be reconstituted by adding 5 mL of sodium chloride 0.9%, resulting in solutions containing levothyroxine sodium 20, 40, and 100 mcg/mL, respectively.2883 Shake well to ensure complete dissolution.2883
Levothyroxine sodium injection may be administered undiluted by intravenous injection.2883 The drug also has been administered by intramuscular injection,2885 however the current labeling no longer includes this information.2883
Intact vials should be stored at controlled room temperature and protected from light.2883 After reconstitution, the drug is stable for 4 hours; however, the manufacturer states that the drug should be used immediately.2883 Vials are intended for single-use only; unused portions should be discarded.2883 The manufacturer also states that levothyroxine sodium injection should not be added to intravenous solutions.2883
Syringes
Levothyroxine sodium 0.1 mg/mL in sodium chloride 0.9% was packaged as 5 mL in 6-mL polypropylene syringes (Monoject). No loss of drug was found after 7 days at 5°C.2354
Sorption
In a study of levothyroxine sodium stability in glass, polyolefin, and PVC containers for continuous infusion, delivery of the drug through PVC tubing resulted in 13% loss of drug in glass and polyolefin containers and 18% loss of drug in PVC containers over 1 hour as a result of sorption to the PVC materials.2884 Levothyroxine sodium concentrations returned to greater than 90% of the initial concentration by 3 hours in all 3 container types and thereafter remained above 90% for the duration of the 24-hour study period.2884 The use of polyolefin tubing or flushing of a PVC line with levothyroxine solution prior to administration has been suggested to minimize such sorption.2884
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