Effect of levothyroxine administration time on serum TSH in elderly patients

BACKGROUND: Standard drug information resources recommend that levothyroxine be taken on an empty stomach due to the potential for interaction with food or medications. Due to concern about unpredictable response to levothyroxine in patients receiving morning doses in a skilled nursing facility, the standard administration time for the drug was changed from 0900 to midnight. OBJECTIVE: To determine if a change in response to levothyroxine as determined by the serum ultrasensitive thyroid-stimulating hormone (TSH) concentration occurred when the time of administration was changed from early morning to midnight. DESIGN: Retrospective chart review. SETTING: A 187-bed skilled nursing facility. PARTICIPANTS: Fifteen nursing home residents receiving levothyroxine during the change of administration time with a mean age of 84 years met inclusion criteria, with at least one TSH concentration reported prior to and at least one serum TSH concentration reported after the change in administration time to mignight. MEASUREMENTS: Serum TSH concentrations. RESULTS: There was a decrease in serum TSH of 0.286 +/- 1.722 mU/mL (mean +/- SD) after changing the administration time to midnight that was not statistically significant (t = 0.643; p = 0.532). CONCLUSIONS: Based on the results of the study, we conclude that levothyroxine could be routinely administered after breakfast.