Alternative schedules of levothyroxine administration.

Abstract

Published evidence on bedtime versus prebreakfast administration of levothyroxine is reviewed. Because levothyroxine absorption has been shown to increase when the drug is administered to patients in a fasted state, the standard recommendation is that levothyroxine be taken one half to one hour prior to breakfast and at least four hours before or after potentially interacting drugs. However, compliance with this recommendation may be problematic for patients with unpredictable or variable schedules. A literature search identified four published studies of bedtime levothyroxine dosing. Two of the studies demonstrated a significant decrease in levels of thyroid-stimulating hormone (TSH) with levothyroxine administration at bedtime versus 30 minutes before breakfast, one study showed an increase in TSH when levothyroxine was taken at bedtime versus one hour before breakfast, and one study found no significant differences in TSH levels or other thyroid function monitoring limitations with bedtime versus standard dosing in subjects naive to levothyroxine therapy. The inconsistent study findings may be attributable to a number of variables, including dietary differences among the study populations, the use of potentially interacting supplements in one study, and variable intervals between levothyroxine administration and food intake. Neither dosing method correlated with substantial changes in assessments of quality of life or symptom severity; in two of the studies, patients indicated a preference for bedtime levothyroxine administration. Based on the available literature, bedtime administration of levothyroxine is an option for patients with hypothyroidism who want to avoid taking their medication with food.