A few reports describe reduced
levothyroxine effects in patients given alum- inium/magnesium-containing
antacids. The
efficacy of
levothyroxine can also be reduced by the concurrent use of
calcium carbonate.
The general importance of the interaction with aluminium/magnesium - containing
antacids is not known, but be alert for the need to increase the
levothyroxine dosage in any patient given
antacids. With
calcium carbonate, the
mean reduction in the absorption of
levothyroxine is quite small, but some individuals can
experience a clinically important effect. The cautious approach would be to advise all patients to separate the dosages by at least 4 hours.