The relative bioavailability of enteric-coated sodium fluoride (NaF) tablets (10 mg F-) has been assessed following administration with a standard calcium-rich breakfast or calcium-poor lunch, and 2 h before or simultaneously with antacid administration (2.4 g aluminum-magnesium hydroxide), versus intake on an empty stomach. Twelve volunteers were studied 3 times according to an open, three-way crossover design over a 24 h period at weekly intervals. Meals were found to decrease the peak serum concentration of NaF from 122 micrograms/L during fasting (after baseline subtraction) to 71 and 88 micrograms/L with breakfast and lunch respectively, and to slow its absorption rate with Tmax increasing from 3.3 to 7.3 and 11.2 hours, without altering its bioavailability. Antacid impaired the bioavailability of NaF by 80% when administered simultaneously, with AUC decreasing from 987 to 155 micrograms.h/L, but had no significant effect when taken 2 h before NaF. In conclusion, the enteric-coated NaF tablets used in this study can be administered with food or after a 2-hour delay following antacid administration, but should not be taken simultaneously with antacid.