Is the bioavailability of famotidine reduced by an antacid?

Famotidine is a potent histamine H2-receptor now undergoing clinical trial in Italy, Germany, the UK, France, and the USA, and has just come on the market in Japan. To study the effect of concurrent antacid administration on the oral absorption of famotidine, 10 subjects (8 patients with peptic ulcer, 2 normal adults) received 20 mg (5 subjects) or 40 mg (5 subjects) of famotidine with and without Maalox (aluminum hydroxide and magnesium hydroxide). Slight declines in the maximum plasma concentration and the areas under the plasma concentration time curve of famotidine were observed when an antacid was given simultaneously, indicating that concurrent antacid decreases the bioavailability of this new antisecretory compound. Although the plasma famotidine level was lowered by concurrent administration of antacid, it remained higher than the plasma concentration for 50% inhibition of stimulated acid secretion (IC50) for up to 12 hours.