The risk of aluminum (Al) accumulation in patients with chronic renal failure has led to use of non-Al phosphate binders. Frequently, Al and non-Al phosphate binders are co-administered. Unfortunately, calcium citrate (Ca citr), when given with Al-gel, markedly enhances Al absorption. To determine whether calcium acetate (Ca acetate) also augments Al absorption, 10 normal volunteers were each given orally, three-day courses of the following drug combinations dosed four times daily: 1) aluminum hydroxide gel (Al[OH]3) (5 ml) alone; 2) Al[OH]3 (5 ml) plus Ca acetate (1330 mg); 3) Al[OH]3 (5 ml) plus Ca citr (950 mg). A nine day wash-out occurred between each course. Al levels were measured using flameless atomic absorption spectrophotometry. Daily urine Al excretion was measured during a two-day baseline before each course and during each three-day drug course. Plasma Al was obtained during each baseline and drug course. Mean 24-hour Al excretion (micrograms/g creatinine/day) at baseline versus treatment for each combination was: 1) 5.9 +/- 3.2 versus 42.0 +/- 40.7 (mean +/- SD); 2) 5.7 +/- 3.0 versus 40.3 +/- 28.6: 3) 6.3 +/- 3.4 versus 175.8 +/- 103.3. Al excretion was significantly greater with combination 3 than with either 1 or 2 (P less than 0.05). The difference between 1 and 2 was not significant. Plasma Al (micrograms/liter) at baseline versus treatment for each combination was: 1) 5.3 +/- 4.2 versus 8.1 +/- 2.5 (mean +/- SD); 2) 3.1 +/- 2.2 versus 7.3 +/- 2.9; 3) 3.0 +/- 2.3 versus 12.0 +/- 6.1.(ABSTRACT TRUNCATED AT 250 WORDS)