Pharmacokinetics of potassium chloride in wax-based and syrup formulations

The effect on plasma potassium of 64 mmol potassium chloride (KCl) in two oral formulations was compared against placebo in five healthy men, and their bioavailability was calculated from urinary data. Mean plasma potassium varied between 4.0-4.6 mmol/l during the placebo phase and mean (s.d.) urinary potassium excretion was 84.4 (18.5) mmol over 36 h. KCl syrup produced a significant change in plasma potassium over 24 h (P less than 0.02) with a marked elevation in the first 3 h after dosing and a mean (s.d.) peak plasma potassium 1.72 (0.52) mmol/l higher than placebo (P less than 0.05). By 36 h an excess of 55.9 (23.9) mmol potassium, equivalent to 87.3% of the stated dose, was excreted in the urine. KCl in wax base had a less consistent effect on plasma potassium (P greater than 0.5) and its effect was no more prolonged. The mean peak increment in plasma potassium was 1.03 (0.42) mmol/l (P less than 0.01) and the total potassium excretion was 50.5 (17.7) mmol higher than placebo values giving a bioavailability of 78.8% calculated from the stated dose.