We have studied the pharmacokinetics of
amiloride and its analogs. A high-performance liquid chromatographic method has been adapted for the measurement of
amiloride,
5-(N-ethyl-N-isopropyl)amiloride (
EIPA) and 5-(N, N-hexamethylene)amiloride (HMA) in mouse plasma, kidney, liver and
tumor tissues. The method uses a C8 preparative solid-phase column, followed by separation using a reversed-phase C18 column (250 x 4 mm I.D., 5 microns particle size) with detection by ultraviolet absorption at 365 nm. Reversed-phase separations were performed at ambient temperature using a non-linear gradient method with two different mobile phases: mobile phase A was 100%
acetonitrile while mobile phase B was 0.15 M
perchloric acid at pH 2.20 (flow-rate was 1.2 ml/min). The retention times for
amiloride,
benzamil (used as an internal standard),
EIPA and HMA are 13.4, 19.5, 21.8 and 23.5 min, respectively. The calibration curves are linear over the range of 0.1-50 microM in plasma and in tissues. The half-lives of
amiloride,
EIPA and HMA (and their confidence intervals) in plasma after
intraperitoneal injection of drugs into mice were 68.8 +/- 0.2, 31.2 +/- 2.5 and 39.3 +/- 7.9 min, respectively.
Amiloride was detected as a metabolite of
EIPA but not of HMA. When
EIPA was injected at a dose of 10 micrograms/g
body weight, it was cleared rapidly from liver, but concentrations > 1 microM were sustained for at least 2 h in murine kidney and in a transplantable
tumor.