ABSORPTION, METABOLISM AND DISTRIBUTION OF [14C]‐O‐METHYLDOPA AND [14C]‐l‐DOPA AFTER ORAL ADMINISTRATION TO RATS

1 The absorption, tissue distribution, and metabolism of [14C]‐O‐methyldopa were compared with those of [14C]‐l‐DOPA after oral administration to rats. 2 Total radioactivity in the plasma and brain of rats treated with [14C]‐O‐methyldopa was significantly higher (2 fold and 30–50 fold, respectively) than that of rats treated with [14C]‐l‐DOPA. 3 Total radioactivity in the gut washings and intestinal tissue 2 h after oral administration was significantly higher in rats treated with [14C]‐l‐DOPA than in rats treated with [14C]‐O‐methyldopa. The reverse was observed in the stomach tissues. 4 Peripheral metabolism of [14C]‐O‐methyldopa was much lower than that of [14C]‐l‐DOPA; the major metabolite of [14C]‐O‐methyldopa in the plasma is l‐DOPA, whereas l‐DOPA is mainly metabolized to phenylcarboxylic acids.

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