Plasma clearance of neostigmine and pyridostigmine in rats with ligated renal pedicles

The elimination of equimolar doses of ¹⁴C-neostigmine and ¹⁴C-pyridostigmine was studied in rats with ligated renal pedicles. Although both drugs were eliminated from plasma in a bi-exponential manner, there were statistically significant differences in their plasma half-lives. It was considered that this phenomenon might be related to qualitative differences in hepatic metabolism. The results of the experiments suggest that the metabolism of pyridostigmine is slower than neostigmine and that cumulation of pyridostigmine may occur in renal failure.