the excretion of gemfibrozil

1)what is the way of excretion of gemfibrozil is it by urine or feces including percentage
2) what is the plasma level of the drug
including numbers of that with the best dose
3)what is the toxcity level of the drug
4)what is the test that shows(egfr) the kidney function and how the drug effect it function and when should be avoided