Phenofibric acid T 1/2 is between 10 and 35 hours. The removal of most phenofibrate is done by 60 percent by the kidneys. 25 percent of the drug is removed with feces. Gemfibrozil is well absorbed from the gastrointestinal tract. Metabolized in the liver. T 1/2 Approximately 1.5 hours, up to 70 percent of the drug is excreted unchanged through the kidneys, 6 percent is removed with feces. Nicotinic acid preparations contain nicotinic acid and tablets in extended-release form. delayed release crystals