The elimination half-life of estromustine with oral EMP was 13.6 hours on average, with a range of 8.8 to 22.7 hours. Conversely, the elimination half-life of estromustine with intravenous injection was 10.3 hours, with a range of 7.36 to 12.3 hours. For comparison, the corresponding elimination half-lives of estrone were 16.5 and 14.7 hours for oral and intravenous administration, respectively. Estramustine and estromustine are mainly excreted in bile and hence in feces. They are not believed to be excreted in urine.