This will be an open label study of midazolam (dose 2 mg orally, Day 1) followed by midazolam (2 mg orally) given after dosing with intravenous F901318 4 mg/kg bid for one day followed by 2.5 mg/kg bid for 7 doses (Day 7). Up to twenty subjects will be included in two cohorts which will undergo the same dosing schedules of midazolam and F901318 and undergo the same procedures. The first cohort will consist of 12 subjects studied in two groups of six subjects each. If there is clearly a difference in midazolam kinetics detectable between the first and second doses of midazolam, in this first cohort, the second cohort will not be studied. If there is no clear difference, the second cohort will also be studied to give a final result. PK sampling for midazolam and 1- and 4-hydroxymidazolam plasma and urine concentrations will continue for up to and including 24 hours after dosing with midazolam on both occasions. PK sampling for F901318 will continue from before the first dose and up to 24 hours after the ninth dose. A follow up visit will be conducted 7 +/- 2 days after discharge from the clinical unit following completion of blood sampling following the second dose of midazolam and the ninth dose of F901318.