Is it possible to use the ADG1419 with +5V / -18V supplies?
This is outside the +/-16.5V range listed in the +/-15V operation section, but well inside the 25V GND to VSS rating and the 35V VDD to VSS rating.
Unfortunately we cannot guarantee the operation of this device at these supply ranges as it is outside the range specified in the datasheet.
The absolute max ratings on the datasheet are stress rating and do not indicate performance.
You could have a look at the ADG5436F. This is a Dual 2:1 that operates from +/-5 V to +/-22 V dual supply.