MC34063 help - step-up with an external switch
When designing a boost converter, you can choose a switched inductor (aka flyback or switched boost) for reasonable size inductors up to 100W or a feedforward boost regulator with a stepup transformer and opto or tertiary winding feedback.

You must consider for any type that the voltage ratio is linear while the impedance ratio is squared so your source drivers must be &lt;5% of the load Z referred back to source for high efficiency.

Voltage ratio of 200/5 = 40 implies an impedance ratio of 1600 @5V so a rated load of 200V/10mA=20K appears as 20k/1600=12 Ohm load to 5V source thus 5% of this is 600 mOhm while your part is 1.8 Ohm which dissipates 3x what I recommend for switch losses and a good size little heat is needed. 

So the higher the input voltage, the lower the switch losses from input V*I. or a lower RdsOn SMD switch.

A flyback design can be considered suitable here or a feed forward step up transformer. There are many choices,  but keep in mind the impedance ratios and input referred switch losses.