Ignore the second post by EdStreet and use the link he posted in his first message where you can see the important footnotes that are left off in the second message.
Specifically "reduce speed when drilling end grain". Most wood pen blanks (but not all) will be drilled end grain.
The recommended speeds (for acrylic) look way too high to me for resin pen blanks where you are drilling a deep hole. ~500 rpm should be plenty given the likely feed rate (which for pen makers (especially drilling on the lathe) is likely slower than what is assumed in the posted chart). Too high an rpm will just heat up the bit and the blank creating problems. That's my thinking anyway.
Another thing to consider is that if you are using carbon steel (common in cheap forstner bits), they will not tolerate much heat at all. HSS bits can take a lot more heat punishment, but that doesn't mean your material will.
Ed