Sample preparation for UV analysis of drug content in capsules/tablets
I'd agree with Zhe that "this is a non trivial problem." Method development is tricky if you don't have a standard analysis procedure. 

When you dissolve the capsule, if you do have suspended particles then yes they will interfere with the UV analysis. So do centrifuge. 

But think of the removal of the liquid as an extraction. So add more solvent to the centrifuge tube, shake up the particles and centrifuge again. Assuming that you won't over dilute, I'd do the extraction three times, then dilute to the final volume. 

The rub here in my mind is that UV is not very selective. I'd doubt that you're going to get a nice flat baseline with one nice peak. So you'll need a "pure" drug sample to compare to your extract samples to see if there is any other gunk causing interference.