Coated tablets of (6-(5-chloro-2-pyridyl)-5-[(4-methyl-1-piperazinyl)carbonyloxy]-7-oxo-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazine) are provided. The tablets minimize the perceived bitterness of the medicament. A method for analyzing instantaneous dissolution of sub-microgram quantities of core material is also disclosed.