The interaction of the nimesulide molecule with pristine and Si-doped capped carbon nanotubes is studied by first-principle calculations. The nimesulide molecules, which are basic components of an anti-inflammatory drug, combined with carbon nanostructures, could result in novel drug delivery systems. In this Letter, the nimesulide interaction with pristine capped nanotubes is shown as occuring in a physisorption regime and it is demonstrated that this interaction can be much more intense when the capped nanotube is substitutionaly doped with an Si atom. Then, the Si-doped capped nanotube can constitute a feasible novel nimesulide molecule delivery system. (C) 2007 Elsevier B.V. All rights reserved.