Density functional theory calculations were carried out to study the effects of covalently binding isoniazid, an antitubercular compound to functionalized carbon nanotubes and fullerenes. Binding energies, energies of solvation, quantum-chemical molecular descriptors were calculated. Results from binding energies indicate that it is possible thermodynamically to covalently bind isoniazid to functionalized carbon nanotubes and to functionalized fullerenes, it being easier to bind isoniazid to functionalized fullerenes than to functionalized carbon nanotubes. From solvation energies calculations, it can be seen that the solubility of functionalized carbon nanotubes is higher than functionalized fullerenes, and both dissolutions in water are thermodynamically favorable. (c) 2007 Elsevier B.V. All rights reserved.