The proposed use of nanocapsules in drug delivery systems promises many advantages over current procedures. The major advantage is the potential for patients to have significantly reduced side effects from taking the drug, especially for highly toxic drugs such as those used for cancer treatments. Nanotubes have been suggested as one such carrier to deliver a drug to a specific site, giving rise to the notion of the 'magic bullet'. The aim of this paper is to determine whether a particular nanotube would accept a particular drug, and to determine the radius of the nanotube that provides the maximum uptake of the drug molecule. In particular, this paper looks at the drug cisplatin, a platinum based anticancer drug widely used in the treatment of tumours. Three orientations of cisplatin, a polar molecule, are investigated as it enters the nanotube. It is shown that, for all three orientations of cisplatin to be accepted into the carbon nanotube, the minimum radius must be at least 4.785 Å, which is slightly smaller than a (9, 5) nanotube and that the maximum suction energy occurs when the carbon nanotube radius is approximately 5.3 Å, which is approximately equivalent to a (11, 4) nanotube. This paper presents for the first time a calculation of this nature, and although the model represents only a first approximation, it constitutes a necessary preliminary calculation which might provide medical scientists with some overall guidelines.