The Science Of Addiction

To become addictive, a drug needs to be absorbed into the non-polar fatty lipid tissue of the brain (like substances dissolve like substances). This would mean that it would need to be a non-polar drug molecule with a -CH group at both ends (such as a methyl, ethyl, propyl, butyl, etc.) to be able to form London forces with the fatty lipid material and certain receptor cells of the brain.

For this reason aspirin is not likely to be addictive due to certain features in its molecular structure. Aspirin is a polar molecule with dipole-dipole attraction bonds and an -OH (hydroxyl) segment as part of a carboxylic acid group. This makes it easily dissoluble in other polar liquids, such as water (H2O) and blood plasma. Because of this, aspirin is not soluble in the non-polar fatty lipid material of the brain (like substances dissolve like substances) and therefore cannot bind to any particular receptors in the brain that deal with the pleasure sensation that can cause addiction, causing aspirin to have no psychoactive effect.