TO THE EDITOR:
In a recent article (1), the first sentence starts “Ciprofloxacin labeled with 99mTc… .” This phrase is repeated throughout the article. This statement is internally contradictory. Ciprofloxacin contains only the elements carbon, hydrogen, fluorine, nitrogen, and oxygen. It does not contain technetium. Ciprofloxacin can be labeled with radionuclides of only these 5 elements. Pertechnetate apparently forms a stable complex with ciprofloxacin under reducing conditions, but this product is not technetium-labeled ciprofloxacin. It is a new compound with a unique set of chemical and biologic properties that may or may not be similar, but will not be identical, to ciprofloxacin. Similarly, the name 99mTc-ciprofloxacin implies that the technetium isotope or isotopes normally present in ciprofloxacin have been replaced with 99mTc. 18F-Ciprofloxacin and 14C-ciprofloxacin are viable names for suitably labeled versions of the compound, but 99mTc-ciprofloxacin is not. The same logic applies to 99mTc-enrofloxacin.
This may seem like semantic pedantry harping on arcane rules of chemical nomenclature, but it is in fact central to our discipline. Reproducible experiments can be performed using labeled compounds only if we know what that labeled compound is. It is critical to distinguish between labeled compounds and labeled derivatives of compounds. Naming conventions have developed over the years so that a systematic name will exactly describe the compound to which it is applied. This often leads to cumbersome names—indeed, the systematic name for ciprofloxacin is 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quino-linecarboxylic acid—that have to be shortened or trivialized for routine usage. However, these trivial names are tied to the systematic name, and variations on the trivial name should still follow systematic rules. Thus, we have 131I-iodinated albumin, not 131I-albumin. Variations, induced by usage, are inevitable, but variations that are internally contradictory should be avoided at all costs. Such internally contradictory names serve only to confuse both the reader and indexing systems.
Until the structure of these compounds has been determined, they should be described as 99mTc complexes of ciprofloxacin or enrofloxacin. When the structure of the complexes is known it will be possible to assign a meaningful name to the compounds.
