[H1 antihistaminics: can we precisely define the characteristics of the ideal molecule?]

The experience of the past twenty years in the field of H1 antihistamines prompts us to consider that these drugs are more dissimilar than has previously been reported in the scientific literature. In fact, the H1 antihistamines that are used in man seem to be effective, even if there are some differences in clinical efficacy. Nevertheless they may have marked differences as far as the following aspects are concerned: their possible binding to various biological targets, their pharmacokinetics, their metabolism and their volume of distribution. All these differences must be taken into consideration when judging the real quality of each of these drugs.