antihistamines: psychomotor performance and driving H1 antihistamines: psychomotor performance and driving

As has already been extensively commented in the article on antihistamines and the central nervous system, published in this same issue, all the classical antihistamines and, to a lesser extent, the more recent synthetic compounds are able to exert depressive action upon the central nervous system (CNS), causing drowsiness, lassitude, dizziness, incoordination, and increased reaction time. Moreover, in many cases they also induce peripheral neurological effects secondary to cholinergic block (dilatation of the pupils, blurry vision, or dry mouth), which can affect patient ability to drive. According to information from the traffi c authorities, in Spain each year motor vehicle accidents cause 5000 deaths and 130,000 injuries – the majority affecting people under 40 years of age. At least one-third of these accidents are due to human factors related with the driver, including alcohol consumption, risk behavior and, in some cases, drug substances [1]. In 2004 the Comisión Profesional de Sociedades Sanitarias para la Prevención de Lesiones por Accidentes de Tráfi co (COSPLAT) was created, comprising 38 medical societies, including the Sociedad Española de Alergología e Inmunología Clínica (SEAIC). The joint objectives of the SEAIC and COSPLAT include the elaboration of a list of antiallergic medicines, the use of which should be limited among drivers, and the recommendations of the medical community regarding the prescription of other, safer alternatives [2]. Patients treated with antihistamines are largely outpatients, and so therefore also habitual drivers. As has also been extensively documented in other articles of this same issue, all the fi rst generation antihistamines, and many of the second generation drugs (ketotifen, loratadine, ebastine, mizolastine, rupatadine), undergo total or partial liver metabolization through isoenzymes of the cytochrome P450 system (CYP3A4, CYP2D6). In addition, to one degree or other, they interact with alcohol (reinforcement of sedative effects) and with other drugs that make use of the same metabolic pathways (macrolides, imidazoles, H2 antihistamines, serotonin reuptake inhibitors), thus giving rise to unpredictable increases in the plasma levels of the antihistamine, and to prolonged elimination rates [3]. All this must be taken into account when antihistamines are used by habitual drivers, and particularly by professional drivers.