Adverse effects of antihistaminics

: Of most antihistamines more or less pronounced sedative effects are known. In recently developed substances this effect is said to be less or absent. After some days of application the sedative effect may decrease, but it can be enhanced by simultaneous intake of psychotropic drugs, sedatives or alcohol. There are important interindividual differences. The Drug Commission of the German Medical Profession (AKdA) received reports concerning tiredness, somnolence (even with new antihistamines), CNS-stimulation, nervousness, insomnia and paroniria have also been observed. Furthermore cases of dyskinesia have been reported, which are already described in the literature after long term intake, as well as anticholinergic reactions. Despite of their use as antiallergic drugs, reports on hypersensitivity reactions due to antihistamines, up to anaphylactic reaction have been not infrequently received by the AKdA. In rare cases disturbances of blood cell formation have been reported besides observations of gastrointestinal disorders, increase of appetite and weight. Abuse of antihistamine containing drugs was reported mainly for combinations with psychotropic agents.