title: Urinary N-methylhistamine in asthmatic children receiving azelastine hydrochloride.
abstract: BACKGROUND
  Histamine has a particular role in the pathogenesis of bronchial asthma, and many antiallergic drugs have been developed with antihistaminic action in mind. Recently, a sensitive and specific assay for measuring histamine and its metabolites has been developed. There are, however, no reports of the effect of antiallergic drugs on histamine levels in asthmatic patients.
  
  
  OBJECTIVE
  To determine the relationship between clinical symptoms and histamine levels in asthmatic patients receiving an antiallergic agent.
  
  
  METHODS
  A prospective study was designed in asthmatic children treated with azelastine hydrochloride. The evaluation of clinical symptoms was based on scores of the severity of exacerbations, activities of daily living, quality of sleep, and required therapy. Urinary excretion of N-methylhistamine, a major metabolite of histamine, was measured by double antibody radioimmunoassay.
  
  
  RESULTS
  In the patients treated with azelastine, the improvement in clinical symptoms of bronchial asthma correlated significantly with a decrease in urinary N-methylhistamine excretion (r2 = 0.434, P < .001), while no such relationship was noted in patients receiving no antiallergic agent. Urinary N-methylhistamine excretion showed no diurnal change or influence of meals.
  
  
  CONCLUSIONS
  Decreased urinary N-methylhistamine excretion may be a direct reflection of the antihistaminic action of azelastine in vivo. Measurement of urinary N-methylhistamine excretion can be used to evaluate the efficacy of agents with antihistaminic action in the treatment of bronchial asthma.
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Kagoshima University, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Takei
authors.forename: A
authors.initials: A
authors.lastname: Shimago
authors.forename: M
authors.initials: M
authors.lastname: Iwashita
authors.forename: T
authors.initials: T
authors.lastname: Kumamoto
authors.forename: K
authors.initials: K
authors.lastname: Kamuro
authors.forename: K
authors.initials: K
authors.lastname: Miyata
mesh_terms: D018926:Anti-Allergic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001249:Asthma / Q000188:drug therapy* / Q000652:urine*; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm; D004305:Dose-Response Relationship, Drug; D005260:Female; D006633:Histamine Antagonists / Q000627:therapeutic use*; D006801:Humans; D007223:Infant; D008297:Male; D008761:Methylhistamines / Q000652:urine*; D010793:Phthalazines / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D018926:Anti-Allergic Agents; D006633:Histamine Antagonists; D008761:Methylhistamines; D010793:Phthalazines; C048140:N-methylhistamine; C020976:azelastine