title: Summertime dosage-dependent hypersensitivity to an angiotensin II receptor blocker.
abstract: BACKGROUND
  Summertime dips in blood pressure (BP), both in normotensive and hypertensive subjects, are well known. However, the dips are small and are not related to particular forms or doses of antihypertensive medication. Nevertheless it is the practice in some quarters to decrease antihypertensive medication in summer, and/or to increase in winter. Large scale studies being inconclusive, there are calls for long-term examination of the relationship between environmental temperature and blood pressure in single individuals under medication.
  
  
  METHODS
  While analyzing data from a subject whose BP had been controlled for a decade with the angiotensin-II receptor blocker losartan, an extreme, dosage-dependent, summertime dip came to light. Downward dosage adjustment appeared essential and may have prevented hypotension-related pathology.
  
  
  CONCLUSIONS
  The benefits of aggressive medication (the "J curve" phenomenon) being debated, the possibility of seasonal hypersensitivity, perhaps explicable in terms of differential signaling by countervailing receptors, should be taken into account when considering dosage adjustments in hypertensive subjects.
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, K7L3N6, Canada. forsdyke@queensu.ca.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Forsdyke
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000008:administration & dosage*; D000959:Antihypertensive Agents / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D054796:Drug Dosage Calculations; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology / Q000517:prevention & control; D019808:Losartan / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013696:Temperature; D013997:Time Factors
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000959:Antihypertensive Agents; D019808:Losartan