title: Dynamic and biochemical responses to single and repeated doses of clonidine during dynamic physical activity.
abstract: Beta-adrenoceptor blockade increases serum K, which may be related to renin inhibition, hypoaldosteronism, and exercise-induced skeletal muscle release of serum K. We report on the dynamic and biochemical response to clonidine (C) after single (S) 0.2-mg and repeated (R) 0.1-mg bid doses of C to six normal subjects at rest, 2 hr after dosing and immediately before dynamic physical activity (DPA) on a treadmill, and at peak activity and 2 hr after DPA. Blood pressure (BP), heart rate (HR), plasma renin concentration (PRC), aldosterone (ALD), serum K, epinephrine (E), and norepinephrine (NE) were measured in standing subjects before and 2 hr after placebo or C (S or R), at peak DPA, and 2 hr after exercise. K, BP, and HR were also determined during all stages of DPA. Results show a parallel rise in K at peak over rest after C (S or R) and after placebo. NE, E, and PRC decreased after 1 wk of C (P less than 0.01), but the fall of ALD was only slight. The fall in NE at rest suggested a relationship to the decrease in systolic BP and rate pressure product after 1 wk on C. With DPA there is a normal yet smaller increase in systolic BP and also a smaller rise in HR with S- and R-dose C. There is no adverse rise in K in C-treated subjects during DPA.
mesh_terms: D000450:Aldosterone / Q000097:blood; D003000:Clonidine / Q000494:pharmacology*; D004837:Epinephrine / Q000097:blood; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D009638:Norepinephrine / Q000097:blood; D005082:Physical Exertion; D011188:Potassium / Q000097:blood*; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000187:drug effects*
chemical_list: D000450:Aldosterone; D012083:Renin; D003000:Clonidine; D011188:Potassium; D009638:Norepinephrine; D004837:Epinephrine