title: Effects of abrupt cessation of treatment with clonidine and guanfacine on blood pressure and heart rate in spontaneously hypertensive rats.
abstract: Present experiments were undertaken to compare the effects of clonidine and guanfacine withdrawal on blood pressure in spontaneously hypertensive rats. Five week oral administration of clonidine at a dose of approximately 300 microgram/kg/day produced a significant hypotension. After acute interruption of clonidine administration, a marked blood pressure rise was observed. Peak blood pressure rise was reached within 24 hours after clonidine withdrawal. A significant increase in plasma norepinephrine concentration was observed when clonidine treatment was discontinued. On the other hand, long-term administration of guanfacine at a dose of approximately 3 mg/kg/day produced a significant hypotension. After a five week administration of guanfacine, abrupt cessation did not produce a rapid blood pressure rise. Catecholamine concentration in urine and plasma was not influenced either by guanfacine administration or its withdrawal.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D003000:Clonidine / Q000627:therapeutic use*; D004837:Epinephrine / Q000097:blood; D016316:Guanfacine; D006146:Guanidines / Q000627:therapeutic use*; D006339:Heart Rate; D006973:Hypertension / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010648:Phenylacetates / Q000627:therapeutic use*; D051381:Rats
chemical_list: D006146:Guanidines; D010648:Phenylacetates; D016316:Guanfacine; D003000:Clonidine; D009638:Norepinephrine; D004837:Epinephrine