title: Cardiovascular withdrawal effects of clonidine and tiamenidine on abrupt cessation of oral treatment in conscious cats.
abstract: In conscious renal hypertensive cats prepared with permanent indwelling arterial catheters oral administration of clonidine (0.05 mg x 3 daily) clonidine (0.0125 mg x 3 daily), or tiamenidine (0.25 mg x 3 daily) induced hypotension and bradycardia during 6 days of treatment, although these responses were not well sustained. A pronounced tachycardia was demonstrated in all cats, 16-20 h after cessation of treatment with the higher dose of clonidine, however, only two cats in this group showed increased blood pressures above pre-dose levels at this time; these 'withdrawal' effects were absent 44 h after the final dose. No evidence of tachycardia, or blood pressure overshoot was seen up to 44 h after cessation of the low clonidine treatment regime, providing evidence for a dose-withdrawal effect relationship. Significant tachycardia was demonstrated in all cats 15-19 h after cessation of treatment with tiamenidine with no evidence of blood pressure elevation; the tachycardia was absent 48 h after the final dose. In four of these same cats clonidine (0.1 mg x 2 daily), in a long-acting, sustained release formulation (LA clonidine), elicited prolonged falls in blood pressure and heart rate over a 10 day period. No evidence of withdrawal effects were obtained 14-48 h after cessation of this treatment.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects*; D002415:Cats; D003000:Clonidine / Q000008:administration & dosage* / Q000627:therapeutic use; D003243:Consciousness; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008954:Models, Biological; D013375:Substance Withdrawal Syndrome; D013608:Tablets, Enteric-Coated; D013876:Thiophenes / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D000959:Antihypertensive Agents; D007093:Imidazoles; D013608:Tablets, Enteric-Coated; D013876:Thiophenes; C010354:tiamenidine; D003000:Clonidine