The use of "Catapres" in the treatment of severe hypertension

Evaluation of intravenous clonidine in hypertensive emergencies

Nineteen patients with severe essential hypertension or hypertension due to renal parenchymal disease were treated with intravenous clonidine. In 14 patients the elevated blood pressure was complicated by one or more crises: left ventricular failure in seven patients, encephalopathy in six, and subarachnoid hemorrhage, cerebral hemorrhage, dissecting aortic aneurysm, acute renal failure, and severe epistaxis, one episode each. Clonidine 0.15 or 0.30 mg, was given intravenously every 40 minutes until the diastolic blood pressure was decreased to 120 mm Hg or below. Blood pressure was taken every 10 minutes. Both systolic and diastolic blood pressure were reduced significantly after intravenous clonidine, the former by 96 mm Hg (P less than 0.001), the latter by 52 mm Hg (P less than 0.001) within a period of 40 minutes to 2 1/2 hours. The clonidine dose varied from 0.15 to 0.90 mg, mean 0.52 mg. Heart rate was decreased significantly by 20 beats/minute (P less than 0.001) by the drug. Serious side effects were not observed except for an episode of transient sinoatrial block. Renal function was not affected. Patients who were on chronic diuretic therapy prior to treatment with intravenous clonidine showed a significantly greater decrease in both systolic (P less than 0.01) and diastolic (P less than 0.001) blood pressure after the first clonidine dose. In one patient intravenous clonidine was not effective (i.e., blood pressure remained 200/150 mm Hg) in spite of a total clonidine dose of 0.9 mg. Two patients died, one from severe cerebral hemorrhage, the other from an extensive dissecting aortic aneurysm, but the fatal outcome was not related to clonidine.

A comparative trial of clonidine, propranolol and placebo in the treatment of moderate hypertension

1 A double-blind cross over trial between clonidine, propranolol and a placebo in patients with moderate hypertension has been performed. 2 Thirty-two patients completed the study which consisted of three treatment periods in random order of 3 months each. Patients had their blood pressure recorded by an unbiased observer using a random-zero machine. 3 Both clonidine and propranolol produced a significant reduction in blood pressure (P less than 0.01), which was apparent by the second week of therapy. Propranolol gave a greater reduction in pulse rate than clonidine (P less than 0.01) but clonidine also reduced the pulse rate significantly (P less than 0.05). There was no evidence of postural hypotension on either drug. Side-effects were more common with clonidine but these tended to wear off after several weeks of therapy. 4 Clonidine and propranolol were equipotent in reducing blood pressure, but clonidine has more initial side-effects than propranolol.

Treatment of severe hypertension and hypertensive emergencies with intravenous clonidine hydrochloride

Eleven severely hypertensive patients, median age 54 years, were treated with intravenous (i.v.) clonidine hydrochloride (Catapres). In nine there were life-threatening complications: severe left ventricular failure (LVF), hypertensive encephalopathy, cerebral haemorrhage, dissecting aortic aneurysm, renal failure, and severe epistaxis. In two patients there was pronounced, but uncomplicated, elevation of blood pressure. 0·15 mg or 0·3 mg clonidine was given every 40 min with electrocardiographic (ECG) monitoring. The mean systolic and diastolic blood pressures in the eleven patients were respectively 266 and 165 mmHg before treatment falling to 165 and 109 mmHg after treatment (P < 0·001). The mean decrease in heart rate was 26 beats/min (P < 0·001). Doses of clonidine required for control ranged from 0·15 mg (one ampoule) to 0·9 mg (mean 0·56 mg), although one patient received a total of 0·9 mg without an adequate response. The presenting condition caused the eventual death of two patients. There were no serious side effects, except for one transient episode of sino-atrial heart block. It is concluded that clonidine is effective and safe in the treatment of hypertensive emergencies.

Effects of clonidine withdrawal: possible mechanisms and suggestions for management

A severe rebound rise in blood pressure with agitation and insomnia had been noted in five patients when they had previously ceased clonidine (Catapres) This has been shown to be reproducible in these patients and to be associated with a significant increase in urinary catecholamine excretion. The blood pressure can be controlled and the symptoms alleviated promptly by alpha and beta adrenergic receptor blockade using intravenous phentolamine and propranolol.

Treatment of hypertension with clonidine

Clonidine, in a daily dosage of 0.15-4.8 mg., effectively lowered systolic and diastolic pressures in 26 out of 28 impatients with moderate to severe hypertension, including five with primary renal disease. The action of the drug did not depend on posture and was not associated with reduction in renal function. Side-effects were not severe, but mental changes occurred in four patients.Clonidine is a useful alternative to currently available antihypertensive drugs, but further evaluation of its longterm efficacy is required.