Br. J. clin. Pharmac. (1981), 1, 73-77 CHANGES IN BLOOD PRESSURE, PLASMA CATECHOLAMINES AND PLASMA RENIN ACTIVITY DURING AND AFTER TREATMENT WITH TIAMENIDINE AND CLONIDINE B.G. HANSSON Department of Medicine, County Hospital, S - 30185 Halmstad, Sweden B. HOKFELT Department of Endocrinology, University of Lund, Malmo General Hospital, S - 21401 Malmo, Sweden 1 Tiamenidine (Hoe 440) is an imidazoline with blood pressure lowering properties. Its pharma- cology resembles that of clonidine. 2 The effect ofboth drugs on blood pressure, plasma noradrenaline (NA), plasma adrenaline (Ad), urinary catecholamines and plasma renin activity (PRA) was assessed in four previously untreated male hypertensive patients in a cross over study. 3 The maximum daily dose of tiamenidine was 3 mg. The maximum daily dose of clonidine was 450,ug. 4 During treatment, blood pressure, systolic and diastolic, supine and erect, fell on average between 12 and 15%. Levels of NA, Ad, PRA were reduced during treatment. 5 During withdrawal of either drug there was rebound of blood pressure and NA, Ad, PRA, overshooting baseline levels. 6 The withdrawal effects caused by clonidine were similar for tiamenidine. Introduction Tiamenidine is an imidazoline derivative which receptors inhibitory to sympathetic nerve activity. It lowers blood pressure and its pharmacology is an effective hypotensive which does not signifi- resembles that of clonidine. In cat, dog and rabbit, cantly modify homeostatic cardiovascular reflexes. single doses intravenously produce an initial rise in It is now well documented that the cessation of blood pressure followed by a sustained fall (Lindner clonidine therapy may be associated with withdrawal & Kaiser, 1974). In dogs, oral administration pro- phenomena, of which the clinically most serious is a duces a sustained hypotensive effect. Injection into rise in blood pressure which may overshoot pre- CSF in dog, or lateral ventricle in rat, produces a dose treatment levels. This is usually accompanied by a rise related fall in blood pressure not preceded by a tran- in plasma catecholamine levels and plasma renin sient elevation (Schoelkens & Lindner, 1977). In activity. The implications of the phenomena are renal and genetic hypertensive rats tiamenidine also potentially serious for the patient who does not reli- produces a dose dependent fall in blood pressure. In ably take his tablets orwho abruptly stops treatment. this species it also inhibits plasma renin activity Preliminary results in hypertensive rats suggested (Lindner & Schoelkens, 1977). that following 14 days treatment with equihypoten- In man tiamenidine produces a substantial hypo- sive doses, withdrawal of medication resulted in an tensive effect in the dose range 1-3 mg per day. Blood increase in catecholamines which was approximately pressure and heart rate changes in response to tilt are half as great with tiamenidine as that in a control only minimally modified by tiamenidine. It induces group of rats who received clonidine (Ellis, Novick & a marginally decreased response to the cold pressor Wilker, 1979). test, and a very small reduction in response to The present study was designed to quantify the Valsalva's manoevre. hypotensive effect of both tiamenidine and clonidine, Therefore like clonidine it possesses a transient to determine their effect on plasma and urinary cate- peripheral a-adrenergic receptor stimulant effect and cholamine levels and on plasma renin activity and to a dominant central effect exerted through adrenergic determine the effects of withdrawing therapy, if any. 0306-5251/81/010073-05 $1.00 (C) Macmillan Publishers Ltd 1981 74 B.G. HANSSON & B. HOKFELT Methods Plasma catecholamines Selection ofpatients These were measured daily at 8.00 h (supine) and 12.00 h (erect) during hospitalisation, using a double Newly diagnosed patients with primary essential isotope technique (Engleman & Portnoy, 1970). moderate hypertension (WHO Grade 2) were eligible to participate in the study if they were aged between Plasma renin activity 20 and 65 years, male, intellectuably able to comply with the study and suitable for outpatient therapy. This was measured daily during hospitalisation at 8.00 They could not participate if they had severe con- h (supine) and 12.00 h (erect) using the method des- comitant renal, cardiovascular or cerebrovascular cribed by Haber, Koerner, Page, Kliman & Pemode complications or severe intercurrent illness, or were (1969). receiving sedatives, tranquillisers, antidepressants, cardiac glycosides or diuretics prior to the start of the Weight study. The protocol was reviewed by the ethical com- mittee of the medical faculty Lund University, and This was measured daily before breakfast during informed consent to participate was sought from hospitalisation. eligible patients. The medical history and physical examination, ECG, chest X-ray, ophthalmological examination Procedure and routine laboratory tests were also performed on each patient. In this cross over study the participants were admitted to hospital for the clinical and laboratory investiga- tions outlined below. The baseline data was obtained Results over a 3 day period after which the patients were allocated to treatment with tiamenidine or clonidine Treatment with either drug produced a hypotensive according to a random code. Treatment began in effect even on the first day. On the last day of treat- hospital, but after 2 days was continued on an out- ment the mean of the daily blood pressure readings patient basis for 4 to 6 weeks. The dose was titrated for both drugs was remarkably similar (Tables la during this time between the ranges 450 ,ug-900 ,ug, and lb). (Systolic and diastolic pressures were clonidine, and 1.5 mg-3.0 mg, tiamenidine, to pro- reduced by almost 15%). The withdrawal pheno- duce an optimum effect. mena attributable to both drugs can therefore be After the first treatment period, the patients were interpreted fairly in the context of their equihypo- readmitted to hospital and the effects of the treat- tensive activity. ment were measured over 2 days. The effects ofwith- The patients did not respond equally to cessation of drawal were measured over the next 3 days and the therapy, but all patients showed some overshoot of second treatment then introduced. The programme mean daily blood pressure above baseline values at was repeated. some time in the three days after withdrawal. The mean daily blood pressure of the patient most sensi- tive to withdrawal exceeded mean baseline daily Blood pressure blood pressure by up to 29 mm Hg systolic and 16 mm Hg diastolic. The supine pressure was always assessed first, after The patient whose blood pressure was most sensi- 30 min recumbency, and measured three times at tive to clonidine withdrawal was also most sensitive to 1 min intervals. After 3 min in the erect position the tiamenidine withdrawal. Similarly the least affected pressure was at 1 again assessed three times min by clonidine withdrawal was also least affected by intervals. The diastolic pressure was recorded when tiamenidine withdrawal. the sounds disappeared (Korotkoff V). The record- Plasma noradrenaline was measured in supine and ings were always made in the same dominant arm. upright positions. The pattern of change was similar During hospitalization measurements were made at for both amines with both drugs. Levels were lower 8.00, 10.00, 12.00, 14.00, 16.00, 18.00 and 20.00 h on the last day of treatment than during the control every day. period, and rose successively on the three post treat- ment days (Table 2), with some overshoot ofbaseline Urine catecholamines (24 h) levels. Changes in plasma adrenaline levels in the supine These were measured each day during hospitalisation position followed a similar pattern, but in the upright according to the method described by von Euler & position there was no consistent change after with- Lishajko (1961). drawal of treatment (Table 3). WITHDRAWAL OF TIAMENIDINE AND CLONIDINE 75 Table 1 a) Mean daily blood pressure variation before, during and after therapy in the supine position Treatment Tiamenidine Clonidine Bloodpressure (mmHg) Systolic Diastolic Systolic Diastolic Mean Range Mean Range Mean Range Mean Range Baseline 160 159-163 110 97-115 160 159-163 110 97-115 Treatment first day 143 137-151 102 96-108 135 127-142 93 90-95 Treatment last day 140 135-145 95 90-100 140 129-145 94 88-99 Withdrawal day 1 161 153-171 106 97-120 150 127-158 99 95-106 Withdrawal day 2 168 156-187 112 100-130 165 145-179 108 97-122 Withdrawal day 3 166 152-183 113 105-129 171 154-179 113 102-127 b) Mean daily blood pressure variation before, during and after therapy in the upright position Tiamenidine Clonidine Blood pressure (mmHg) Systolic Diastolic Systolic Diastolic Mean Range Mean Range Mean Range Mean Range Baseline 161 154-165 119 107-124 161 154-165 119 107-124 Treatment first day 145 137-150 110 105-119 133 119-144 100 92-105 Treatment last day 143 132-152 103 101-106 140 117-151 101 91-106 Withdrawal day 1 167 154-186 117 111-130 155 121-170 109 95-118 Withdrawal day 2 171 155-190 120 112-137 169 145-191 119 109-134 Withdrawal day 3 170 156-194 117 112-129 173 151-189 125 117-141 Table 2 Plasma noradrenaline (nmol) before, during and after therapy with tiamenidine or clonidine Tiamenidine Clonidine Position Supine Upright Supine Upright Mean Range Mean Range Mean Range Mean Range Baseline 2.60 1.86-3.75 4.29 3.17-5.31 2.60 1.86-3.75 4.29 3.17-5.31 Treatment last day 1.85 1.60-2.01 2.56 2.20-2.88 1.45 1.09-1.87