Cardiovascular regulation during administration of co-dergocrine to normal subjects

Dopamine and sympathoadrenal activity in man

The sympathetic adrenal (SA) activity can be modulated by dopamine (DA) through D2 receptors. In man, using D2 antagonists, it has been demonstrated that endogenous DA plays an inhibitory modulation of the SA system during high degree of SA activation. D2 agonists are able to induce a decrease in norepinephrine (NE) release either in vitro or in vivo. This effect leads, in vivo, to a decrease in blood pressure (BP) and to an activation of arterial baroreceptors. Therefore, in vivo, the D2 mediated inhibition of epinephrine (E) release, which is clearly demonstrated in vitro, is overwhelmed by the baroreceptor-mediated activation of the splachnic nerve. As a consequence, the in vivo administration of D2 agonists can induce a different effect on the net peripheral sympathetic tone of an organ, depending on the balance between the degree of the baroreceptor-mediated sympathetic activation and the inhibitory D2-mediated inhibition of NE release at the tissue level. In the present paper we investigated the in vivo effect of placebo (PL) or acute oral bromocriptine (BC) administration on plasma CA and on the cardiac sympatho-vagal balance of 7 normal volunteers, as assessed by power spectral analysis of heart rate (HR) variability (autoregressive method), either in resting or sitting position. Low frequency (LF) and high frequency (HF) components, both expressed in normalized units (nU), and LF/HF ratio were calculated. BC caused a decrease in BP, plasma NE and no change in HR in resting and sitting position. Plasma E increased in sitting position. At the heart level, after BC, we observed, during rest, an increase in LF and LF/HF ratio and a decrease in HF while in sitting position LF did not increase further. These data show that BC, while reducing BP through a decrease of plasma NE, increases LF/HF ratio (sympathetic tone) without any change in heart rate. These data seem to confirm that BC causes an inhibitory modulation of the SA system acting predominantly at the periphery through D2 presynaptic receptors.

Clinical pharmacokinetics of the nifedipine/co-dergocrine combination in impaired liver and renal function

Following a single oral dose of 20 mg nifedipine combined with 2 mg co-dergocrine to 24 subjects, the pharmacokinetics of this drug were studied. 8 normotensive subjects had normal renal and hepatic function, 8 patients had chronic renal insufficiency (creatinine clearance less than 30 ml.min-1) and 8 patients had liver cirrhosis which was confirmed by liver biopsy. The area under the plasma level time curve (AUC infinity) of co-dergocrine increased from 0.59 +/- 0.41 ng.ml-1. (mean +/- SD) in the normals to 1.24 +/- 0.95 ng.ml-1.h in liver cirrhosis (P less than 0.05) and to 1.81 +/- 0.9 ng.ml-1.h in renal failure (P less than 0.05 compared with the control group). Corresponding values for the nifedipine AUC infinity were 564.5 +/- 268 ng.ml-1.h, 1547.5 +/- 1134 (P less than 0.05) and 929 +/- 533 ng.ml-1.h (P less than 0.05; gas chromatographic method). The incidence of adverse effects was lower in patients with renal failure than in subjects with normal renal and liver function as well as in those with liver cirrhosis.

Cardiovascular regulation and lipoprotein profile during administration of co-dergocrine in essential hypertension

Co-dergocrine has recently been demonstrated acutely to lower plasma norepinephrine (NE) and blood pressure (BP) in patients with essential hypertension, and similar results have been obtained during chronic administration of co-dergocrine to healthy men. The present study investigated the effect of 3 weeks of treatment with co-dergocrine 4 mg/day on BP, plasma catecholamines, certain other BP-regulating factors and serum lipoproteins in patients with essential hypertension. Compared to placebo conditions, co-dergocrine decreased supine BP and heart rate by -7% and the upright plasma NE level by -24%. Supine plasma NE also fell (-24%). Total cholesterol and the LDL + VLDL-cholesterol lipoprotein fraction were lowered by -6%. No significant change was observed in plasma renin activity, angiotensin II, aldosterone and epinephrine levels, whole blood and plasma volume, exchangeable sodium, and the cardiovascular responsiveness to NE, angiotensin II and isoproterenol. The findings suggest that in patients with essential hypertension, chronic treatment with co-dergocrine may slightly decrease sympathetic outflow and, at least in the short-term, lower the potentially atherogenic serum LDL + VLDL - cholesterol fraction.

Inhibition of the aldosterone response to sodium depletion in man by stimulation of dopamine DA2 receptors

In this study we have investigated the effect of co-dergocrine, a selective DA2-agonist, on plasma aldosterone concentrations (PAC) in twelve patients with essential hypertension both in basal conditions and during sodium depletion. Sodium depletion resulted in an increase of PAC from 38 (13) pg/ml to 297 (21) pg/ml. The PAC response to sodium depletion was reduced to 155 (29) pg/ml by co-dergocrine. No significant PAC changes were found in patients maintained on a normal sodium intake. In addition the drug did not significantly modify plasma renin activity (PRA) in either experimental group. These results suggest that the dopaminergic inhibition of aldosterone secretion in man is mediated by DA2 receptors in the adrenal cortex.

The absolute systemic availability of a new oral formulation of co-dergocrine in healthy subjects

We have studied the absolute systemic availability (f) of an oral formulation (Hydergin spezial = Hydergine FASR 4 mg per tablet) of co-dergocrine by three different methods. Twelve healthy volunteers received single doses of 0.9 mg co-dergocrine intravenously and 8.0 mg orally in a randomized crossover design. The pharmacological effect of co-dergocrine was monitored as a reduction in plasma prolactin. Maximal plasma concentrations of co-dergocrine after oral dosing ranged between 0.181 and 1.307 ng.ml-1. Maximal urinary excretion ranged between 4.7 and 9.9 micrograms.h-1 and between 0.3 and 2.3 micrograms.h-1 after intravenous and oral doses respectively. Clearance was measured as 90 +/- 22 l.h-1 and the absolute systemic availability (f) as 2.25 +/- 0.65% by using the areas under the plasma concentration-time curves extrapolated to infinity. Calculation of f by comparing areas up to 32 h or the fractions of the dose excreted in urine led to identical results. The intravenous and oral doses produced similar pharmacological effects (reduction of plasma prolactin concentrations) despite the small value of f.

Is stimulation of prejunctional dopamine receptors an antihypertensive principle?

Bromocriptine and co-dergocrine (Hydergine R) reduce blood pressure and heart rate in experimental animals largely by stimulating DA2 receptors. A stimulant effect on DA1 receptors can be demonstrated in isolated tissues, but this action does not appear to make an important contribution to the depressor response to the two compounds, since effects are abolished by DA2 receptor blockade. Although both compounds are known to penetrate the brain, their antihypertensive effects, and the concomitant reductions in plasma noradrenaline levels produced in hypertensive patients can be prevented by domperidone, confirming a peripheral site of action. A review of the data available concerning the cardiovascular effects of bromocriptine and co-dergocrine in animals and man suggests that a DA2 receptor stimulant is effective in the treatment of hypertension.