The indirect sympathomimetic activity of etilefrine--a comparison with tyramine and ephedrine using [3H] noradrenaline

Ephedra intermedia Schrenk & C. A. Mey Methanol Extract: Nanoencapsulation by Mini-Emulsion Polymerization and its Release Trend under Simulated Conditions of the Human Body

In this research, the extract of Ephedra intermedia Schrenk & C.A.Mey. was encapsulated using the mini-emulsion polymerization method based on methyl methacrylate polymers with a nanometer size. The encapsulated extract was characterized using different analytical techniques. Furthermore, the loading efficiency and release of the plant extract were examined. FT-IR spectroscopy confirmed the formation of an expectational product. The TEM and SEM imaging showed a spherical morphology for the prepared encapsulated extract. The average size of poly-methyl-methacrylate nanoparticles containing Ephedra extract was found to be approximately 47 nm. The extract loading efficiency and encapsulation efficiency test demonstrated a dose-depending behavior on E. intermedia extract for both analyses, which is highly advantageous for traversing biological barriers. The release assay shows a controlled release for the extract at phosphate buffer solution (PBS). A 38 % release was calculated after 36 hours. The results obtained from the present study reveal that encapsulating the plant extract is a suitable alternative to control and increase their medicinal properties.

Reinforcing effect of pseudoephedrine isomers and the mechanism of action

It has been proposed that ephedrine and its isomers may have abuse potential. When made available to rhesus monkeys (n = 4) for self-administration, +-pseudoephedrine functioned as a positive reinforcer in all monkeys, as did (-)-pseudoephedrine in two of three monkeys. Pseudoephedrine isomers were 10- to 33-fold less potent than cocaine. In in vitro binding in monkey brain tissue, both isomers had low affinity for dopamine and serotonin transporters by at least 200-fold relative to cocaine, but comparable affinity for norepinephrine transporters. +-Pseudoephedrine also blocked dopamine uptake in 293 hDAT cells with low potency relative to cocaine. When given in vivo +-pseudoephedrine significantly displaced radioligand binding to dopamine transporters with a potency comparable to that in self-administration. Therefore, pseudoephedrine isomers can function as reinforcers and the mechanism at dopamine transporters may underlie this effect. However, pseudoephedrine appears to be a weak reinforcer and may have relatively low abuse potential.

Pharmacological analysis of positive chronotropic and inotropic responses to etilefrine in isolated dog heart preparations

Positive chronotropic and inotropic responses to etilefrine (alpha-[(ethylamino)methyl]-m-hydroxybenzyl alcohol), an orally active cardiovascular agent, were investigated in isolated dog right atrial and left ventricular preparations. Intravenous administration of etilefrine to a support dog increased heart rate and mean systemic blood pressure, and increased sinus rate and atrial contractile force in the isolated right atrium perfused with blood from the support dog. Etilefrine injected intra-arterially to isolated atria and ventricles induced dose-dependent positive chronotropic and inotropic effects. Etilefrine was about 100 times less potent than isoproterenol. The effects of etilefrine in isolated atria were significantly inhibited by treatment with atenolol, but were not significantly inhibited by ICI 118,551. The effects of etilefrine were partially inhibited by imipramine. These results indicate that etilefrine is a highly selective beta-1 adrenoceptor agonist and suggest a moderate catecholamine-releasing activity by tyramine-like action in the blood-perfused dog heart.

The effects of ephedrine and etilefrine on uterine and fetal blood flow and on fetal myocardial function during spinal anaesthesia for caesarean section

The effects of two vasopressors, ephedrine and etilefrine, on blood flow in maternal uterine, fetal umbilical, middle cerebral and renal arteries and on fetal myocardial function were studied by colour Doppler and M-mode echocardiography techniques during spinal anaesthesia for caesarean section. There were 7 healthy pregnant women in each treatment group. The vascular resistance of maternal uterine arteries increased significantly after both of the vasopressors while the vascular resistance of the umbilical artery remained unchanged. Ephedrine decreased the blood velocity waveform indices in the fetal middle cerebral and renal arteries, increased fetal right ventricular contractility and decreased left ventricular inner end-diastolic dimension. Fetal heart rate was unchanged. Etilefrine caused no detectable changes in fetal haemodynamics or in fetal myocardial function. These findings demonstrate that vasopressors administered for the treatment of minor maternal arterial pressure fall produce vasoconstriction in the uterine circulation during spinal anaesthesia, yet healthy fetuses seem to tolerate these haemodynamic alterations well. On the other hand, ephedrine caused changes in fetal myocardial function and in the vascular resistance of fetal middle cerebral and renal arteries, which demonstrates the potential modifying effect of vasoactive drug given to the mother on fetal haemodynamics.

The effect of sympathomimetic agents on noradrenaline efflux from a blood vessel

The effect of several sympathomimetic agents on the efflux of noradrenaline and its metabolites has been evaluated using the ventral artery of the rat tail as the experimental model. This vessel is richly endowed with sympathetic nerves and is therefore well suited to examine the efflux patterns of that transmitter. Etilefrine, tyramine, ephedrine and REN-293 were all found to increase the efflux of 3H-noradrenaline and/or 3H-DOPEG to different degrees from the artery. Possible reasons for this variation in metabolite efflux are discussed.