Pharmacological effects
1. The role of ephedrine
a. The role of the central nervous system: ephedrine has a clear central stimulatory effect, a larger therapeutic amount that can excited the cerebral cortex and subcortical center, causing insomnia, nervousness, anxiety, tremors and other symptoms. Breathing center and vasomotor center are also excited. Can shorten the hypnotic time of barbiturates. 5. The ephedrine's central nervous excitability is much stronger than adrenaline. Ephedrine excitates alpha1-adrenergic receptors in the periphery and also evokes central stimulatory effects by agonizing the central α1-adrenoceptor. Subcutaneous injection of ephedrine 50 ~ 100mg/kg can significantly increase the spontaneous activity of mice. Prazosin and α-methyl-p-tyrosine antagonized this effect of ephedrine, while sulpiride, propranolol, and reserpine did not diminish the enhanced effect of ephedrine on spontaneous activity in mice, suggesting that ephedrine Acts on α1-receptors but not on DA receptors. Ephedrine can increase the central pain threshold and produce analgesia.
b. Effects on the cardiovascular system: Ephedrine can increase myocardial contractility and increase cardiac output. In the overall situation, the vagus nerve is excited reflexively due to the increase of blood pressure, which offsets the effect of direct acceleration of the heart rate; if the vagus nerve reflex is blocked, the heart rate will be accelerated. Ephedrine has a strong stimulant effect on the heart, but repeated application, or a large dose at one time, is easy to produce inhibition; it may also disturb heart rhythm, but it is much weaker than adrenaline; in patients with severe organic heart disease, ephedrine and When digitalis is used together, it is easy to cause heart rhythm disorders. Ephedrine intravenous injection of epidural block slowed heart rate, stroke volume, cardiac output, heart index decreased significantly have a confrontation.
Ephedrine often causes systolic and diastolic pressures to rise, and pulse pressure increases. Give dogs a small dose (0.01 ~ 0.2mg/kg) intravenously, the blood pressure can be maintained for 10 to 15 minutes. Large dose (6 ~ 10mg/kg) intravenous injection, due to inhibition of heart and blood pressure. Ephedrine intravenous 0.1 ~ 3.0mg/kg, cat pulmonary artery pressure, systolic blood pressure, diastolic blood pressure and vascular resistance were significantly increased, and the effective amount of dependence. The ephedrine has a mild and long-lasting vasoconstriction, and its vasodilation effect is very weak. Therefore, it is used for swelling of the nasal mucosa with long contraction and no secondary vasodilation; it can expand coronary blood vessels, increase coronary flow, and the pituitary When vasopressin is used for boosting, it can overcome the coronary vasoconstriction and cardiac inhibition caused by a large number of pituitrin. The boosting effect of ephedrine is slow and lasting for several hours. The increase of systolic blood pressure is more significant than that of diastolic blood pressure, and the diastolic pressure does not generally decrease.
The effect of ephedrine on blood vessels is a combination of direct and indirect effects. The chemical structure of ephedrine is similar to that of adrenaline, and it can directly bind to adrenergic α and β receptors to produce adrenergic effects. It also acts on adrenergic nerve endings to promote the release of norepinephrine. Animal experiments show that the effect of ephedrine can be weakened by cocaine, and it can also be blocked by phentolamine.
c. Effect on smooth muscle: Ephedrine has a significant relaxing effect on bronchial smooth muscle. Especially in the bronchial spasm is more significant. Experiments show that ephedrine is effective against acetylcholine and histamine-induced spasms. Its strength is not as strong as epinephrine, but its effect is more permanent and effective oral administration. It is often used in asthma. Ephedrine can relax gastrointestinal smooth muscle, inhibit motility, and delay the advancement and emptying of gastrointestinal contents. Ephedrine generally exhibits increased tension and amplitude in the uterus of the animal. This excitatory effect can be blocked by ergotamine and enhanced by cocaine. However, the uterus in humans is generally inhibited and used to relieve menstrual pain. Ephedrine can increase the tension in the deltoid and sphincter muscles. Ephedrine reduces the number of micturitions, enough to produce urinary retention, and is effective for children with enuresis. Ephedrine can also eliminate symptoms of nocturnal enuresis or incontinence of the bladder sphincter. Ephedrine can cause and enhance the spontaneous contraction of the mouse vas deferens, and phentolamine can significantly counteract the effects of ephedrine, whereas reserpine has no significant effect on this.
d. Others: Ephedrine has anti-fatigue effect on skeletal muscles and can promote conduction between nerves and muscles inhibited by arrow poisons. It can be used for the treatment of myasthenia gravis; it can also cause hyperglycemia, but its effect is weak but not constant. . Both ephedrine and Ephedra alkaloids do not exhibit sweating effects on normal and febrile cats. In general, ephedrine does not induce sweat in humans, but when the person is in a high-temperature environment, ephedrine is used at 50-60 mg. After 2 hours, sweat secretion is much faster than those without ephedrine, but the topical skin of ephedrine subcutaneously does not cause specific sweat secretion. Therefore, this effect of ephedrine may be central. And ephedrine has the effect of increasing the metabolic rate. After injecting 50 mg of ephedrine sulfate into six normal adults, the metabolic rate increased by 14.2% compared with that before injection. The ephedra water extract and ethanol extract acted on lung sections of sensitized guinea pigs to inhibit the amount of free allergens.
The effects of ephedrine are mixed, mostly due to the direct effect of binding to adrenergic receptors, and a small part due to the indirect factors that promote mediator release. When ephedrine is repeatedly applied, it is easy to produce rapid tolerance, and the effect is rapidly weakened. Finally, it can be completely ineffective. It can be recovered after several hours. There are also two direct and indirect factors in the mechanism of rapid tolerance. Some people use isolated rabbits. Aortic strips were tested and it was suggested that ephedrine may have other receptors for aortic smooth muscle in addition to its effects on adrenergic receptors; it was also suggested that the rapid tolerance of methamphetamine is related to central regulation, but destruction No effect was found after the lateral reticular nucleus.
2. The role of pseudoephedrine
a. Diuretic effect: pseudoephedrine has a significant diuretic effect compared to ephedrine. After using water, saline and urea, the urine output will be further increased, but the urine output will be reduced for anesthetized dogs. The dogs with mild experimental glomerulonephritis remain Produce diuretic reactions, severe cases no diuretic effect. After an intravenous injection, the effect lasts 30 to 60 minutes. The principle of diuresis is thought to be due to an increase in renal blood flow caused by renal vasodilation. Due to diuresis, the kidney volume also increases.
b. Effects on Smooth Muscle: The extremely dilute solution of pseudoephedrine, like ephedrine, stimulates sympathetic nerves and causes bronchiectasis; concentrated solutions can relax the muscles of the trachea due to paralysis of the muscles; moderate concentrations cause bronchoconstriction.
c. Others: Pseudoephedrine has a slight excitatory vascular effect; ephedrine is the strongest in the role of pressure increase, contraction of nasal mucosa and blood vessels, followed by synthetic ephedrine (Ephetonin) and pseudoephedrine the weakest. The toxicity was also the strongest (100%) of ephedrine, followed by racemic ephedrine (78%) and pseudoephedrine (56.5%).
3. The effect of ephedra is that ephedrine can lower blood pressure, increase the contraction of isolated guinea pig uterus and peristalsis of isolated rabbit intestine, and ephedra root extract intravenous injection in cats and rabbits also has antihypertensive effect.
4. The effect of Ephedra volatile oil Ephedra volatile oil has a sweating effect. Its inhibitory effect on the central nervous system can be antagonized by the central stimulant effect of ephedrine. Ephedra volatile oil has different degrees of inhibition on Haemophilus influenzae, Streptococcus A, Streptococcus pneumoniae, Neisseria, Bacillus subtilis, Escherichia coli, and Candida albicans. In vitro tests have shown that it has a strong inhibitory effect on influenza virus, and it has a therapeutic effect on subcutaneous injection of A-type and PR8-type influenza viruses in mice. 2. Ephedra volatile oil emulsion has an antipyretic effect on rabbits that have been artificially heated by intramuscular injection of bovine milk. Ephedra volatile oil and its main component terpineol have a cooling effect on the body temperature of normal mice, but Ephedrae volatile oil is not as effective as terpineol. Ephedra volatile oil emulsion intragastric administration, intramuscular injection, intraperitoneal injection showed no sweating effect on normal and febrile cats, and no sweating effect on fever patients. Maxing Shigan Decoction had antiviral effect on the 61-1 strain of influenza virus in Shaanxi in the experiment of chicken embryos, which was mainly the function of ephedra. The antiviral effect of gypsum, licorice and almond on ephedra was not synergistic. Ephedra and licorice in Maxing Shigan Decoction have a certain inhibitory effect on Staphylococcus aureus and Pseudomonas aeruginosa. The effect of ephedra is strong.
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