Ephedrine actions

Ephedrine, which is not a catecholamine, has weak oral activity as a bronchodilator and although it has some direct action at adrenergic receptors, its predominant mode of action is by displacing norepinephrine from storage vesicules. 2"Agonists which are in use or are under investigation are the result of quests for improved selectivity, retention of potency, oral activity, and longer duration of action. 

Because of the widespread nature of adrenoceptors, nonselective P-agonists can produce many undesirable side effects. Therefore, before adrenergic agonists could become widely used in the treatment of asthma, some selectivity in action was needed. Whereas epinephrine and ephedrine have significant agonist activity at both a and P adrenoceptors, isoproterenol is a selective agonist at the P receptor (39). However, isoproterenol does not distinguish between the P and receptors and it is not active orally. 

These results indicate that in these new ester mydriatics, the structural factors, which influence the development of this type of pharmacological action are similar to those made evident by the chemical investigations of Jowett and Pyman and the pharmacological work of Marshall, Dale, Laidlaw and Cushny on the tropeines. The nature of the basic component is obviously important since mydriasis is produced by simple bases such as ephedrine. As regards the nature of the esterifying acid, Jowett and Pyman drew the following conclusions — ... 

According to Camus, hordenine is of low toxicity, but in large doses it causes death by arrest of respiration. It is less active than adrenaline but analogous in its action, resembling ephedrine rather than adrenaline. Barger and Dale found that the methiodide had a marked nicotine-... 

Ephedrine also oeeurs in the leaves of the yew tree [Taxus baccata) and in Sida rhombifolia Linn, whilst Stockman s cathine from Catha edulis Forsk has been shown by Wolfes to be d-nor- -ephedrine. Ghosh, Chopra and Dutt state that the bark of Moringa pterygosperma Gaertn. contains two alkaloids similar to ephedrine in pharmacological action. The more active of the two, moringinine, is amorphous the other is a liquid but jdelds a crystalline hydrochloride, C,H. HCl, m.p. 254-4°, + 1-8°, a picrate, m.p. 195°, and an aurichloride, m.p. 170-8°. 

In a monograph on ephedrine Gaddum has reviewed the differences in the action of adrenaline and ephedrine and has suggested that the latter has the same relation to adrenaline as physostigmine has to acetylcholine, that is, ephedrine inhibits the action of an enzyme system, which normally destroys adrenaline, or the substance closely resembling it, produced by adrenergic nerves. 

Omission of the side chain hydroxyl group from molecules based on epinephrine or ephedrine does not abolish the sympathomimetic activity of the resulting compounds. Many of these agents exert a considerable stimulant action on the central nervous system. As such, drugs in this class have been widely used—and... 

Primatene Dual Action Tablets—theophylline, ephedrine, guaifenesin... 

Chen KK, Poth EJ. Racial differences as illustrated by the mydriatic action of cocaine, euphthalmine and ephedrine. J Pharmacol Exp Ther 1929 36 429-445. 

BINAP Ru catalyst and (lR,25 )-ephedrine (Scheme 8-53). This result is similar to that obtained when catalyzed by pure (R)-BINAP. In pure (R)-BINAP complex-catalyzed hydrogenation, (S )-2-cyclohexenol can also be obtained with over 95% ee. This means that in the presence of (R)-BINAP-Ru catalyst, (R)-cyclohexenol is hydrogenated much faster than its (S )-enantiomer. When ephedrine is present, (R)-BINAP-Ru will be selectively deactivated, and the action of (S -BINAP-Ru leads to the selective hydrogenation of (S)-2-cyclohexenol, leaving the intact (R)-2-cyclohexenol in high ee. 

Muscarine-like action causing bronchospasm atropine and ephedrine are antagonists. Other parasympathetic effects include constriction of the pupil and of the ciliary muscles of the eye both effects are antagonized by atropine. 

Commercial samples containing approximately 400 mg of ephedra per capsule yield roughly 5 mg of ephedrine, 1 mg of pseudoephedrine, and less than 1 mg of methylephedrine (White et al. 1997). For a dose of four capsules, yielding approximately 20 mg of ephedrine, the elimination half-life is 5.2 hours. The time to reach maxium concentration is 3.9 hours. Compared to pure ephedrine tablets, the elimination kinetics of ephedra are comparable. However, ephedra showed somewhat different absorption kinetics (e.g., lag time, area under the concentration-time curve, and maximum plasma concentration). So, ephedra tablets may vary from pure ephedrine in the onset of action, but the durations of action are grossly equivalent. 

Routes used for trafficking in and attempted diversions of ephedrine and pseudoephedrine, identified through successful action by competent national authorities, 2003-2004... 

Finally, a few drugs have dual action— both direct and indirect. Dopamine, ephedrine, phenylpropanolamine, metaraminol, and amphetamines all belong to this group. 

Ephedrine is an alkaloid that is present in various forms of the ephedrine family, and which is still extracted from Ephedra sinica and Ephedra equisetina. Because of the presence of two asymmetric atoms, there are four isomeric forms. Pseudoepinephrine (d-isoephrine) is a stereoisomer with pharmacological action that differs slightly from ephedrine. The pharmacological action of ephedrine is typical of noncatecholamine sympathomimetics of mixed action. It stimulates both a- and 8-adrenoreceptors, and simultaneously causes a release of norepinephrine from synaptic neurons. Its vasoconstrictive ability is approximately 100 times weaker than that of epinephrine however, the duration of action is approximately 10 times longer. It is much less toxic than epinephrine, which allows it to be used widely in medicine. 

The pharmacological action of phenylpropanolamine is similar to the action of ephedrine. This sympathomimetic can temporarily elevate blood pressure, and it is used for the same indications as is ephedrine, which is primarily in combination with other drugs for catarrhal illnesses. In addition, it possesses weak central-stimulatory and anorectic action. The primary synonym is norephedrine. 

As drugs of mixed action, amphetamines activate adrenergic receptors and simultaneously release endogenic catecholamines (norepinephrine and dopamine) from neurons of the brain and periphery. Sympathomimetic effects on the periphery are very similar to those of ephedrine. Amphetamine elevates systolic and diastolic blood pressure and has weakly expressed, broncholytic action. These effects are more prolonged, yet less expressed, than with epinephrine. The distinctive feature of amphetamines is their psychostimulatory activity. Larger doses can cause hallucinations and mental conditions similar to paranoid schizophrenia. As a sympathomimetic, amphetamine is sometimes used for uterine inertia. Synonyms of amphetamine are phenamine and benzedrine. 

Amphetamine and cocaine also increase noradrenaline release and a number of drugs with mainly noradrenergic actions can also cause a hyperactive delirium. These include ephedrine, phenylpropanolamine, aminophylline, maprotiline and monoamine oxidase inhibitors (Hollister, 1986). 

Ephedrine is a naturally occurring alkaloid that can cross the blood-brain barrier and thus exert a strong CNS-stim-ulating effect in addition to its peripheral actions. The latter effects are primarily due to its indirect actions and depend largely on the release of norepinephrine. However, ephedrine may cause some direct receptor stimulation, particularly in its bronchodilating effects. Because it resists metabolism by both COMT and MAO, its duration of action is longer than that of norepinephrine. As is the case with aU indirectly acting adrenomimetic amines,... 

Amphetamine is an indirectly acting adrenomimetic amine that depends for its action on the release of norepinephrine from noradrenergic nerves. Its pharmacological effects are similar to those of ephedrine however, its CNS stimulant activity is somewhat greater. Both systolic and diastolic blood pressures are increased by oral dosing with amphetamine. The heart rate is frequently slowed reflexively. Cardiac output may remain unchanged in the low- and moderate-dose range. 

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