SAR of Sympathomimetic Agents: Indirect Acting Agents: Hydroxyamphetamine, Pseudoephedrine, Propylhexedrine : Pharmaguideline -->

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SAR of Sympathomimetic Agents: Indirect Acting Agents: Hydroxyamphetamine, Pseudoephedrine, Propylhexedrine

Indirect sympathomimetics work by causing endogenous NE to be released. Active absorption enables them to displace NE from the storage granules.
Indirect sympathomimetics work by causing endogenous NE to be released. Active absorption enables them to displace NE from the storage granules in the nerve ending.


Mechanism of the action - Norepinephrine is released from the central adrenergic receptors when it is administered. When hydroxyl - amphetamines act on adrenergic nerve terminals, alpha and B receptors in the peripheral nervous system, noradrenaline is released.

Metabolism - Amphetamine is converted from the cytochrome P450 to 4-hydroxyamphetamine by CYP2D6, a liver enzyme. 4-Hydroxyamphetamine is metabolised by dopamine beta-hydroxylase into 4-hydroxynorephedrine and excreted in the urine.

Therapeutic uses -
It is used to dilate the pupil during diagnostic eye tests and eye surgery. It is used to treat the narcolepsy, depressive disorders, motion sickness, and obesity as well .

Adverse reactions - It can cause dry mouth, agitation, sleeplessness, and anorexia. Hypertension, tachycardia, angina discomfort, and also cardiac arrhythmia may occur with larger doses.


i. 4-methoxybenzaldehyde and nitroethane react together in the presence of the main amine to provide benzene 1-methoxy-4 - ((Z) -2-nitroprop-1-enyl).
ii. The final combination of iron and HCl provides 1- (4-methoxyphenyl) propan-2-one.
iii. In response to amide, an unstable compound produces HCl treatment that produces 1- (4-methoxyphenyl) propan-2-amine.
iv. At a reaction of 40% HBr, hydroxyamphetamine is certainly produced.


It is ephedrine's (S, S) diastereoisomer.

Mechanism of the action - Ephedrine has a mixed method of action, whereas L-(+) pseudoephedrine operates mostly through an indirect mechanism with little direct activity.

Metabolism - Incompletely metabolized to inactive molecules in the liver by N-demethylation. Excretion: Between 55% and 75% of the dosage is excreted unaltered in urine, with the remaining being eliminated as unmodified medication and metabolites.

Therapeutic uses - Because of its lack of direct action, L-(+) pseudoephedrine has less CNS effects than ephedrine. This ingredient can be found in a variety of over-the-counter nasal decongestants and cold treatments.

Adverse reactions - A typical adverse drug response (ADRS) linked with the pseudoephedrine treatment is central nervous system stimulation, insomnia, uneasiness, excitability, dizziness, and anxiety. Tachycardia and palpitations are its’ uncommon adverse reactions. Pseudoephedrine medications are infrequently associated with the mydriasis (dilated pupils), stroke, heart arrhythmias, hypertension, seizures, seizures, ischemic colitis, and severe skin reactions such as pseudo-scarlatina and systemic contact dermatitis.

Pseudoephedrine is a phenethylamine and ephedrine diastereomer with sympathomimetic properties. Pseudoephedrine releases norepinephrine into the final vesicles in presynaptic neurones, thereby releasing norepinephrine to neuronal synapses where it primarily activates alpha-adrenergic receptors. It also has a weak agonist activity directly on the alpha- and beta-adrenergic receptors. Receptor stimulation causes vasoconstriction and reduces nasal congestion and sinus congestion.


It is another amphetamine analogue in which the aromatic ring has been substituted with a cyclohexane ring.

Mechanism of the action - This medication causes vasoconstriction as well as a decongestant action on the nasal membranes. The central nervous system is affected less by this drug.

Metabolism - Propylhexedrine is broken down into vanous metabolites such as norpropylhexedrine, cyclohexylacetoxime, and cis and trans-4-hydroxypropylhexedrine.

Therapeutic uses - Its major usage is as a local vasoconstrictor on the nasal mucosa to relieve symptoms of nasal congestion caused by a common cold, allergic rhinitis, or sinusitis.

Adverse reactions - Nasal discharge increases as a result of burning, stinging and sneezing.

Propylhexedrine is based on propylamine with sympathomimetic properties. Propylhexedrine binds and activates alpha-adrenergic receptors in the mucosa of the respiratory tract, thereby mimicking the actions of norepinephrine and epinephrine. This causes vasoconstriction and reduces inflammation and inflammation of the mucous membranes, thus relieving nasal congestion and sinus.
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