INTRODUCTION-
Phenylephrine is a sympathomimetic amine that acts predominantly on a-adrenergic receptors. It is mainly used to treat nasal congestion, but may also be useful in treating hypotension and shock, hypotension during spinal anaesthesia, prolongation of spinal anaesthesia, paroxysmal supraventricular tachycardia, symptomatic relief of external or internal hemorrhoids, and to increase blood pressure as an aid in the diagnosis of heart murmurs.
MECHANISM OF ACTION-
In general, a1-adrenergic receptors mediate contraction and hypertrophic growth of smooth muscle cells. a1-receptors are 7-transmembrane domain receptors coupled to G proteins, Gq/11. Three a1-receptor subtypes, which share approximately 75% homology in their transmembrane domains, have been identified: a1A (chromosome 8), a1B (chromosome 5), and a1D (chromosome 20). Phenylephrine appears to act similarly on all three receptor subtypes. All three receptor subtypes appear to be involved in maintaining vascular tone. The a1A-receptor maintains basal vascular tone while the a1B-receptor mediates the vasocontrictory effects of exogenous a1-agonists. Activation of the a1-receptor activates Gq-proteins, which results in intracellular stimulation of phospholipases C, A2, and D. This results in mobilization of Ca2+ from intracellular stores, activation of mitogen-activated kinase and PI3 kinase pathways and subsequent vasoconstriction. Phenylephrine produces its local and systemic actions by acting on a1-adrenergic receptors peripheral vascular smooth muscle. Stimulation of the a1-adrenergic receptors results in contraction arteriolar smooth muscle in the periphery. Phenylephrine decreases nasal congestion by acting on a1-adrenergic receptors in the arterioles of the nasal mucosa to produce constriction; this leads to decreased edema and increased drainage of the sinus cavities
USES-
used for the temporary relief of stuffy nose, sinus, and ear symptoms caused by the common cold, flu, allergies, or other breathing illnesses (e.g., sinusitis, bronchitis).
SIDE EFFECT-
1-Mild upset stomach
2- trouble sleeping
3- dizziness
4- lightheadedness
5- headache
6- nervousness
7- shaking or fast heartbeat may occur.
DRUG DRUG INTERACTION-
1-Acebutolol
The risk or severity of adverse effects can be increased when Acebutolol is combined with Phenylephrine.
2-Acetaminophen
The serum concentration of Phenylephrine can be increased when it is combined with Acetaminophen.
3-Acetylsalicylic acid
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Acetylsalicylic acid.
4-Alfuzosin
Alfuzosin may decrease the vasoconstricting activities of Phenylephrine.
5-Aminophylline
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Aminophylline.
6-Amitriptyline
Amitriptyline may increase the activities of Phenylephrine.
7-Amphetamine
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Amphetamine.
8-Arformoterol
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Arformoterol.
9-Armodafinil
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Armodafinil.
10-Articaine
The risk or severity of adverse effects can be increased when Phenylephrine is combined with Articaine.
REFERENCE-
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