Dosing of Medicine differ in Adult & Pediatrics ↓

Adult Dose

S.No	Ailment	Route	Dose Min	Dose Max	Unit	Dosage Form	Frequency	Additional Info
1	Nasal congestion	Topical	0.25	1	%	Nasal drops/Nasal sprays		Into each nostril every 4 hours as required. Or phenylephrine hydrochloride may be given in usual oral doses of 10 mg every four hours (up to a maximum of 60 mg daily) or 12 mg up to four times daily.
2	Mydriatic	Topical	2.5	10	%	Ophthalmic Solution		Above conc. are used but systemic absorption can occur and the 10% strength, in particular, should be used with caution. Solutions containing 2.5% or more may cause intense irritation and a local anaesthetic other than butacaine (which is incompatible) should be instilled into the eye a few minutes beforehand.
3	Conjunctival decongestant	Topical	0.12		%	Ophthalmic Solution
4	Hypotension	s.c/ i.m				Injection		For hypotension, an initial dose of phenylephrine hydrochloride 2 to 5 mg may be given as a 1% solution subcutaneously or intramuscularly with further doses of 1 to 10 mg if necessary, according to response. In severe hypotensive states, 10 mg in 500 mL of glucose 5% or sodium chloride 0.9% has been infused intravenously, initially at a rate of up to 180 micrograms/minute, reduced, according to the response, to 30 to 60 micrograms/minute.
5	Paroxysmal supraventricular tachycardia	IV		500	micrograms	Injection		To stop paroxysmal supraventricular tachycardia other drugs are preferred. The initial dose is usually not greater than 500 micrograms given as a 0.1% solution with subsequent doses gradually increased in increments of 100 to 200 micrograms up to 1 mg if necessary.

Adult Dose

S.No	Ailment	Route	Dose Min	Dose Max	Unit	Dosage Form	Frequency	Additional Info
1	Nasal congestion	Topical	0.25	1	%	Nasal drops/Nasal sprays		Into each nostril every 4 hours as required. Or phenylephrine hydrochloride may be given in usual oral doses of 10 mg every four hours (up to a maximum of 60 mg daily) or 12 mg up to four times daily.
2	Mydriatic	Topical	2.5	10	%	Ophthalmic Solution		Above conc. are used but systemic absorption can occur and the 10% strength, in particular, should be used with caution. Solutions containing 2.5% or more may cause intense irritation and a local anaesthetic other than butacaine (which is incompatible) should be instilled into the eye a few minutes beforehand.
3	Conjunctival decongestant	Topical	0.12		%	Ophthalmic Solution
4	Hypotension	s.c/ i.m				Injection		For hypotension, an initial dose of phenylephrine hydrochloride 2 to 5 mg may be given as a 1% solution subcutaneously or intramuscularly with further doses of 1 to 10 mg if necessary, according to response. In severe hypotensive states, 10 mg in 500 mL of glucose 5% or sodium chloride 0.9% has been infused intravenously, initially at a rate of up to 180 micrograms/minute, reduced, according to the response, to 30 to 60 micrograms/minute.
5	Paroxysmal supraventricular tachycardia	IV		500	micrograms	Injection		To stop paroxysmal supraventricular tachycardia other drugs are preferred. The initial dose is usually not greater than 500 micrograms given as a 0.1% solution with subsequent doses gradually increased in increments of 100 to 200 micrograms up to 1 mg if necessary.

Ref :-  Book : Martindale    Page : 1672, 1673   Edition : 38  

Pediatric Dose

Ref :- Book : Nelson's textbook of Pediatrics    Page : 313, 780   Edition : 19  

Precaution :- If a Patient is using 'Phenylephrine' drug in chronic pharyngitis disease, then Please its preparations in cough syrups is to be used with caution and best is to avoid it.   if he ever suffered from hypertension disease.
►  Side Effect : Headache, Insomnia, Nervousness, Rebound nasal cogestion, Serious adverse effects are, Cardiac arrhythmia, Hypertension
Ref :-   Book : Principle of Pharmacology (The Pathophysiologic Basis of Drug Therapy)    Page : 144   Edition : 3.  
►  Drug Interaction : Drug interaction of Phenylephrine is with (including RIMAs),  Aminophylline , Halothane , Acarbose , Phenelzine, Moclobemide
Ref :-   Book : Martindale    Page : 1673   Edition : 37.  

Drug interaction

Drug Interaction : Drug interaction of Phenylephrine is with (including RIMAs),  Aminophylline , Halothane , Acarbose , Phenelzine, Moclobemide

Book : Martindale    Page : 1673   Edition : 37.  

  ►    Mechanism of Drug Drug Interaction :  Phenylephrine has mainly direct alpha-agonist properties and is less liable than adrenaline or noradrenaline to induce ventricular fibrillation if used as a pressor agent during anaesthesia with inhalational anaesthetics such as cyclopropane and halothane; nevertheless, caution is necessary. MAOIs like Phenelzine inhibit the metabolism of some amine drugs (notably indirect-acting sympathomimetics like Phenylephrine), which can lead to dangerous enhancement of their pressor effects. Monoamine oxidase inhibitors (MAOIs) inhibit the action of monoamine oxidase, the enzyme responsible for the metabolism of several biogenic amines and; Reversible inhibitors of monoamine oxidase type A (RIMAs) include moclobemide; therefore medicines containing sympathomimetics (like phenylephrine), should not be taken with moclobemide.
Ref :-   Book : Martindale    Page : 438,442,1673   Edition : 37.  

Mechanism of Drug

Mechanism of Drug Drug Interaction : Phenylephrine has mainly direct alpha-agonist properties and is less liable than adrenaline or noradrenaline to induce ventricular fibrillation if used as a pressor agent during anaesthesia with inhalational anaesthetics such as cyclopropane and halothane; nevertheless, caution is necessary. MAOIs like Phenelzine inhibit the metabolism of some amine drugs (notably indirect-acting sympathomimetics like Phenylephrine), which can lead to dangerous enhancement of their pressor effects. Monoamine oxidase inhibitors (MAOIs) inhibit the action of monoamine oxidase, the enzyme responsible for the metabolism of several biogenic amines and; Reversible inhibitors of monoamine oxidase type A (RIMAs) include moclobemide; therefore medicines containing sympathomimetics (like phenylephrine), should not be taken with moclobemide.

Book : Martindale    Page : 438,442,1673   Edition : 37.  

►  Contraindication : Narrow-angle glaucoma, Severe hypertension or tachycardia (contraindication for IV form of phenylephrine)
Ref :-   Book : Principle of Pharmacology (The Pathophysiologic Basis of Drug Therapy)    Page : 144   Edition : 3.  

  ►  Mechanism of Action :   Selectively activate alpha1 adrenergic receptors to increase peripheral vascular resistance
Ref :-   Book : Principle of Pharmacology (The Pathophysiologic Basis of Drug Therapy)    Page : 144   Edition : 3.  

►   Route of Elimination :   Gut, Hepatic (Metabolism)
Ref :-   Book : Martindale    Page : 1672   Edition : 38.  
►    Plasma Half-life :   Min value :-   NA    Max value :-   NA

►    Peak Plasma Concentration :   Min value :-   NA    Max value :-   NA