Phenylephrine Pharmacology


About Phenylephrine
An a1-adrenergic receptor agonist, Phenethylamine derivative, Decongestant, Antiglaucoma, Mydriatic.
Mechanism of Action of Phenylephrine
The drug exerts it`s pharmacological action by acting as a selective alpha-1 adrenergic agonist. It causes vasoconstriction and increases total peripheral resistance and raises blood pressure. It reduces intraocular tension by constricting ciliary body blood vessels and produce mydriasis (without cycloplegia). It exerts nasal decongestant action; by vasoconstrictory action on arterioles of nasal mucosa. It prolongs and localizes the action of anaesthetics due to it`s vasoconstrictory action on skin, mucous membrane, and viscera and thus slows the rate of absorption of local anaesthetics.
Pharmacokinets of Phenylephrine
Absorption: Variable depending up on the route of administration. Metabolism: Metabolized in the liver and intestine.
Onset of Action for Phenylephrine
Nasal: Rapid
Ophthalmic: Rapid
I.V.: Rapid
I.M.: Within 15 minutes
Duration of Action for Phenylephrine
Nasal: ? to 4 hours
Ophthalmic: 3 to 7 hours
I.V.: 15 to 20 minutes
I.M.: ? to 2 hours.

Half Life of Phenylephrine
Side Effects of Phenylephrine
6.Premature ventricular contractions
11.Brow ache(with ophthalmic form)
12.Burning or stinging in eye
13.Blurred vision
14.Elevated intraocular pressure
16.Episodes of asthma

Contra-indications of Phenylephrine
1.Hypersensitivity to the drug
3.Ventricular tachycardia and severe hypertension (Injected form)
4.Angle closure glaucoma and in those who wear soft contact lenses(ophthalmic form)
Special Precautions while taking Phenylephrine
1.Coronary diseases
2.Advanced arteriosclerosis
4.Partial heart block
5.Myocardial diseases
8.Nasal and ophthalmic form use cautiously in type-1 diabetes mellitus

Pregnancy Related Information
Use with caution
Old Age Related Information
Use with caution
Breast Feeding Related Information
Use with caution
Children Related Information
Use with caution
Below age 6:contraindicated
Indications for Phenylephrine
2.Paroxysmal supra ventricular tachycardia
3.Maintain blood pressure during spinal and inhalation anaesthesia
4.Prolongation of spinal anaesthesia
6.Mydriasis(without cycloplegia)
7.Nasal congestion.

Interactions for Phenylephrine
May interact with systemically administered MAOIs.
Typical Dosage for Phenylephrine
I.M. or S.C.: 2 to 5mg. Then if required; give doses up to 10mg.
Slow I.V. injection: 0.1 to 0.5mg. Then if required; repeat after 15 minutes.
I.V. infusion: Starts with 0.18mg/minute. Then adjust the dosage up to 0.03 to 0.06mg/minute based on patient`s response.
Nasal congestion: Apply 2 to 3 drops or 1 to 2 sprays of 0.25% to 1% solution instilled in each nostril.
Mydriasis (without cycloplegia): Instill 1 to 2drops 2.5% or 10% solution in eye. Repeated if required.
Prolongation of spinal anaesthesia: 2 to 5mg added to anaesthetic solution.
Schedule of Phenylephrine
Storage Requirements for Phenylephrine
Store at controlled room temperature at range of 15 to 30 degree C. in a well closed container. Protect from light.
Effects of Missed Dosage of Phenylephrine
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Phenylephrine
Discontinue the drug and give supportive and symptomatic treatment. Closely monitor vital signs. Use atropine sulfate to block reflex Bradycardia. Treat excessive hypertension with phentolamine. Treat cardiac arrhythmia with propranolol. Treat excessive mydriatic effect with levodopa.

Home Delivery for Phenylephrine in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including phenylephrine.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for phenylephrine and other medicines and health products. Home delivery services for phenylephrine may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take phenylephrine only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for phenylephrine before they complete the sale. You can get this information while placing the order for phenylephrine with the pharmacy.

Phenylephrine is a generic medicine name and there are several brands available for it. Some of the brands for phenylephrine might be better known than phenylephrine itself. If the pharmacy that's willing to deliver medicines to your home doesn't have phenylephrine in stock, you can ask for one of the branded alternatives for phenylephrine.