Actions of Phenylephrine Hydrochloride in details
Phenylephrine Hydrochloride is an α-1 adrenergic agonist drug that is used in ophthalmology mainly for its mydriatic effect. After topical application to the conjunctiva, Phenylephrine Hydrochloride acts directly on α-adrenergic receptors in the eye, producing contraction of the dilator muscle of the pupil and constriction of the arterioles in the conjunctiva.
How should I take Phenylephrine Hydrochloride?
Do not use if the solution turns brown or becomes cloudy.
To use:
- First, wash your hands. Tilt the head back and, pressing your finger gently on the skin just beneath the lower eyelid, pull the lower eyelid away from the eye to make a space. Drop the medicine into this space. Let go of the eyelid and gently close the eyes. Do not blink. Keep the eyes closed and apply pressure to the inner corner of the eye with your finger for 2 or 3 minutes to allow the medicine to be absorbed by the eye.
- Immediately after using the eye drops, wash your hands to remove any medicine that may be on them.
- To keep the medicine as germ-free as possible, do not touch the applicator tip to any surface (including the eye). Also, keep the container tightly closed.
For patients using the 2.5 or 10% eye drops:
- It is very important that you use Phenylephrine Hydrochloride only as directed. Do not use more of it and do not use it more often than your doctor ordered. To do so may increase the chance of too much medicine being absorbed into the body and the chance of side effects. This is especially important when Phenylephrine Hydrochloride is used in children or in patients with heart disease or high blood pressure, since high doses of Phenylephrine Hydrochloride may cause an irregular heartbeat and an increase in blood pressure.
Dosing
The dose of Phenylephrine Hydrochloride will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of Phenylephrine Hydrochloride. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For ophthalmic solution (eye drops) dosage form:
- For eye redness:
- Adults and children—Use one drop of 0.12% solution every three or four hours as needed.
- For eye exams:
- Adults and children—Use one drop of 2.5% solution. Depending on the eye test to be done, it will take from fifteen minutes to one or two hours for the medicine to work before you can have the eye test.
- For use before eye surgery:
- Adults and teenagers—Use one drop of 2.5 or 10% solution thirty to sixty minutes before the start of eye surgery.
- Children—Use one drop of 2.5% solution thirty to sixty minutes before the start of eye surgery.
- For certain eye conditions:
- Adults and teenagers—Depending on the eye condition being treated, your doctor may tell you to use one drop of 2.5 or 10% solution in the eye from once a day to three times a day.
- Children—Depending on the eye condition being treated, your doctor may tell you to use one drop of 2.5% solution in the eye from once a day to three times a day.
- For eye redness:
Missed Dose
If you miss a dose of Phenylephrine Hydrochloride, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
For non-prescription strength eye drops, follow the package directions.
Storage
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Phenylephrine Hydrochloride administration
IV:
Hypotension/shock: May be administered via continuous infusion (after diluting). When administering as a continuous infusion, central line administration is preferred. IV infusions require an infusion pump.
Hypotension during anesthesia: Administer as an IV bolus over 20 to 30 seconds.
Vesicant; ensure proper needle or catheter placement prior to and during infusion; avoid extravasation.
Extravasation management: If extravasation occurs, stop infusion immediately and disconnect (leave cannula/needle in place); gently aspirate extravasated solution (do NOT flush the line); remove needle/cannula; elevate extremity. Initiate phentolamine (or alternative antidote). Apply dry warm compresses (Hurst 2004; Reynolds 2014).
Phentolamine: Dilute 5 to 10 mg in 10 to 20 mL NS and administer into extravasation site as soon as possible after extravasation; may readminister if patient remains symptomatic (Reynolds 2014).
Alternative to phentolamine: Nitroglycerin topical 2% ointment (based on limited data): Apply a 1-inch strip to the site of ischemia; may repeat every 8 hours as necessary (Reynolds 2014).
Phenylephrine Hydrochloride pharmacology
Mechanism of Action
Phenylephrine Hydrochloride is an α-1 adrenergic agonist drug that is used in ophthalmology mainly for its mydriatic effect. After topical application to the conjunctiva, Phenylephrine Hydrochloride acts directly on α-adrenergic receptors in the eye, producing contraction of the dilator muscle of the pupil and constriction of the arterioles in the conjunctiva.
Pharmacodynamics
Maximal mydriasis occurs in 20 to 90 minutes with recovery after 3 to 8 hours.
Systemic absorption of sufficient quantities of Phenylephrine Hydrochloride may lead to systemic α-adrenergic effects, such as rise in blood pressure which may be accompanied by a reflex atropine-sensitive bradycardia.
Pharmacokinetics
The systemic exposure following topical administration of Phenylephrine Hydrochloride ophthalmic solution has not been studied. A higher systemic absorption is expected for the 10% solution than the 2.5% solution and when the corneal barrier function is compromised.
References
- NCIt. "Phenylephrine: NCI Thesaurus (NCIt) provides reference terminology for many systems. It covers vocabulary for clinical care, translational and basic research, and public information and administrative activities.". https://ncit.nci.nih.gov/ncitbrowser... (accessed September 17, 2018).
- EPA DSStox. "Phenylephrine: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).
- EPA Chemicals under the TSCA. "Benzenemethanol, 3-hydroxy-.alpha.-[(methylamino)methyl]- , hydrochloride (1:1), (.alpha.R)-: The Chemical Data Reporting under the Toxic Substances Control Act (TSCA) contains chemical physical description and chemical use categories.". http://www.epa.gov/chemical-data-rep... (accessed September 17, 2018).
Reviews
The results of a survey conducted on ndrugs.com for Phenylephrine Hydrochloride are given in detail below. The results of the survey conducted are based on the impressions and views of the website users and consumers taking Phenylephrine Hydrochloride. We implore you to kindly base your medical condition or therapeutic choices on the result or test conducted by a physician or licensed medical practitioners.User reports
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Information checked by Dr. Sachin Kumar, MD Pharmacology
