Actions of Vistafrin in details
In general, α1-adrenergic receptors mediate contraction and hypertrophic growth of smooth muscle cells. α1-receptors are 7-transmembrane domain receptors coupled to G proteins, Gq/11. Three α1-receptor subtypes, which share approximately 75% homology in their transmembrane domains, have been identified: α1A (chromosome 8), α1B (chromosome 5), and α1D (chromosome 20). Vistafrin appears to act similarly on all three receptor subtypes. All three receptor subtypes appear to be involved in maintaining vascular tone. The α1A-receptor maintains basal vascular tone while the α1B-receptor mediates the vasocontrictory effects of exogenous α1-agonists. Activation of the α1-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. Vistafrin produces its local and systemic actions by acting on α1-adrenergic receptors peripheral vascular smooth muscle. Stimulation of the α1-adrenergic receptors results in contraction arteriolar smooth muscle in the periphery. Vistafrin decreases nasal congestion by acting on α1-adrenergic receptors in the arterioles of the nasal mucosa to produce constriction; this leads to decreased edema and increased drainage of the sinus cavities.
How should I take Vistafrin?
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 Vistafrin 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 Vistafrin is used in children or in patients with heart disease or high blood pressure, since high doses of Vistafrin may cause an irregular heartbeat and an increase in blood pressure.
Dosing
The dose of Vistafrin 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 Vistafrin. 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 Vistafrin, 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.
Vistafrin 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).
Vistafrin pharmacology
Mechanism Of Action
Vistafrin is an a-1 adrenergic receptor agonist.
Pharmacodynamics
Interaction of Vistafrin with a1-adrenergic receptors on vascular smooth muscle cells causes activation of the cells and results in vasoconstriction. Following Vistafrin intravenous administration, increases in systolic and diastolic blood pressures, mean arterial blood pressure, and total peripheral vascular resistance are observed. The onset of blood pressure increase following an intravenous bolus Vistafrin administration is rapid, typically within minutes. As blood pressure increases following intravenous administration, vagal activity also increases, resulting in reflex bradycardia.
Vistafrin has activity on most vascular beds, including renal, pulmonary, and splanchnic arteries.
Pharmacokinetics
Following an intravenous infusion of Vistafrin, the observed effective halflife was approximately 5 minutes. The steady-state volume of distribution of approximately 340 L suggests a high distribution into organs and peripheral tissues. The average total serum clearance is approximately 2100 mL/min. The observed Vistafrin plasma terminal elimination half-life was 2.5 hours.
Vistafrin is metabolized primarily by monoamine oxidase and sulfotransferase. After intravenous administration of radiolabeled Vistafrin, approximately 80% of the total dose was eliminated within first 12 h; and approximately 86% of the total dose was recovered in the urine within 48 h. The excreted unchanged parent drug was 16% of the total dose in the urine at 48 h post intravenous administration. There are two major metabolites, with approximately 57 and 8% of the total dose excreted as m-hydroxymandelic acid and sulfate conjugates, respectively. The metabolites are considered not pharmacologically active.
Clinical Studies
The evidence for the efficacy of Vistafrin is derived from studies of Vistafrin in the published literature. The literature support includes 16 studies evaluating the use of intravenous Vistafrin to treat hypotension during anesthesia. The 16 studies include 9 studies where Vistafrin was used in low-risk (ASA 1 and 2) pregnant women undergoing neuraxial anesthesia during Cesarean delivery, 6 studies in non-obstetric surgery under general anesthesia, and 1 study in non-obstetric surgery under combined general and neuraxial anesthesia. Vistafrin has been shown to raise systolic and mean blood pressure when administered either as a bolus dose or by continuous infusion following the development of hypotension during anesthesia.
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 Vistafrin 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 Vistafrin. 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
Consumer reported administration
No survey data has been collected yetConsumer reviews
There are no reviews yet. Be the first to write one! |
Information checked by Dr. Sachin Kumar, MD Pharmacology