Vitrophen

Uses

Phenylephrine is an alpha-1 adrenergic agonist used in the management of hypotension, generally in the surgical setting associated with the use of anesthetics.

Phenylephrine injections are indicated to treat hypotension caused by shock or anesthesia, an ophthalmic formulation is indicated to dilate pupils and induce vasoconstriction, an intranasal formulation is used to treat congestion, and a topical formulation is used to treat hemorrhoids. Off-label uses include situations that require local blood flow restriction such as the treatment of priapism.

For mydriasis and cycloplegia for diagnostic procedure, for the treatment of acute and subacute iridocyclitis, chronic iridocyclitis, Adhesions and disruptions of iris and ciliary body, Sclera and iris operations

Vitrophen is also used to associated treatment for these conditions: Allergic Rhinitis (AR), Anorectal discomfort, Cold, Common Cold, Common Cold/Flu, Congestion of the Conjunctivas, Conjunctivitis allergic, Cough, Cough caused by Common Cold, Eye allergy, Eye redness, Fever, Flu caused by Influenza, Headache, Headache caused by Allergies, Headache caused by Common Cold, Headache caused by Pollen Allergy, Hemorrhoids, Hypotension, Irritative cough, Itching of the nose, Itching of the throat, Laryngotracheitis, Nasal Congestion, Nose discomfort, Ocular Inflammation, Ocular Irritation, Paroxysmal Supraventricular Tachycardia, Pollen Allergy, Respiratory tract congestion, Respiratory tract irritation, Rhinopharyngitis, Rhinorrhoea, Seasonal Allergies, Shock, Cardiogenic, Sinus Congestion, Sinus pressure, Sinusitis, Sneezing, Sore Throat, Tracheobronchitis, Upper respiratory tract hypersensitivity reaction, site unspecified, Vasomotor Rhinitis, Aching caused by Flu caused by Influenza, Bronchial congestion, Itchy throat, Minor aches and pains, Watery itchy eyes, Airway secretion clearance therapy, Antihistamine, Dilatation of the pupil, Vasoconstrictor in regional analgesia therapyDiagnostic procedures

How Vitrophen works

Phenylephrine is an alpha-1 adrenergic agonist that mediates vasoconstriction and mydriasis depending on the route and location of administration. Systemic exposure to phenylephrine also leads to agonism of alpha-1 adrenergic receptors, raising systolic and diastolic pressure as well as peripheral vascular resistance. Increased blood pressure stimulates the vagus nerve, causing reflex bradycardia.

Muscarinic acetylcholine receptors are involved in numerous ocular functions. The M₃ subtype is predominantly expressed by smooth muscle cells of the sphincter pupillae, which is a circular muscle of the iris, and ciliary muscles. In response to light or binding of acetylcholine, M₃ receptor signalling leads to contraction of the sphincter pupillae and pupil constriction. Contraction of the ciliary muscle via M₃ receptor signalling also leads to accommodation, adjusting the lens for near vision. The eye is also innervated by parasympathetic nerves: ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction.

Tropicamide is a non-selective muscarinic antagonist that binds to all subtypes of muscarinic receptors. By binding to muscarinic receptors, tropicamide relaxes the pupillary sphincter muscle and causes pupil dilation. By blocking the muscarinic receptors of the ciliary body, tropicamide also prevents accommodation. Like other muscarinic antagonists, tropicamide inhibits the parasympathetic drive, allowing the sympathetic nervous system responses to dominate. Tropicamide is thought to ameliorate sialorrhea by blocking M₄ receptors expressed on salivary glands and reducing hypersalivation.

Dosage

Vitrophen dosage

For refraction:Instill one or two drops of 1% solution in the eye(s), repeated in five minutes. If patient is not seen within 20 to 30 minutes, an additional drop may be instilled to prolong mydriatic effect.

For examination of fundus:instill one or two drops of 0.5% solution 15 to 20 minutes prior to examination. Individuals with heavily pigmented irides may require higher strength or more doses.

Side Effects

Transient stinging, blurred vision, photophobia and superficial punctate keratitis have been reported with the use of tropicamide. Increased intraocular pressure has been reported following the use of mydriatics. Dryness of the mouth, tachycardia, headache, allergic reactions, nausea, vomiting, pallor, central nervous system disturbances and muscle rigidity have been reported with the use of tropicamide.

Toxicity

Patients experiencing and overdose may present with headache, hypertension, reflex bradycardia, tingling limbs, cardiac arrhythmias, and a feeling of fullness in the head. Overdose may be treated by supportive care and discontinuing phenylephrine, chronotropic medications, and vasodilators. Subcutaneous phentolamine may be used to treat tissue extravasation.

Oral LD₅₀ is 865 mg/kg in rats and 565 mg/kg in mice. Intraperitoneal LD₅₀ is 1210 mg/kg in rats and 695 mg/kg in mice. Subcutaneous LD₅₀ is 872 mg/kg in rats and 665 mg/kg in mice.

There is limited information on tropicamide overdose. Systemic adverse effects, such as tachycardia, central nervous system disturbances, and muscle rigidity have been reported with the use of tropicamide. Psychotic reactions, behavioral disturbances, and vasomotor or cardio-respiratory collapse have been reported with the use of anticholinergic in children.

Precaution

The lacrimal sac should be compressed by digital pressure for 2-3 minutes after instillation to avoid excessive systemic absorption.

Interaction

Tropicamide may interfere with the antihypertensive action of carbachol, pilocarpine, or ophthalmic cholinesterase inhibitors.

Volume of Distribution

The volume of distribution of phenylephrine is 340L.

No information can be found.

Elimination Route

Phenylephrine is 38% orally bioavailable. Clinically significant systemic absorption of ophthalmic formulations is possible, especially at higher strengths and when the cornea is damaged.

Following ocular administration of 40 μL drops of 0.5% tropicamide in female subjects, tropicamide reached its mean peak concentration in plasma of 2.8 ± 1.7 ng/mL (mean ± SD) at five minutes.

Half Life

Intravenous phenylephrine has an effective half life of 5 minutes and an elimination half life of 2.5 hours.

Tropicamide has a plasma half-life of 30 minutes.

Clearance

Phenylephrine has an average clearance of 2100mL/min.

No information can be found.

Elimination Route

86% of a dose of phenylephrine is recovered in the urine with 16% as the unmetabolized drug, 57% as the inactive meta-hydroxymendelic acid, and 8% as inactive sulfate conjugates.

No information can be found.

Pregnancy & Breastfeeding use

Pregnancy Category C. Tropicamide should be given to a pregnant woman only if clearly needed. It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when tropicamide is administered to a nursing woman.

Contraindication

Contraindicated in persons showing hypersensitivity to any component of Tropicamide.

Storage Condition

Store at 15° to 25°C . Do not refrigerate or store at high temperatures. Keep container tightly closed.

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