Phenylephrine

Pharmacological properties

phenylephrine hydrochloride ((r) -hydroxy-alpha - [(methylamino) methyl] benzenemethanol hydrochloride) has a pronounced stimulating effect on postsynaptic α-adrenergic receptors, while the effect on cardiac ß-adrenergic receptors is almost not expressed. the drug has a vasoconstrictor effect, similar to the action of norepinephrine, however, it practically does not have a chronotropic and inotropic effect on the heart. the vasopressor effect of the drug is less pronounced than that of norepinephrine, but significantly longer. when used in usual doses, it does not have a significant stimulating effect on the central nervous system. after instillation, phenylephrine contracts the muscle dilator of the pupil, thereby causing its expansion, and the smooth muscles of the conjunctival arterioles. affects the ciliary muscle, so the mydriasis caused by the drug is not accompanied by cycloplegia.

Pharmacokinetics Phenylephrine easily penetrates into the tissues of the eye, pupil expansion occurs within 10-60 minutes after a single instillation. Mydriasis persists for 4–6 hours. Due to a significant reduction in the pupil dilator, pigment particles from the pigment sheet of the iris can be detected in the moisture of the anterior chamber 30–45 minutes after instillation. This phenomenon must be differentiated with manifestations of anterior uveitis or with the presence of blood cells in the moisture of the anterior chamber of the eye.

Indications

- iridocyclitis (in order to prevent the occurrence of posterior synechia and reduce exudation from the iris of the eye);

- diagnostic expansion of the pupil during ophthalmoscopy and other diagnostic procedures necessary to determine the condition of the posterior parts of the eye);

- conducting a provocation test in patients with a narrow profile of the angle of the anterior chamber of the eye and suspected closed-angle glaucoma;

- differential diagnosis of an eyeball injection type;

- preoperative expansion of the pupil (10% solution) in ophthalmic surgery;

- pupil expansion during laser interventions on the fundus and vitreoretinal surgery;

- glaucomocytic crisis;

- red eye syndrome - to reduce hyperemia and irritation of the membranes of the eye (2.5% rr);

- complex therapy of accommodation spasm;

- complex therapy of progressive myopia.

Application

Assign to adults and children over the age of 12 years.

When conducting ophthalmoscopy, a single instillation of 2.5% of solution is used. As a rule, to achieve mydriasis, it is sufficient to administer 1 drop of a 2.5% solution of the drug into the conjunctival sac. The maximum mydriasis is reached after 15-30 minutes and remains at a sufficient level for 1-3 hours. If it is necessary to maintain mydriasis for a long time, after 1 hour the drug can be reinstalled.

In adults and children over the age of 12 years with insufficient dilatation of the pupil, as well as in patients with rigid iris (pronounced pigmentation), 10% solution in the same doses is possible for the diagnostic expansion of the pupil.

For diagnostic procedures, a single installation of 2.5% solution is used:

- as a provocative test in patients with a narrow profile of the anterior chamber angle and suspected closed-angle glaucoma. If the difference between the values ​​of intraocular pressure before instillation of the drug and after the expansion of the pupil is from 3 to 5 mm RT. Art., a provocative test is considered positive;

- for differential diagnosis such as an eyeball injection: if, after 5 minutes after instillation, a narrowing of the vessels of the eyeball is noted, the injection is regarded as superficial.

While maintaining eye hyperemia, it is necessary to examine the patient for the presence of iridocyclitis or scleritis, as this indicates the expansion of blood vessels in deeper tissues of the eye.

With uveitis, 2.5% or 10% is used to prevent the development and rupture of the already formed posterior synechia, as well as to reduce exudation into the anterior chamber of the eye. For this purpose, one drop of the drug is instilled into the conjunctival sac of the affected eye (s) 2-3 times a day.

In glaucomyclic crisis, the vasoconstrictor effect of phenylephrine causes a hypotensive effect, which is more pronounced when using 10% solution. To prevent glaucomocyclic crises, 10% solution of the drug is instilled 2-3 times a day.

When preparing patients for surgical interventions 30-60 minutes before surgery, a single instillation of 10% solution is performed to achieve mydriasis. After opening the membranes of the eyeball, repeated instillations of the drug are not allowed!

Before using eye drops, remove the aluminum cap from the bottle, gently open the rubber stopper and put the attached dropper nozzle on the bottle, having previously removed it from the sealed wrapper. To carry out the instillation, remove the cap from the dropper nozzle, turn the bottle upside down and press on the soft surface of the dropper nozzle.

Contraindications

Narrow-angle or closed-angle glaucoma; advanced age, especially in the presence of significant disorders of the cardiovascular system or cerebrovascular pathology; additional dilatation of the pupil during surgery in patients with impaired eyeball integrity or with a violation of the function of lacrimation; hypersensitivity to any component of the drug; age up to 12 years; arterial aneurysm (for 10% solution); reduced body weight in children (for 2.5% solution); hyperthyroidism; hepatic porphyria; congenital deficiency of glucose-6-phosphate hydrogenase.

Side effects

In some cases, there is a burning sensation (at the beginning of use), blurred vision, irritation, discomfort, lacrimation, increased intraocular pressure, reactive miosis (the day after the use of the drug; in this case, repeated instillations may cause less pronounced mydriasis than the day before; the effect is more common manifested in elderly patients).

On the part of the cardiovascular system, tachycardia, arrhythmia, including ventricular, hypertension, reflex bradycardia, pulmonary embolism, coronary artery occlusion, myocardial infarction are possible (isolated cases have been reported when using 10% solution in elderly people with concomitant heart diseases -vascular system).

special instructions

There is no experience with the use of the drug during pregnancy and lactation. use is permissible if the predicted benefit to the mother outweighs the potential risk to the fetus or infant.

During the period of action of the drug, visual acuity decreases, so before you start driving or working with mechanisms, you must wait until visual acuity is fully restored.

Interactions

The mydriatic effect of phenylephrine is enhanced with topical administration of atropine. the use of 2.5% or 10% solution with MAO inhibitors, as well as within 21 days after the end of their use, should be carried out with caution, since systemic adrenergic effects may develop. the vasopressor action of adrenergic drugs can be potentiated by tricyclic antidepressants, propranolol, reserpine, guanethidine, methyldopa and m-anticholinergics. the use of 10% solution of the drug together with the systemic use of ß-adrenergic receptor blockers can lead to acute ag. the drug can potentiate the inhibition of cardiovascular activity with inhalation anesthesia.

Overdose

Symptoms: with an overdose, manifestations of the systemic effect of phenylephrine are possible.

Treatment: the use of α-adrenergic receptor blockers (for example, intravenous injection of phentolamine at a dose of 5-10 mg), if necessary, reapply.

Storage conditions

In the dark place at a temperature of no higher than 25 ° C. do not freeze! Shelf life after opening the bottle - 1 month.