Mesaton

Mezaton is an α-adrenergic agonist; it has vasoconstrictive activity.

Indications Mesaton

It is used to eliminate ophthalmological disorders:

• iridocyclitis, anterior uveitis (therapy and prevention of the appearance of posterior adhesions or asthenopia, as well as reducing exudation associated with the iris);
• dilation of the pupil of the eye for diagnostic purposes during ophthalmoscopy and other procedures required to examine the condition of the posterior ocular region, as well as during laser procedures and vitreoretinal surgery;
• when performing provocative tests in individuals with a narrow view of the anterior chamber angle and a suspicion of developing closed-angle glaucoma;
• differential examination with intraocular injections;
• reducing irritation and hyperemia during red eye syndrome;
• combination therapy for accommodative spasm (children).

By parenteral administration in the following disorders:

• decreased blood pressure;
• state of shock (this includes its toxic and traumatic varieties);
• vascular insufficiency, sometimes developing in connection with intoxication with vasodilators;
• in the form of a vasoconstrictor for local anesthesia.

It can also be prescribed for intranasal administration for rhinitis of vasomotor or allergic origin.

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Release form

The pharmaceutical substance is released in the form of eye drops, inside dropper bottles with a capacity of 5 ml.

In addition, it is sold in the form of an injection liquid, inside ampoules with a capacity of 1 ml; a box contains 10 such ampoules.

Pharmacodynamics

Mezaton is an α-adrenergic stimulant with little effect on cardiac β-adrenergic receptors. It cannot be considered a catecholamine because the drug has only 1 hydroxyl category within its own aromatic nucleus; it can increase blood pressure and constrict arterioles, which sometimes causes reflex bradycardia.

Compared to epinephrine or norepinephrine, the drug increases blood pressure more smoothly, and its effect is longer lasting, because it is not so strongly affected by the component catechol-O-methyltransferase. Treatment with Mezaton does not cause an increase in the values of minute blood volume.

The drug has vasoconstrictive properties similar to the effect of norepinephrine, but the effect is less strong and longer lasting; at the same time, the drug does not have an inotropic or chronotropic effect on the heart.

Instillation of the drug leads to contraction of the pupillary dilator, as a result of which it expands (and along with it the smooth muscles of the conjunctival arterioles). The substance does not affect the activity of the ciliary muscle, due to which mydriasis is not accompanied by cycloplegia.

The medicinal effect develops immediately after intravenous injection and lasts for the next 5-20 minutes. If the substance is administered subcutaneously, the duration of the effect is 50 minutes, and with an intramuscular injection - 1-2 hours.

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Pharmacokinetics

Phenylephrine can easily penetrate into the eye tissues, dilating the pupil for 10-60 minutes. Significant reduction of the pupillary dilator in the fluid of the anterior chamber of the eye after 30-45 minutes after instillation allows detecting particles of the iris foliar pigment; in this case, it is necessary to differentiate uveitis or penetration of formed blood components.

Metabolic processes of phenylephrine develop inside the liver, and in addition, the gastrointestinal tract (the enzyme catechol-O-methyltransferase does not participate in this).

Excretion of metabolic elements occurs through the kidneys.

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Dosing and administration

Eye drops are used in the form of instillations - one drop must be instilled into the conjunctival sac of the eye.

The injection liquid is administered by jet or intravenously, at low speed.

In case of collapse.

Administration of the drug through a drip, intravenously - it is necessary to use a 1% liquid (1 ml), which is diluted in a 5% dextrose solution (0.25 or 0.5 l).

In this case, 0.1, 0.3 or 0.5 ml of 1% liquid is diluted in 5% dextrose solution (20 ml) or 0.9% NaCl. If necessary, the administration procedure can be repeated.

Dosage portions for intramuscular or subcutaneous administration (for adults) are in the range of 0.3-1 ml of 1% liquid, 2-3 times a day. Adolescents over 15 years of age (with reduced blood pressure) require 0.5-1 mg/kg of the patient's weight to perform spinal anesthesia.

To narrow the blood vessels inside the mucous membranes and reduce the intensity of inflammation symptoms, you need to instill or lubricate the area with concentrated liquid - 0.125, 0.25, as well as 0.5 or 1%.

Under local anesthesia.

To the anesthetic used in the form of a solvent (10 ml), it is necessary to add 0.3-0.5 ml of 1% liquid medicine.

Adults can be given a maximum of 10 mg of the substance per 1-time intramuscular or subcutaneous injection; a maximum of 50 mg of the drug per day. For intravenous injections, a single dose of the drug is a maximum of 5 mg, and a daily dose is 25 mg.

To prevent a recurrence of a decrease in blood pressure after discontinuing the medication, the dosage should be reduced gradually (especially if this is done after a prolonged infusion). Infusions may be resumed after systemic blood pressure has decreased to 70-80 mm Hg.

Use Mesaton during pregnancy

Mezaton may be used in pregnant women with great caution - in the presence of strict vital indications and under medical supervision (it is necessary to first assess the risks and benefits of the medication for the woman and the fetus).

At the same time, it was found that the introduction of vasoconstrictors during labor (to correct the decreased blood pressure), as well as additives to local anesthetics in combination with medications that stimulate uterine contractility (including ergotamine with vasopressin, as well as ergometrine with methylergometrine), can cause a persistent increase in blood pressure levels after labor.

Contraindications

Main contraindications:

• pheochromocytoma;
• hypertrophy associated with obstructive cardiomyopathy;
• ventricular fibrillation;
• the presence of intolerance associated with medicinal substances.

It is not prescribed for ophthalmological procedures in the following cases:

• glaucoma of a closed-angle or narrow-angle nature;
• significant disorders in the functioning of the cardiovascular system (including aneurysms, heart disease, tachycardia and high blood pressure);
• insulin-dependent type of diabetes mellitus;
• hyperthyroidism;
• the presence of disturbances in the integrity of the fundus of the eye or disorders of lacrimal activity;
• congenital deficiency of the G6PD component or hepatic porphyria.

Caution with the use of drugs is required in the following conditions:

• metabolic type of acidosis;
• hypoxia or hypercapnia;
• atrial fibrillation;
• increased blood pressure or hypertension within the pulmonary circulation of the systemic blood flow;
• hypovolemia;
• aortic stenosis of severe intensity;
• acute stage of myocardial infarction;
• ventricular arrhythmia or tachyarrhythmia;
• occlusive vascular pathology (also its presence in the anamnesis) during atherosclerosis, Raynaud's syndrome, thromboembolism of an arterial nature, Buerger's disease or diabetes mellitus, as well as with a vascular tendency to develop spasms, diabetic endarteritis and frostbite, as well as when combined with MAOIs;
• introduction of general anesthesia (fluorothane);
• renal dysfunction;
• elderly people.

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Side effects Mesaton

Side effects include:

• ventricular fibrillation, bradycardia, increased blood pressure, arrhythmia, palpitations and cardialgia;
• feeling of intense anxiety, fear or weakness, dizziness, insomnia, headaches;
• tremor, paresthesia, seizures, cerebral hemorrhage;
• paleness of the skin on the face;
• signs of allergy, local appearance of scab in case of penetration into tissues and epidermal ischemia in the area of drug administration.

When administering drops, negative symptoms may appear on the part of the visual organs: reactive hyperemia, a feeling of discomfort, burning or irritation, as well as visual blurring, reactive miosis, lacrimation and increased intraocular pressure.

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Overdose

In cases of poisoning, ventricular extrasystole, a feeling of heaviness in the extremities and head, as well as short-term paroxysmal symptoms of ventricular tachycardia and a significant increase in blood pressure are observed.

An intravenous injection of α-adrenoblockers is administered (phentolamine can be used). If cardiac arrhythmia occurs, it is recommended to administer β-adrenoblockers.

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Interactions with other drugs

Use together with antihypertensive and diuretic drugs leads to a weakening of the antihypertensive properties of these drugs (guanethidine, mecamylamine and guanadrel with methyldopa).

Combination with phenothiazines or α-blockers (such as phentolamine) reduces hypertensive activity.

The introduction in combination with MAOIs (including selegiline and furazolidone with procarbazine), as well as with ergot alkaloids, methylphenidate, oxytocin, and also tricyclics and adrenergic stimulants leads to a significant potentiation of pressor activity, as well as arrhythmogenicity of the phenylephrine element.

Combination with β-blockers weakens cardiac stimulating activity.

The use of reserpine leads to an increase in blood pressure, which develops due to the depletion of catecholamine depots located inside adrenergic receptors, as a result of which the reaction to adrenergic drugs increases.

Combined administration with anesthetics that are inhaled (including isoflurane, enflurane with methoxyflurane, as well as halothane and chloroform) increases the risk of developing severe arrhythmia affecting the atria or ventricles, because this sharply increases the sensitivity of the myocardium to sympathomimetics.

Use in combination with ergotamine, oxytocin or ergometrine, as well as doxapram or methylergometrine increases the intensity of the vasoconstrictive effect.

Administration together with nitrates weakens their antianginal activity, which reduces the pressor effect of sympathomimetics and creates a risk of decreased blood pressure.

With the simultaneous use of Mezaton and thyroid hormones, a mutual potentiation of their effects develops with the risk of developing coronary insufficiency, which is more likely in people with coronary atherosclerosis.

The mydriatic activity of phenylephrine is potentiated under the influence of atropine.

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Storage conditions

Mezaton should be kept in a dark place, out of reach of small children. Temperature values should not exceed +25°C.

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Shelf life

Mezaton in the form of injection liquid can be used for a 3-year period from the date of production of the therapeutic substance. The shelf life of drops is 24 months (after opening the bottle, it can be used for a maximum of 14 days).

Application for children

In pediatrics, it is prescribed with caution. Drops of the drug cannot be prescribed to newborn babies with low birth weight.

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Analogues

The following substances are analogs of the medication: Nazol Kids spray and Irifrin 2.5%.