Phenistil

INSTRUCTION FOR MEDICAL USE OF THE MEDICINAL PRODUCT Fenistil (Fenistil)

Composition:

Active substance: dimetindene maleate;

1 ml contains 1 mg of dimetindene maleate;

Excipients: sodium hydrogen phosphate, dodecahydrate; propylene glycol; benzoic acid E 210; disodium edetate; citric acid, monohydrate; sodium saccharin; purified water.

Pharmaceutical form. Oral drops.

Main physicochemical properties: clear solution, colorless or slightly brownish-yellow.

Pharmacotherapeutic group. Antihistamines for systemic use. ATC code R06A B03.

Pharmacological properties.

Pharmacodynamics.

Dimetindene maleate is a histamine antagonist at the H1-receptor level. At low concentrations, it exerts a stimulating effect on histamine methyltransferase, leading to histamine inactivation. It shows high affinity for H1-receptors and acts as a mast cell stabilizer. Dimetindene maleate has no effect on H2-receptors. It also possesses local anesthetic properties.

Dimetindene maleate is an antagonist of bradykinin, serotonin, and acetylcholine. It exists as a racemic mixture with R-(-)-dimetindene, which has more pronounced H1-antihistaminic activity.

Dimetindene maleate significantly reduces capillary permeability associated with immediate-type hypersensitivity reactions.

In combination with histamine H2-receptor antagonists, it inhibits virtually all histamine effects on the circulatory system.

Studies have shown that the effect of a single 4 mg dose of dimetindene in the form of drops on skin reactions persists up to 24 hours after administration.

Pharmacokinetics.

Systemic bioavailability of dimetindene in the form of drops is approximately 70%. After administration of the drops, maximum plasma concentration of dimetindene is reached within 2 hours.

At concentrations ranging from 0.09 to 2 μg/mL, plasma protein binding of dimetindene is approximately 90%. Metabolic reactions of dimetindene include hydroxylation and methoxylation.

The elimination half-life of dimetindene is nearly 6 hours. Dimetindene and its metabolites are excreted via the liver and kidneys.

Preclinical studies revealed no risk associated with the use of the drug at recommended doses. Dimetindene maleate showed no mutagenic or clastogenic properties.

Clinical characteristics

Indications.

Symptomatic treatment of allergic disorders: urticaria, seasonal (hay fever) and perennial allergic rhinitis, drug and food allergies.

Pruritus of various origins, except that associated with cholestasis. Pruritus associated with skin rashes such as chickenpox. Insect bites.

An adjunctive agent in eczema and other pruritic dermatoses of allergic origin.

Contraindications.

Hypersensitivity to dimethindene maleate or to any other component of the medicinal product. Duodenal/ pyloric stenosis.

Contraindicated in children under 1 month of age, especially premature infants.

Interaction with other medicinal products and other forms of interaction.

When used concomitantly with CNS depressants such as opioid analgesics, anticonvulsants, antidepressants (tricyclic antidepressants and monoamine oxidase inhibitors), other antihistamines, antiemetics, antipsychotics, anxiolytics, hypnotics, scopolamine, and ethanol, enhanced CNS depression may occur, which could lead to adverse effects or even life-threatening consequences.

Tricyclic antidepressants and anticholinergic agents, such as bronchodilators, gastrointestinal spasmolytics, mydriatics, and urological antimuscarinic agents, may produce an additive antimuscarinic effect when administered together with antihistamines, thereby increasing the risk of worsening glaucoma and urinary retention.

To minimize the risk of CNS depression or possible potentiation, concomitant administration of procarbazine and antihistamines should be performed with caution.

Special precautions for use

As with other antihistamines, caution should be exercised when using Fenistil in patients with glaucoma, bladder neck contracture and/or urinary retention, including those with benign prostatic hyperplasia, as well as in patients with chronic obstructive pulmonary diseases.

Like all H1-receptor antagonists and partially H2-receptor antagonists, this medication should be used with caution in patients with epilepsy. Antihistamines may cause excitation in young children.

The drug should be used with caution in elderly patients, in whom the risk of adverse reactions, including excitation and increased fatigue, is elevated. Avoid accidental use of the medication by elderly patients. Do not exceed the recommended dosage or duration of treatment without a physician's recommendation.

Use of the drop formulation should be cautious in children under 1 year of age: the sedative effect may be accompanied by episodes of nocturnal apnea. In young children, antihistamines may cause excitation.

Fenistil oral drops may be used in children aged 1 month to 1 year only upon a physician's recommendation and when there are clear indications for antihistamine therapy. The recommended dose must not be exceeded.

Use during pregnancy or breastfeeding

Pregnancy. Clinical data on the use of the drug in pregnant women are lacking. Animal studies have not shown any harmful effects (either direct or indirect) of the drug on the course of pregnancy, fetal development, or subsequent offspring development. However, during pregnancy, the drug should not be used except when the expected benefit outweighs the potential risk to the fetus. In such cases, the drug may be used only under a physician's supervision.

Breastfeeding. Dimetinden maleate is very likely to pass into breast milk. The drug is not recommended during breastfeeding. If treatment is necessary, breastfeeding should be discontinued for the duration of therapy.

Ability to affect reaction speed when driving or operating machinery

After taking Fenistil, delayed psychomotor reaction speed, drowsiness, and dizziness may occur; therefore, patients should refrain from driving vehicles or operating machinery.

Dosage and Administration

The duration of use of the medicinal product without medical consultation should not exceed 14 days.

Adults, children aged 12 years and older, and elderly patients.

The recommended daily dose is 3–6 mg, divided into 3 doses of 20–40 drops three times a day. For patients prone to drowsiness, it is recommended to administer 40 drops before bedtime and 20 drops in the morning during breakfast.

Dose adjustment is not required for elderly patients.

Children.

Administration of the medicinal product is recommended only after prior consultation with a physician. For children aged 1 month to 1 year, use is permitted only upon medical advice. The recommended daily dose is 0.1 mg (i.e., 2 drops) per kg of body weight per day, divided into 3 doses.

20 drops = 1 mL = 1 mg of dimetindene maleate.

Phenistil oral drops should not be exposed to high temperatures. They should be added directly to warm infant food immediately before feeding. If the child is fed with a spoon, the drops may be administered undiluted, using a teaspoon. The drops have a pleasant taste.

Children.

Do not administer to children under 1 month of age, especially premature infants. Use oral drops with caution in children under 1 year of age: sedative effects may be accompanied by episodes of nocturnal apnea. In younger children, antihistamine agents may cause excitation.

Phenistil oral drops may be used in children aged 1 month to 1 year only upon medical recommendation and when there are clear indications for antihistamine therapy. The recommended dose must not be exceeded.

Overdose.

In case of overdose of Phenistil oral drops, as with other antihistamine agents, the following symptoms may occur: central nervous system (CNS) depression and drowsiness (predominantly in adults), CNS stimulation and antimuscarinic effects (especially in children and elderly individuals), including excitement, ataxia, tachycardia, hallucinations, convulsions, tremor, pupil dilation, dry mouth, facial flushing, urinary retention, and fever. Subsequently, arterial hypotension, coma, and cardiorespiratory collapse may also develop.

In case of overdose, measures recommended by the healthcare facility should be taken, depending on the symptoms that occur.

Adverse reactions.

The main adverse effect associated with the use of the medicine is drowsiness, especially at the beginning of treatment. In very rare cases, allergic reactions may occur.

Possible adverse effects

Immune system disorders.

Rare: anaphylactic reactions, including facial swelling, pharyngeal swelling, rash; muscle spasms and dyspnea.

Psychiatric disorders.

Isolated cases: excitement.

Nervous system disorders.

Very common: increased fatigue.

Common: drowsiness, nervousness.

Isolated cases: headache, dizziness.

Gastrointestinal disorders.

Isolated cases: gastrointestinal disturbances, nausea, dryness of mouth and throat.

Shelf life. 2 years.

Storage conditions. Store in a place inaccessible to children, in the original cardboard packaging, at a temperature below 25 °C.

Packaging. 20 ml in a bottle with a dropper.

Availability. Over-the-counter (without prescription).

Manufacturer.

Haleon CH S.a.r.l. / Haleon CH S.a.r.l.

Manufacturer's address and address of its business operations.

Route De L’etraz 2, Nyon, 1260, Switzerland / Route De L’etraz 2, Nyon, 1260, Switzerland.