Histafen

Histafen (sequifenadine) is an antihistamine used to treat allergic reactions. Sequifenadine acts as an H1-histamine receptor blocker, helping to reduce symptoms caused by the release of histamine in the body, such as itching, runny nose, and eye irritation.

A study of the use of Histafen in patients with senile pruritus showed that the drug provided significant improvement in the condition of most patients, reducing the symptoms of pruritus and improving quality of life (Dyudyun & Polion, 2019).

Histafen may be an effective option for treating allergic reactions in patients who require histamine receptor blockade to reduce or prevent allergy symptoms.

Indications Histafen

1. Allergic rhinitis (hay fever): Histafen can help relieve nasal congestion, runny nose, sneezing and itchy nose caused by a reaction to pollen, dust, animal dander and other allergens.
2. Seasonal allergic rhinitis (hay fever): This medication may be used to treat symptoms caused by an allergic reaction to seasonal allergens such as grass and tree pollens.
3. Allergic conjunctivitis: Histafen may help reduce itchy, red, and watery eyes caused by allergic conjunctivitis, such as from contact with dust, pollen, or animals.
4. Hives (urticaria): This medication may be effective in relieving itching, redness, and swelling of the skin associated with hives or other allergic skin reactions.
5. Other allergic conditions: Histafen may also be used to treat other allergic conditions, including allergic reactions to insect bites, allergic dermatitis and allergic reactions to foods, provided that the drug has been prescribed by a doctor.

Release form

Histafen is usually available as a tablet for oral administration.

Pharmacodynamics

1. Mechanism of action:

   • Cetifenadine is an antihistamine that blocks peripheral H1-histamine receptors.
   • Histamine is a substance that is released in the body in response to an allergic reaction. Histamine can cause symptoms such as itching, runny nose, red eyes, and other signs of an allergic reaction.
   • Blocking H1-histamine receptors with cetifenadine prevents the action of histamine, which leads to a reduction or disappearance of allergic symptoms.

Pharmacokinetics

1. Absorption: Secyphenadine is generally well absorbed from the gastrointestinal tract after oral administration. Peak plasma concentrations are usually reached 2-4 hours after administration.
2. Metabolism: The primary metabolic pathway for secyphenadine is oxidation in the liver by cytochrome P450 3A4. The main metabolites are desloratadine and 3-hydroxydesloratadine. Desloratadine also has antihistamine properties and is used alone in the treatment of allergies.
3. Excretion: Secyphenadine metabolites and secyphenadine itself are excreted primarily in urine and feces. In healthy adults with full glomerular filtration coefficient, the pharmacokinetics of secyphenadine are not altered, but in patients with renal impairment (especially severe impairment), elimination may be delayed.
4. Half-life: The half-life of secyphenadine in the body is about 14 hours, which allows it to be taken once or twice a day, depending on the doctor's recommendations and the form of the drug.
5. Food effects: Food intake, particularly fatty foods, may delay the absorption of secipenadine but does not significantly affect its overall bioavailability.
6. Drug Interactions: Secyphenadine may interact with other drugs, including drugs metabolized through the cytochrome P450 3A4 system, such as macrolide antibiotics, protease inhibitors, and others.

Dosing and administration

1. Directions for use:

   • Histafen is usually taken orally, i.e. by mouth.
   • The tablets are usually swallowed whole with a small amount of water.
   • The drug can be taken regardless of food intake.

2. Dosage:

   • The dosage of Histafen may vary depending on the patient's age, weight and severity of allergy symptoms.
   • The usual recommended dose for adults and children over 12 years of age is 60 mg taken once daily.
   • For children aged 6 to 12 years, the usual recommended dose is 30 mg, also taken once daily.
   • For children aged 2 to 6 years, the usual recommended dose is 15 mg taken once daily.
   • For children under 2 years of age, it is recommended to consult a doctor before using Histafen.

3. Duration of admission:

   • The duration of taking Histafen is usually determined by the doctor depending on the nature and severity of the allergic symptoms.
   • The drug is usually taken for the duration of the patient's exposure to the allergen, but the decision on the duration of treatment should be made by the doctor.

Use Histafen during pregnancy

The use of sequifenadine (Histafen) during pregnancy is not recommended due to a lack of data on its safety for the developing fetus. Questions remain in the scientific literature regarding the effects of sequifenadine on pregnancy and fetal development.

Although direct studies of sequifenadine are limited, studies of other antihistamines such as terfenadine (a structural analogue of sequifenadine) have shown that use during pregnancy is not associated with an increased risk of major birth defects. However, studies have noted that infants exposed to terfenadine had slightly lower mean birth weights compared to controls (Loebstein et al., 1999).

Based on these data, it is recommended to avoid the use of sequifenadine during pregnancy, especially without consulting a physician who can evaluate the potential risks and benefits of its use depending on the individual clinical situation.

Contraindications

1. Hypersensitivity: People with known hypersensitivity to sequifenadine or any other ingredients of the drug should not take Histafen.
2. Use of CYP3A4 enzyme inhibitors: Use of sequifenadine in combination with CYP3A4 enzyme inhibitors such as ketoconazole or erythromycin may increase the blood levels of sequifenadine and increase the risk of cardiovascular side effects.
3. Increased risk of cardiovascular complications: Sequifenadine may increase the risk of cardiovascular complications, especially in people with heart disease, abnormal heart rhythms, or those taking other medications that may affect heart rhythm.
4. Pregnancy and breastfeeding: There is limited information on the safety of sequifenadine during pregnancy and breastfeeding, so its use during this period should only be carried out as prescribed by a doctor.
5. Paediatric use: Sequifenadine is not recommended for use in children under 6 years of age without consulting a doctor.
6. Hepatic impairment: Patients with severe hepatic impairment should avoid using sequifenadine or use it with caution under medical supervision.
7. Alcohol intake: Drinking alcohol while taking sequifenadine may increase some of its side effects, such as drowsiness and central nervous system depression.

Side effects Histafen

1. Drowsiness or tiredness: Some people may feel drowsy or tired after taking Histafen. This side effect may be increased by the simultaneous use of alcohol or other sedatives.
2. Dizziness: Some patients may experience dizziness or unsteadiness after taking the drug.
3. Dry mouth: Some people may experience dry mouth after taking Histafen.
4. Stomach upset: Stomach upset such as nausea, vomiting, diarrhea or constipation may occur.
5. Insomnia or anxiety: In some people, using Histafen may cause insomnia or anxiety.
6. Rare side effects: In rare cases, more serious side effects may occur, such as allergic reactions, muscle pain, weakness, or memory problems.

Overdose

Symptoms of a histafen overdose may include:

1. Drowsiness or fatigue.
2. Dizziness or unsteadiness.
3. Dry mouth.
4. Abdominal pain or discomfort in the stomach.
5. Rarely, more serious symptoms may occur, such as rapid heartbeat, difficulty breathing, or even seizures.

Interactions with other drugs

1. Drugs Metabolized via Cytochrome P450 3A4: Secifenadine is metabolized in the liver via the enzyme cytochrome P450 3A4. Drugs that are inhibitors or inducers of this enzyme may affect the metabolism of secifenadine. For example, cytochrome P450 3A4 inhibitors such as ketoconazole, erythromycin, or ritonavir may increase the concentration of secifenadine in the blood, which may lead to increased effects and an increased risk of adverse effects.
2. Alcohol: Drinking alcohol with secifenadine may enhance its sedative effects, causing increased drowsiness and lethargy.
3. Other centrally acting drugs: Secifenadine may enhance the sedative effects of other centrally acting drugs such as hypnotics, antianxiety drugs and antidepressants. This may lead to an increased risk of adverse effects such as drowsiness and lethargy.
4. Antihistamines: Using secifenadine with other antihistamines may increase their potency, which may also increase the risk of side effects.
5. Drugs that increase gastrointestinal pH: Drugs such as antacids or heartburn medications may affect the rate and extent of absorption of secifenadine from the gastrointestinal tract, which may decrease its effectiveness.