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Ketotifen is used to prevent bronchial asthma. So what is the effect of Ketotifen and how should it be used?
1. What is Ketotifen?
Ketotifen is an active substance belonging to the group of H1 antihistamines with effective anti-allergic effects. Ketotifen has the following dosage forms and strengths:
Ketotifen 1mg tablet/capsule; Eye drop solution with concentrations of 1.25mg/5ml, 0.25mg/ml and 2.5mg/ml; Syrup 0.2mg/ml.
2. Pharmacological characteristics of the drug Ketotifen
2.1. Pharmacodynamics Ketotifen is an active H1-receptor blocker of histamine with non-competitive, relatively selective and mast cell protective effects. The oral form of Ketotifen, which acts primarily on the respiratory system, is considered a non-bronchodilator and antiallergic agent for asthma. Ketotifen's primary mechanism of action is to inhibit the release of allergenic chemical mediators from mast cells and cells involved in allergic reactions, including histamine, leukotrienes C4, D4, and PAF.
Ketotifen's ability to inhibit H1 receptors of histamine and inhibit phosphodiesterase enzymes has some effects as follows:
Stimulates increased cAMP content in mast cells; Prevention of the development of allergic reactions on the respiratory tract; Inhibition of platelet activation by PAF (platelet activating factor) or by nerve excitations following administration of sympathomimetic drugs; Preventing eosinophil cells and platelets from collecting on the respiratory tract due to the influence of PAF; Inhibits eosinophil proliferation, thereby preventing eosinophil cell influx to the site of inflammation. The long-term efficacy of Ketotifen in pediatric patients with mild allergic bronchial asthma has been demonstrated in clinical trials. Continuous daily treatment with Ketotifen reduces the frequency, severity, and duration of asthma symptoms, while also helping to reduce the need for daily asthma medications (eg, theophylline, agonists). B2...) without affecting respiratory lung function (such as FEV1, FVC and PEFR index).
2.2. Pharmacokinetics Absorption: Ketotifen after oral administration is well absorbed from the gastrointestinal tract (over 60%). However, bioavailability is only about 50% due to first-pass metabolism by the liver. Peak plasma concentrations are reached 2 - 4 hours after dosing, the half-life is about 1 hour; Distribution: Approximately 75% of the active substance Ketotifen is bound to plasma proteins; Metabolism: Ketotifen undergoes relatively high first-pass metabolism (approximately 50%). The metabolite of Ketotifen in plasma and urine is Ketotifen-N-glucuronide; Elimination: Ketotifen is eliminated primarily in the urine as unchanged drug (approximately 1%) and inactive metabolites (60-70%) within 48 hours. The half-life is about 21 hours.
3. Indications and contraindications of Ketotifen
3.1. Indications Prevention of all forms of bronchial asthma (including asthma alone, asthma in case of seasonal fever and allergic bronchitis). When starting treatment with Ketotifen, the patient must still maintain basic asthma medications such as bronchodilators, theophylline or corticosteroids; Treatment of symptoms caused by allergic rhinitis, systemic allergic conditions, urticaria, rash, atopic dermatitis or allergic conjunctivitis. Note: Ketotifen is not used in the treatment of acute asthma attacks.
3.2. Contraindications of Ketotifen History of allergy or hypersensitivity to Ketotifen and other components of the drug; Women in the first 3 months of pregnancy or breastfeeding.
4. How to use and dose Ketotifen
4.1. Ketotifen tablet form 1mg Adults, adolescents and children over 3 years old: In the first 3-4 days, take 1 tablet of Ketotifen 1mg once only in the evening with food. The following days take Ketotifen 1mg 2 times / day, 1 tablet each time in the morning and evening when eating; For adults and children over 10 years old: If after 4 weeks of treatment is not effective, the maximum dose can be increased to 2mg/time, 2 times/day. Children 6 months to under 3 years old: Can use 0.5mg / time, 2 times a day (recommended to use syrup form instead of tablets to take). Children who are sensitive to the sedative effects of Ketotifen should start with 1⁄2 doses in the evening for the first few days of treatment and then increase the dose gradually. Ketotifen eye drops form:
Adults and children 3 years of age and older: 1 drop each, 2 times a day, can be repeated after 8 to 12 hours but no more than 2 eye drops a day; The form of eye drops should not be used in children under 3 years of age.
5. Ketotifen side effects
Some common undesirable effects of Ketotifen are:
Eye irritation or pain; Perforation keratitis; Erosion of the corneal epithelium. Less common side effects of Ketotifen:
Blurred vision (as eye drops), dry eyes; Eyelid disorders; Conjunctivitis; Photophobia; Conjunctival hemorrhage; Dry mouth ; lethargy; Urticaria, eczema or rash. Some rare side effects:
Headache; Hypersensitivity reactions: Including local reactions (such as contact dermatitis, eye swelling, eyelid itching and edema), systemic reactions (including swelling/oedema of the face or exacerbation of allergic disease). available as asthma and eczema).
6. Notes when using Ketotifen
6.1. General Notes Do not suddenly stop using medicines to treat symptoms or prevent asthma attacks when starting Ketotifen .
Note when using Ketotifen eye drops:
May cause eye irritation, especially when accompanied by dry eyes or corneal disorders; Contact lenses should be removed before instillation, do not re-insert lenses early, but need to leave for about 15 minutes for Ketotifen to contact the eyes; Do not let the dropper tip of Ketotifen eye drops directly touch your eyes; Use up to 30 days after opening the vial. 6.2. Note to pregnant women Ketotifen drug is classified as pregnancy category C, so it should be used with caution when prescribed to pregnant women.
6.3. Caution for lactating women Caution should be exercised when Ketotifen is used in lactating women.
6.4. Note when driving and operating machinery Any case of experiencing Ketotifen side effects such as temporary blurred vision, visual disturbances or drowsiness, absolutely do not drive or operate machinery.
6.5. Ketotifen Overdose and Management Symptoms of Ketotifen overdose may include confusion, disorientation, increased heart rate, hypotension, convulsions, sensitivity to stimuli (especially in children) and /or reversible coma.
Treatment of overdose:
If you have just taken Ketotifen, you can consider performing gastric lavage or using activated charcoal; Other supportive treatments are indicated depending on the patient's symptoms; The active ingredient Physostigmine can be used for the purpose of minimizing anticholinergic effects; Short-acting barbiturates or benzodiazepines can be used when the patient presents with agitation or convulsions.
7. Drug Interactions of Ketotifen
Ketotifen may interfere with the effect of other pain relievers or antihistamines when used concurrently; Oral administration of Ketotifen fumarate during the diet may lead to thrombocytopenia. With eye drops there have been no reports of this interaction; The drugs Acarbose, Acetohexamide, Alogliptin, Canagliflozin, Dapagliflozin, Chlorpropamide when combined with Ketotifen may increase the risk of serious thrombocytopenia; Amphetamine, Benzphetamine may reduce the sedative and stimulant effects of Ketotifen; Betahistine reduces the therapeutic effect of Ketotifen when used in combination.
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