Usage
Ketotifen is prescribed for the prophylaxis of asthma and allergic conditions like allergic rhinitis and allergic conjunctivitis. It is classified as an antihistamine and mast cell stabilizer. Ketotifen’s mechanism of action involves blocking histamine H1 receptors and stabilizing mast cells, thereby preventing the release of inflammatory mediators like histamine and leukotrienes that contribute to allergic reactions and bronchospasm.
Alternate Names
Ketotifen fumarate (salt form)
Brand Names: Zaditen, Zaditor (ophthalmic), Alaway (ophthalmic), and various generics.
How It Works
Pharmacodynamics: Ketotifen exerts its therapeutic effects through a dual mechanism:
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H1-receptor antagonism: By blocking H1 receptors, ketotifen inhibits the effects of histamine, reducing symptoms like itching, sneezing, runny nose, and eye watering.
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Mast cell stabilization: Ketotifen prevents mast cell degranulation, inhibiting the release of histamine, leukotrienes, and other inflammatory mediators. This action helps prevent bronchospasm and reduces airway inflammation in asthma.
Pharmacokinetics:
- Absorption: Ketotifen is well-absorbed orally. Food may slightly delay absorption but doesn’t significantly affect bioavailability.
- Metabolism: Primarily metabolized in the liver, with a small fraction undergoing first-pass metabolism.
- Elimination: Excreted mainly through the kidneys, with a small portion eliminated in the feces. The elimination half-life is approximately 21 hours.
Mode of Action: Ketotifen binds to H1 receptors, preventing histamine from binding and triggering downstream effects. Its mast cell stabilization involves inhibiting calcium influx into mast cells, thus preventing degranulation.
Dosage
Standard Dosage
Adults: 1 mg twice daily (morning and evening). The dosage can be increased to 2 mg twice daily if needed. To minimize initial sedation, a gradual dose increase over the first week is recommended, starting with 0.5 mg twice daily or 1 mg once daily in the evening, then titrating up to the full dose.
Children:
- 6 months to 3 years: 0.05 mg/kg body weight twice daily (morning and evening). This is typically administered as 0.25 mL of syrup per kg of body weight.
- 3 years and older: 1 mg twice daily (morning and evening).
Special Cases:
- Elderly Patients: Dosage adjustments may be necessary based on individual patient response and renal/hepatic function. Start with a lower dose and monitor closely.
- Patients with Renal Impairment: Dose reduction may be required depending on the severity of renal impairment.
- Patients with Hepatic Dysfunction: Caution is advised, and dose adjustment may be considered in severe hepatic impairment.
- Patients with Comorbid Conditions: Ketotifen syrup contains carbohydrates and may require adjustments in patients with diabetes. Caution is warranted in patients with epilepsy, as it may lower the seizure threshold.
Clinical Use Cases
Ketotifen is primarily used for long-term prevention of asthma attacks and allergic symptoms. It is not indicated for the relief of acute asthma exacerbations. Patients experiencing acute attacks should use a rapid-onset bronchodilator like salbutamol. Ketotifen is not typically used in the specific clinical settings mentioned (intubation, surgical procedures, mechanical ventilation, ICU use, emergency situations).
Dosage Adjustments
Adjustments should be made based on patient-specific factors like renal or hepatic dysfunction, metabolic disorders, and patient response. Therapeutic drug monitoring might be helpful in some cases.
Side Effects
Common Side Effects:
Drowsiness, dry mouth, weight gain, increased appetite, headache, dizziness.
Rare but Serious Side Effects:
Severe allergic reactions (anaphylaxis), seizures (especially in children), hepatitis, thrombocytopenia.
Long-Term Effects:
Chronic complications are rare, but prolonged use may lead to weight gain.
Adverse Drug Reactions (ADR):
Any signs of hypersensitivity, seizures, or significant hepatic dysfunction require immediate attention.
Contraindications
- Hypersensitivity to ketotifen.
- Concurrent use with oral antidiabetic agents.
Drug Interactions
Ketotifen may potentiate the sedative effects of CNS depressants like alcohol, benzodiazepines, and opioids. It can also interact with certain antidiabetic medications.
Pregnancy and Breastfeeding
Pregnancy Safety Category C. Use with caution during pregnancy and breastfeeding, weighing potential benefits against risks.
Drug Profile Summary
- Mechanism of Action: H1-receptor antagonist and mast cell stabilizer.
- Side Effects: Drowsiness, dry mouth, weight gain, rarely seizures.
- Contraindications: Hypersensitivity, concurrent use with oral antidiabetics.
- Drug Interactions: CNS depressants, some antidiabetics.
- Pregnancy & Breastfeeding: Category C, use with caution.
- Dosage: Adults: 1 mg BID, Children (6 months-3 years): 0.05mg/kg BID, Children (3+ years): 1 mg BID.
- Monitoring Parameters: Asthma control, liver function tests, blood glucose (if applicable), weight.
Popular Combinations
Ketotifen is often used in conjunction with inhaled corticosteroids and bronchodilators for asthma management.
Precautions
Screen for allergies, epilepsy, diabetes, renal/hepatic dysfunction. Advise against alcohol and operating machinery if drowsiness occurs.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Ketotifen?
A: Adults: 1 mg BID, children (6mo-3yr): 0.05mg/kg BID, children (3yr+): 1 mg BID.
Q2: How long does it take for Ketotifen to reach full effectiveness?
A: Clinical effectiveness is generally reached after 2-3 months of continuous treatment.
Q3: Can Ketotifen be used to treat acute asthma attacks?
A: No, Ketotifen is for prophylactic use and not effective in treating acute asthma exacerbations. Patients should use a rescue inhaler (e.g., salbutamol).
Q4: What are the most common side effects of Ketotifen?
A: Drowsiness, dry mouth, increased appetite, and weight gain.
Q5: Are there any contraindications to using Ketotifen?
A: Hypersensitivity to ketotifen and concomitant use of oral antidiabetic agents.
Q6: Can Ketotifen be used during pregnancy or breastfeeding?
A: Pregnancy Category C. Use with caution, weighing benefits against risks. Discuss with the patient and consider alternative options if necessary.
Q7: Does Ketotifen interact with other medications?
A: Yes, it can potentiate the sedative effects of CNS depressants and interact with certain antidiabetic drugs.
Q8: What should patients be advised regarding lifestyle while taking Ketotifen?
A: Avoid alcohol and operating heavy machinery if drowsiness occurs. Monitor weight and blood glucose if applicable.
Q9: What monitoring parameters are essential during Ketotifen therapy?
A: Asthma control, liver function tests (periodically), weight, and blood glucose in diabetic patients.
