Usage
Loratadine is prescribed for the symptomatic relief of allergic conditions such as:
- Allergic rhinitis (hay fever): including symptoms like sneezing, runny nose, itchy or watery eyes, and itching of the nose or throat.
- Chronic idiopathic urticaria (hives): characterized by itchy, raised welts on the skin.
- Other allergic reactions: such as reactions to insect bites and stings and some food allergies.
Pharmacological Classification: Loratadine is a second-generation antihistamine. More specifically it’s a long-acting tricyclic antihistamine.
Mechanism of Action: Loratadine acts as a selective inverse agonist of peripheral histamine H1 receptors. This means it blocks the action of histamine, a chemical released by the body during an allergic reaction that causes the typical allergy symptoms. It is considered a non-sedating antihistamine because it poorly penetrates the blood-brain barrier, minimizing its effects on the central nervous system.
Alternate Names
Loratadine is the generic name. It’s also known as the INN (International Nonproprietary Name).
Brand Names: Some popular brand names for loratadine include Claritin, Alavert, and others.
How It Works
Pharmacodynamics: Loratadine primarily works by blocking the effects of histamine at peripheral H1 receptors. It reduces vascular permeability, decreases itching, and diminishes other allergy symptoms. It demonstrates dose-related inhibition of histamine-induced skin reactions. Its effect is rapid in onset, typically within 1–4 hours, reaches peak effectiveness between 8–12 hours, and can persist for up to 24 hours. It is a non-sedating antihistamine.
Pharmacokinetics:
- Absorption: Loratadine is rapidly absorbed after oral administration.
- Metabolism: It is extensively metabolized in the liver, primarily by CYP3A4 and CYP2D6 enzymes, to its active metabolite, descarboethoxyloratadine (desloratadine).
- Elimination: Both loratadine and its metabolite are excreted in urine and feces, with an elimination half-life of approximately 8 hours for loratadine and about 28 hours for desloratadine.
Mode of Action: Loratadine binds to and stabilizes the inactive state of the H1 receptor, preventing histamine from binding and triggering the allergic cascade.
Receptor Binding: Selective inverse agonist at peripheral H1 receptors.
Enzyme Inhibition/Neurotransmitter Modulation: No significant direct effects on other enzymes or neurotransmitters besides its impact on histamine pathways.
Elimination Pathways: Primarily hepatic metabolism via CYP3A4 and CYP2D6 followed by renal and fecal excretion.
Dosage
Standard Dosage
Adults:
- 10 mg orally once daily. The maximum recommended dose is 10 mg per 24 hours.
Children:
- 2-5 years: 5 mg orally once daily (usually as a syrup or oral solution).
- 6-11 years (weighing more than 30 kg): 10 mg orally once daily.
- Children under 2 years: Safety and efficacy not fully established; use with caution and only as directed by a physician.
Special Cases:
- Elderly Patients: No specific dosage adjustments are typically required, but start with a lower dose and monitor for side effects.
- Patients with Renal Impairment: No dosage adjustments are generally necessary.
- Patients with Hepatic Dysfunction:
- Reduced clearance of loratadine may occur; initiate with a lower dose of 10 mg every other day for adults and children over 30 kg or 5 mg every other day for children 2-5 years old.
- Patients with Comorbid Conditions: Consider individual patient factors and adjust dosage accordingly if necessary. Consult a specialist if needed.
Clinical Use Cases
Loratadine is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. It is primarily indicated for outpatient management of allergic rhinitis and chronic idiopathic urticaria.
Dosage Adjustments
Dose modifications may be necessary for patients with severe hepatic impairment, generally starting at a lower dose and titrating upwards as needed based on individual patient response and tolerance.
Side Effects
Common Side Effects:
- Headache
- Somnolence (drowsiness), though less common than with first-generation antihistamines
- Fatigue, especially in children
- Dry mouth
- Nervousness, mainly in children
Rare but Serious Side Effects:
- Allergic reactions (anaphylaxis, angioedema)
- Hepatic dysfunction
- Tachycardia, palpitations
- Seizures
Long-Term Effects: Limited data on long-term effects are available; however, no significant long-term side effects have been reported.
Contraindications
- Hypersensitivity to loratadine or any of its components.
Drug Interactions
- CYP3A4 and CYP2D6 inhibitors: May increase plasma concentrations of loratadine, potentially raising the risk of side effects. Monitor patients closely.
- Alcohol: Concomitant use can enhance the sedative effects of loratadine. Advise patients to avoid or limit alcohol consumption while taking this medication.
- Other CNS depressants: Additive sedative effects may occur. Exercise caution when prescribing with other medications that depress the central nervous system.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Data on loratadine use during pregnancy are limited, and its safety has not been fully established. Use cautiously and only if clearly needed.
- Breastfeeding: Loratadine is excreted in breast milk. Consider the risks and benefits before using in breastfeeding mothers. Alternative options may be considered if necessary.
Drug Profile Summary
- Mechanism of Action: Selective inverse agonist at peripheral H1 receptors.
- Side Effects: Common: Headache, somnolence, fatigue, dry mouth. Serious (rare): Allergic reactions, hepatic dysfunction, tachycardia, seizures.
- Contraindications: Hypersensitivity.
- Drug Interactions: CYP3A4/2D6 inhibitors, alcohol, CNS depressants.
- Pregnancy & Breastfeeding: Use with caution if benefits outweigh risks.
- Dosage: Adults: 10 mg once daily. Children (2-5 years): 5 mg once daily. Children (6+ years and >30 kg): 10 mg once daily.
- Monitoring Parameters: Monitor for allergic reactions, hepatic function (if concerns exist), and any unusual side effects.
Popular Combinations
Loratadine is sometimes combined with pseudoephedrine (a decongestant) in products like Claritin-D to treat allergy symptoms accompanied by nasal congestion. However, these combinations are typically not recommended for patients with certain conditions like severe hypertension or coronary artery disease.
Precautions
- General Precautions: Evaluate for hypersensitivity to loratadine or any other ingredients before initiating therapy.
- Specific Populations: Use with caution in patients with severe hepatic impairment. Caution advised during pregnancy and breastfeeding.
- Lifestyle Considerations: Avoid alcohol as it may potentiate drowsiness. Caution when driving or operating machinery until individual response is known.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Loratadine?
A: Adults and children 6 years and older weighing more than 30 kg: 10 mg once daily. Children 2-5 years of age: 5 mg once daily.
Q2: How does Loratadine work?
A: Loratadine blocks the action of histamine at peripheral H1 receptors, thereby relieving allergy symptoms.
Q3: What are the common side effects of Loratadine?
A: Common side effects include headache, drowsiness, fatigue, and dry mouth.
Q4: Is Loratadine safe during pregnancy?
A: Limited safety data are available during pregnancy. Use with caution if benefits outweigh risks.
Q5: Can I take Loratadine with alcohol?
A: Alcohol may potentiate the sedative effects of Loratadine. It’s best to avoid or limit alcohol while taking this medication.
Q6: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember, unless it’s almost time for the next dose. Do not double the dose to catch up.
Q7: Are there any drug interactions I should be aware of?
A: Interactions may occur with CYP3A4/2D6 inhibitors and other CNS depressants. Consult with a physician or pharmacist about potential interactions with your other medications.
Q8: How long does it take for Loratadine to work?
A: Loratadine typically starts working within 1-4 hours, with peak effects between 8-12 hours.
Q9: What are some other brand names for loratadine?
A: Claritin and Alavert are examples of brand names for loratadine.
