Loratadine

Article Author:
Gursharan Sidhu
Article Editor:
Hossein Akhondi
Updated:
6/12/2019 9:31:57 PM
PubMed Link:
Loratadine

Indications

Loratadine is an FDA-approved medication for the relief and treatment of allergic rhinitis (hay fever) and urticaria (allergic skin rash). Loratadine is an effective, second-generation antihistamine that may be used in a variety of conditions to relief pruritus, watery eyes, runny nose, and sneezing associated with seasonal allergies. Loratadine is available as a prescription by the patient's primary care physician, but it is also available as an over-the-counter medication. Loratadine is safe to use in the geriatric population and children over the age of two.[1][2][3]

Mechanism of Action

Loratadine is a long-acting, non-sedating tricyclic antihistamine (piperidine derivative) with selective antagonistic properties to peripheral histamine H1-receptors. Loratadine selectively works to inhibit H1-receptors primarily located on respiratory smooth muscle cells, vascular endothelial cells, the gastrointestinal tract, and immune cells. Unlike the first-generation antihistamines such as diphenhydramine, loratadine is a competitive histamine antagonist that does not cross the blood-brain barrier. Therefore, it does not affect the neurons of the central nervous system, thereby preventing daytime somnolence or sedation. Loratadine binds to H1-receptors in different cells and causes a decrease in vascular permeability (prevents edema and flushing), decreases smooth muscle tone (bronchodilation) and decreases the activation of the peripheral nociceptive receptors (decreases pain and pruritus). At high concentrations, second-generation antihistamines such as Loratadine can inhibit histamine release from mast cells and basophils, thereby decreasing ICAM-1 expression in epithelial cells and inhibiting type 1 hypersensitivity reactions (e.g., hay fever, urticaria, pruritus, edema).[4][5][6] 

Loratadine has a fast onset of action; works within 1 to 3 hours, and its effects peak within 8 to 12 hours and elimination is through the fecal and renal routes. Metabolism is primarily in the liver into its active metabolite, descarboethoxy-loratadine via the CYP3A4 pathway.

Administration

Loratadine dosing is by tablet (chewable or disintegrating), capsule, or syrup (5mg/mL solution). The medication can be administered orally with or without meals. The dispersible tablet is to be placed in the mouth and allowed to dissolve. The patient may swallow it with or without water.

For allergic rhinitis:

  • In adolescents, adults, and geriatrics: 10mg PO daily or 5mg BID; do not exceed 10mg in 24 hours
  • In pediatrics: Age 2 to 6, 5mg PO QDay; over the age of 6, 10mg PO daily

For urticaria:

  • In adolescents, adults, and geriatrics: 10mg PO daily; do not exceed 10mg in 24 hours
  • In pediatrics: Over the age of 6, 10mg PO daily

Patients with renal impairment (GFR of less than 30mL/min): 

  • In adults; 10mg PO every other day
  • In children age 2 to 6; 5mg PO every other day
  • In children over the age of 6; 10mg PO every other day

Patients with hepatic impairment:

  • In adults; 10mg PO every other day
  • In children age 2 to 6; 5mg PO every other day
  • In children over the age of 6; 10mg PO every other day

Adverse Effects

Though loratadine is a relatively safe and effective medication for the treatment of allergic rhinitis, its primary adverse effects include headaches, dizziness, and GI distress (diarrhea, abdominal pain, nausea, and vomiting). Loratadine may also cause sedation (rare side effect), mydriasis, and xerostomia due to the anticholinergic effects.[7][8] 

Patients should not take loratadine with other CNS depressants such as diphenhydramine, dextromethorphan, or pseudoephedrine as it may cause dose-related sedation. 

Contraindications

Contraindications to loratadine include patients with documented hypersensitivity to the drug or components of the formulation, with strong contraindications in children under the age of 2 due to its antihistamine properties, which may cause CNS stimulation or seizures in young patients.

This medication requires cautious use in asthmatic or COPD patients due to its anticholinergic effects, which may cause a flare-up. 

Though the medication is generally non-sedating, patients that perform activities that require concentration such as maneuvering a motor vehicle should be advised to use caution as it may cause some drowsiness.

Patients diagnosed with phenylketonuria (PKU) are advised to speak with their primary care physician before taking loratadine as some of its formulations (e.g., orally disintegrating tablets) may contain phenylalanine, which may exacerbate the symptoms of PKU. 

Patients with liver disease or hepatic impairment are advised to use caution as the liver extensively metabolizes loratadine and dose adjustments are necessary per healthcare guidelines. Similarly, individuals with kidney failure or renal impairment should be cautious as such patients will have elevated loratadine concentrations, requiring dose adjustments.[9][10]

Breastfeeding mothers should consult their healthcare provider before use, as the medication gets excreted into breast milk. Additionally, per the American College of Obstetricians and Gynecologists self-medicating with loratadine in pregnant women is not advisable specifically during the first trimester.  

Monitoring

Patients taking loratadine require monitoring for the relief of symptoms, sedation, and any anticholinergic effects (such as dilated pupils and drying of oral mucosa). 

The renal and hepatic function also require close monitoring by the primary care physician for patients with kidney or liver impairment, with appropriate dose adjustment of the drug made accordingly. 

Cardiac function should also be monitored in individuals with a history of cardiac arrhythmias to prevent loratadine over-medication. 

Loratadine should be stored in a cool, dry place at a temperature of between 68 to 77 degrees Fahrenheit.[3]

Toxicity

Loratadine cardiotoxicity such as cardiac arrhythmias and prolongation of QT-interval are possible in patients, especially in the elderly, if taken at a higher than the recommended dose in 24 hours. Though rare, overdosing on loratadine may cause significant toxicity, including agitation and symptoms of the anticholinergic syndrome. Symptoms include, but are not limited to; mydriasis, urinary retention, tachycardia, and skin flushing.[11][12][13] 

Treatment protocol for loratadine toxicity may involve providing supplemental oxygen and cardiac monitoring. Sodium bicarbonate may be given to treat arrhythmias and prolonged QT-intervals in patients with suspected toxicity. Alleviation of agitation can be with benzodiazepines due to their high therapeutic index. Adults with symptoms of anticholinergic poisoning due to loratadine toxicity may receive physostigmine antidote therapy (recommended dose is between 0.5 to 2 mg IV). The recommendation is that only a medical toxicologist should supervise antidote therapy.

Enhancing Healthcare Team Outcomes

Loratadine is proven to be an effective and safe medication for alleviating symptoms of allergic rhinitis and treating urticaria. The drug is available as an over-the-counter medication; thus, it is essential to have a pharmacist educate the patient on the therapeutic dose of the medicine. The primary care physician and/or the nurse practitioner must counsel the patient on the importance of reading labels to avoid taking more than the recommended dose to prevent any drug-related toxicities. While loratadine is a relatively safe drug, healthcare providers should inform patients of all the side effects associated with the medication. Healthcare providers should also check liver and kidney function prior to prescribing the medication in individuals with hepatic and renal impairments. All members of the interprofessional team, as cited above, need to practice collaborative communication to ensure the best possible patient outcomes for loratadine therapy. [Level V]


References

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