Loratadine is a piperidine histamine H1-receptor antagonist with anti-allergic properties and without sedative effects. Loratadine blocks the H1 histamine receptors and prevents the symptoms that are caused by histamine activity on capillaries, bronchial smooth muscle, and gastrointestinal smooth muscle, including vasodilatation, increased capillary permeability, bronchoconstriction, and spasmodic contraction of gastrointestinal smooth muscle. Loratadine does not cross the blood-brain barrier and does not cause central nervous system effects.
Loratadine is a derivative of azatadine and a second-generation histamine H1 receptor antagonist used in the treatment of allergic rhinitis and urticaria. Unlike most classical antihistamines (histamine H1 antagonists) it lacks central nervous system depressing effects such as drowsiness.
Mechanism of Action of Loratadine
Loratadine competes with free histamine and exhibits specific, selective peripheral H1antagonistic activity. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms (eg. nasal congestion, watery eyes) brought on by histamine. Loratadine has low affinity for cholinergic receptors and does not exhibit any appreciable alpha-adrenergic blocking activity in-vitro. Loratadine also appears to suppress the release of histamine and leukotrienes from animal mast cells, and the release of leukotrienes from human lung fragments, although the clinical importance of this is unknown. Loratadine is a long acting second generation antihistamine that is similar in structure to cyproheptadine and azatadine. The pharmacology of loratadine is similar to other antihistamines, but unlike other H1-blockers, loratidine is shown to exhibit competitive, specific, and selective antagonism of H1 receptors. The exact mechanism of this interaction is unknown, but the disposition of the drug suggests that loratadine’s prolonged antagonism of histamine may be due to the drug’s slow dissociation from the receptor or the formation of the active metabolite, desloratadine. Loratadine does not penetrate the CNS effectively and has a low affinity for CNS H1-receptors.
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During hypersensitivity reactions, histamine is one of many potent autacoids released, and its relative contribution to the ensuing symptoms varies widely with species and tissue. The protection afforded by histamine antagonists obviously varies accordingly. In human beings, some phenomena, including edema formation and itch, are fairly well controlled; others, such as hypotension, are less so. Broncoconstriction is reduced little, if at all.
Indications of Loratadine
- Pruritus
- Seasonal Allergic Rhinitis
- Allergic Rhinitis
- Allergic Reactions
- Urticaria
- Allergic intraocular inflammatory diseases
- Atopic eczema
- Inflammatory dermatoses
- Nasal and eye symptoms, sneezing, runny nose,
- Itchy or burning eyes.
- Skin allergies.
- Runny nose, itchy, watery eyes, sneezing, itching of the nose/throat)
- Self-Medication that is used alone or in combination with pseudoephedrine sulfate for the symptomatic relief of seasonal allergic rhinitis. Also used for the symptomatic relief of pruritus, erythema, and urticaria associated with chronic idiopathic urticaria in patients (not for children under 6 unless directed by a clinician).
Contra-Indications of Loratadine
Patients with severe hepatic (liver) disorders may need to start with a lower dose. No dose adaptation is necessary for elderly or really (kidney) impaired patients.
Loratadine is usually compatible with breastfeeding (classified category L-2 by the American Academy of Pediatrics). In the U.S., it is classified as category B in pregnancy, meaning animal reproduction studies have failed to demonstrate a risk to the fetus but no adequate and well-controlled studies in pregnant women have been conducted
Dosages of Loratadine
Strengths
- Tablets: 10 mg.
- Tablets, disintegrating: 5 and 10 mg.
- Tablets, chewable: 5 mg.
- Syrup: 5 mg/5 ml.
Allergic Rhinitis
- 10 mg orally once a day
- Maximum dose: 10 mg/day
Urticaria
- 10 mg orally once a day
- Maximum dose: 10 mg/day
Pediatric Dose
Allergic Rhinitis
- 2 to 5 years: 5 mg orally once a day
- Maximum dose: 5 mg/day
- 6 years and older: 10 mg orally once a day
- Maximum dose: 10 mg/day
Urticaria
- 2 to 5 years: 5 mg orally once a day
- Maximum dose: 5 mg/day
- 6 years and older: 10 mg orally once a day
- Maximum dose: 10 mg/day
Side Effects of Loratadine
The most common
- headache,
- drowsiness,
- fatigue and
- dry mouth.
- Sleepiness
- Stomach pain
- Headache
- Diarrhea
- An opposite reaction in which you feel excited, jittery, or nervous, known as paradoxical CNS stimulation instead of drowsy or sleepy
More common
- headache
- fast, pounding, or uneven heartbeat;
- fever, flu symptoms;
- seizure (convulsions); or
- jaundice (yellowing of the skin or eyes).
- dry mouth, sore throat, cough;
- muscle pain;
- drowsiness, tired feeling;
- nausea,
- fever, flu symptoms;
- seizure (convulsions); or
- jaundice (yellowing of the skin or eyes).
Less common
- Dizziness
- dry mouth
- dysmenorrhea, such as, difficult or painful menstruation
- dyspepsia, such as, acid or sour stomach, belching, heartburn, indigestion, stomach discomfort, upset or pain,
- fatigue, such as unusual tiredness or weakness
- myalgias, such as joint pain, swollen joints, muscle aching or cramping, muscle pains or stiffness, difficulty in moving
- pharyngitis, such as body aches or pain, congestion, cough, dryness or soreness of throat, fever, hoarseness, runny nose, tender swollen glands in the neck, trouble in swallowing, voice changes.
- somnolence, such as, sleepiness or unusual drowsiness
- nausea
- liver damage or inflammation
- tightness in the chest or breathing tube
- passing out or fainting
- seizures
Drug Interactions of Loratadine
Loratadine may interact with following drugs, supplements & may change the efficacy of drugs
- amiodarone
- aripiprazole
- buprenorphine
- ipratropium
- methotrimeprazine
- paraldehyde
- tiotropium
- zolpidem
- Cordarone, Nexterone, or Pacerone (amiodarone)
- Prezista (darunavir)
- Sprycel (dasatinib)
Antihistamines should be discontinued about 48 hr prior to skin allergy tests, since these drugs may prevent or diminish otherwise positive reactions to dermal activity indicators.
Pregnancy & Lactation of Loratadine
FDA Pregnancy Category B
Pregnancy
The safety of using this medication during pregnancy has not been established. Women who are pregnant should not use this medication. If you become pregnant while taking this medication, contact your doctor immediately.
Lactation
The safety of loratadine has not been established for women who are breast-feeding. Women who are breast-feeding should not take loratadine.
Children
The safety and effectiveness of using this medication have not been established for children younger than 2 years of age. For children between the ages of 2 and 12, do not give this medication for longer than 14 days, unless recommended by a doctor.
References
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