Loratadine
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| Routes of administration | oral |
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| Pharmacokinetic data | |
| Bioavailability | N/A due to extensive first-pass metabolism |
| Metabolism | hepatic |
| Elimination half-life | 8 hours (metabolites 12-24 hours) |
| Excretion | 40% as conjugated metabolites into urine similar amount into the feces |
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| ECHA InfoCard | 100.120.122 |
| Chemical and physical data | |
| Formula | C22H23ClN2O2 |
| Molar mass | 382.88 g/mol g·mol−1 |
Loratadine is a drug used to treat allergies. It is marketed by Schering-Plough under several trade names such as Claritin, Claritine, Clarityn or Clarityne depending on the market, by Lek as Lomilan, by Ranbaxy as Roletra and by Wyeth as Alavert. It is also available as a generic. In the U.S. and UK, loratadine is the only drug of its class available over the counter.
In the UK, larger quantities are only available over the counter (they are "P-Line" and can only be sold in the presence of a pharmacist), whereas packets of up to and including 7 tablets are available "off the shelf" (GSL).
Its active metabolite, desloratadine, is also on the market, though can only be purchased over-the-counter in Canada.
In Claritin-D (also marketed as Clarinase), loratadine is combined with pseudoephedrine, a decongestant; this makes it somewhat useful for colds as well as allergies, but adds a potential side-effect of insomnia, nervousness and anxiety.
Available forms
Loratadine is available as tablets, oral suspension and syrup, and also in combination with pseudoephedrine.
Also available are quick-dissolving tablets, which are marketed as being faster to get into one's circulatory system but which require special handling to avoid degrading in the package.
Indications
Loratadine is indicated for the symptomatic relief of allergy such as hay fever (allergic rhinitis), urticaria (hives).
For allergic rhinitis (hay fever), loratadine is effective for both nasal and eye symptoms: sneezing, runny nose, itchy or burning eyes.
Dose
Treatment by mouth (oral)
- ADULT and CHILD over 6 years: 10 mg daily
- CHILD 2-5 years: 5 mg daily
Mechanism of action
Loratadine is a tricyclic antihistamine, which selectively antagonizes peripheral histamine H1-receptors. Histamine is responsible for many features of allergic reactions.
Loratadine has a long-lasting effect and does not normally cause drowsiness because it does not readily enter the central nervous system (see Side-effects section below).
Pharmacokinetics
Loratidine is given orally, are well absorbed from the gastrointestinal tract and it has rapid first-pass hepatic metabolism. Loratadine is almost totally bound to plasma proteins. Its metabolite, desloratadine (descarboethoxyloratadine), is also active, but binds to plasma proteins only moderately.
Loratadine's peak effect occurs in 1-2 hours, and its biological half-life of loratadine is on average 8 hours with its metabolites half-life being 28 hours. About 40% is excreted as conjugated metabolites into the urine and similar amount into the feces. Traces of unmetabolised loratadine can be found in the urine.
Side-effects
Non-sedating antihistamine
As a non-sedating antihistamine, loratadine causes less sedation and psychomotor impairment than the older antihistamines because it penetrates the blood brain barrier only to a slight extent. Any drowsiness, which is unlikely, may diminish after a few days of treatment.
Although drowsiness is rare, nevertheless patients should be advised that it can occur and may affect performance of skilled tasks (e.g. driving); excess alcohol should be avoided.
Most common side-effects
Drowsiness, headache, psychomotor impairment, and antimuscarinic effects such as urinary retention, dry mouth, blurred vision, and gastrointestinal disturbances.
Other rarer side-effects
Hypotension, extrapyramidal effects, dizziness, confusion, depression, sleep disturbances, tremor, convulsions, palpitation, arrhythmias, hypersensitivity reactions (including bronchospasm, angioedema, and anaphylaxis, rashes, and photosensitivity reactions), blood disorders, liver dysfunction, and angle-closure glaucoma.
Cautions and contraindications
Loratadine should be used with caution in hepatic disease and dose reduction may be necessary in renal impairment. Caution may be required in epilepsy. Children and the elderly are more susceptible to side-effects (see Side-effects section above). Also contraindicated (avoid) in pregnancy and breast-feeding.
Clinical trials and efficacy
Loratadine vs. desloratadine
A November 2003 article published in the journal American Family Physician about the safety, tolerability, effectiveness, price, and simplicity of desloratadine concluded the following:[2]
- "Desloratadine is similar in effectiveness to fexofenadine and would be expected to produce results similar to loratadine and other nonsedating antihistamines. There is no clinical advantage to switching a patient from loratadine to desloratadine. However, it may be an option for patients whose medical insurance no longer covers loratadine if the co-pay is less than the cost of the over-the-counter product."
References
- ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 Oct 2023.
- ^ See S (2003). "Desloratadine for allergic rhinitis". Am Fam Physician. 68 (10): 2015–6. PMID 14655812.
External links
- Loratadine — MedlinePlus Drug Information, U.S. National Library of Medicine, National Institutes of Health
- Claritin (loratadine) drug description — RxList (Internet Drug Index)
- Claritin — patient information leaflet
- DrugBank: Loratadine — Wishart DS et al., DrugBank: a comprehensive resource for in silico drug discovery and exploration. Nucleic Acids Res. 2006 1;34