Loratadine

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Loratadine

Loratadine is a drug used to treat allergies. It is marketed by Schering-Plough under several trade names such as Claritin®, Clarityn® or Claratyne® depending on the market, by Lek as Lomilan and by Wyeth as Alavert. It is also available as a generic. Its active metabolite, desloratadine, is also on the market, though loratadine itself is the only drug of its class available over the counter (at least in the U.S. and UK as of 2005; desloratadine is available off the shelf in Canada). Claritin-D 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.

Available forms

Loratadine is available as tablets and oral suspension, and also in combination with pseudoephedrine. Also available are quick-dissolving tablets, which are advertised as being faster to get into one's system but which require special handling to avoid degrading in the package.

Mechanism of action

Loratadine is a tricyclic antihistamine, which has a selective and peripheral H₁-antagonist action. It has a long-lasting effect and does not normally cause drowsiness because it does not readily enter the central nervous system.

Pharmacokinetics

Loratadine is rapidly absorbed from the gastro-intestinal 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. The half-life of loratadine is on average 8 hours, and its metabolites 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

Most common side-effects are fatigue, drowsiness, dry mouth, headache and gastrointestinal disturbances.

Loratadine vs. desloratadine

This issue is covered in more depth in the article on desloratadine. Similar opinions to that below have been issued by a number of independent bodies internationally. A November 2003 article published in the journal American Family Physician about the safety, tolerability, effectiveness, price, and simplicity of desloratadine concluded the following:

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.

External links and references

Desloratadine for Allergic Rhinitis, a November 2003 article from American Family Physician
What are the differences between Claritin and Claritin-D, and Allegra and Allegra-D?