Question

Loratadine (proprietary name Claritin) is an antihistamine drug used to treat allergies, and marketed for its non-sedating properties. Loratadine is a tricyclic antihistamine, which selectively antagonizes peripheral histamine H₁-receptors, which are G-protein coupled receptors. It is given orally and is well absorbed from the gastrointestinal tract. Loratadine has rapid and extensive first-pass hepatic metabolism; it is metabolized by isoenzymes of the cytochrome P450 system, including CYP3A4 and CYP2D6. Loratadine is almost totally bound to plasma proteins. Its metabolite, desloratadine (descarboethoxyloratadine), is also active, but binds to plasma proteins to a much lesser extent. Select the true statement(s):

a. until it’s eliminated, desloratadine will potentiate the effects of loratadine

b. loratadine will inhibit CYP3A4 in the presence of desloratadine

c. loratadine’s binding to the plasma proteins will induce CYP2D6

d. loratidine and desloratidine are expected to have similar Volumes of Distribution

e. loratidine and desloratidine are expected to have similar elimination half-lives

Please answer it with explanation

Answer 1

Loratidine attainsits biological peak at 1-2 hour and half life average 8 hour (3-20 hour)

Desloratidine Which is active metabolite of loratidine has half life of 27 (9-97 hour).

Loratidine is bount to plasma protein (~97%) more efficiently than desloratidine.

Desloratidine more respoy for antihistaminic effect.

They are metablolised by the isoenzymes of Cytochrome450.that are CYP3A4 and CYP2D6.

The CYP3A4 Inhibitors will increase the plasma concentration of loratidine.

So the correct option is-

Loratidine binding to plasma protein will induce CYP2D6 Enzyme..

Thank you..