Question

A 14-year-old girl suffering from seasonal rhinitis started a therapy with Loratadine (Claritin), a drug that binds to H₁ histamine receptors. How would you describe the relationship between Loratidine (Claritin) and the histamine receptor? (select all that apply)

            a. Loratidine (Claritin)  is an agonist for the H₁ receptor

            b. Loratidine (Claritin)  is an antagonist for the H₁ receptor

            c. The H₁ receptor binds to Loratidine (Claritin)

            d. Loratidine (Claritin)  is a partial agonist for the H₁ receptor

            e. Histamine is an agonist for the H₁ receptor     

            f. Histamine is an antagonist for the H₁ receptor

            e. Histamine displays efficacy on a dose response curve

Answer 1

Options b and e.

a. Loratadine (Claritin) is an agonist for H1 receptor: Incorrect

b. Loratadine (Claritin) is an antagonist for H1 receptor: Correct

c. The H1 receptor binds to Loratadine: Incorrect – Loratadine interferes with the agonist activity of histamine at the H1 receptor thereby relieving allergic symptoms.

d. Loratadine is a partial agonist for the H1 receptor: Incorrect

e. Histamine is an agonist for the H1 receptor: Correct

f. Histamine is an antagonist for the H1 receptor: Incorrect

g. Histamine displays efficacy on a dose response curve: Incorrect – Loratadine displays the curve.