Determination of ionization constants of some drugs used in the treatment of allergic rhinits by liquid chromatography

Allergies and diseases are the most common problems these days. Allergic rhinitis is also a type of allergy and is characterized by different and overreaction of the immune system against normally harmless substances. In children; attention deficit, exam failure, lack of concentration and self-confidence may lead to a decrease. In adults, depression, anxiety, and decrease in work productivity may result in a decrease in quality of life. In the treatment of allergic rhinitis, primarily allergens and drug treatment are used. Antihistamines are used to reduce the effect of allergens. Therefore, physicochemical parameters, side effects and drug interactions such as solubility, biological activity, absorption, lipophilic effects and ionization constants of these drugs have been investigated in recent years. The ionization constant (pK a ) is the pH at which the ionized and non-ionized forms of a molecule are equal to each other. pK a value affects the drug absorption. Because most of the drugs are insoluble in water, water-organic solvent binary mixtures are used in the determination of ionization constants. In this thesis, ionisation constant values ​​of loratadine and desloratadine in water-acetonitrile solvent mixture of antihistaminic drugs were determined by HPLC method. The pK a values ​​obtained by using nonlinear regression program (NLREG) were changed to pK a values ​​in water by means of Mole fraction-pK a method and Yasuda-Shedlovsky extrapolation method. It was observed that the data obtained were in harmony with the data calculated by the computer program. Keywords: Ionization constant, Liquid Chromatography Method, Allergic Rhinitis