Interaction of primaquine and chloroquine with ionic micelles as studied by 1H NMR and electronic absorption spectroscopy.

The characteristics of binding of primaquine (PQ) and chloroquine (CQ) to micelles of surfactants with different charge of headgroups were studied by 1H-NMR and optical absorption spectroscopy. Cetyltrimethylammonium chloride (CTAC) was used as a cationic surfactant, sodium dodecylsulfate (SDS) as an anionic surfactant and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate (HPS) as zwitterionic. The pK values and binding constants were estimated. Interaction with SDS significantly increases an apparent pK of PQ and CQ. However, chemical shift patterns and values of binding constants in the presence of different surfactants show that mode of interaction of charged drugs with micelles is nonspecific, since the complexes formed are similar for different types of surfactants. Electrostatic forces alter the affinity between drugs and micelles bearing charged groups. Interaction of drugs with cationic micelles is prevented if the drug has two positive charges. HPS interacts with charged drugs in the same manner as CTAC rather than SDS.