STUDY OF THE CLOUD POINT OF NORTRIPTYLINE HYDROCHLORIDE: EFFECT OF ADDITIVES

The work focuses on the clouding and dye solubilization phenomena in an amphiphilic drug, nortriptyline hydrochloride (NOT), which is a tricyclic antidepressant. A 30 mM drug solution prepared in 10 mM sodium phosphate buffer (pH: 7.07) showed CP at 45°C, which was found to decrease with the addition of long-chain alcohols and cyclohexanol but remained almost constant with short-chain alcohols. The behavior is explained on the basis of their nature: short-chain alcohols are water soluble and partition very little in micelles, whereas long-chain alcohols are hydrophobic and solubilize in drug aggregates. Diols decreased the CP. Addition of cationic surfactants increased the CP, whereas sugars caused a decrease. Dye solubilization results indicate micellar growth with fixed concentrations of surfactants.