A new inclusion complex of amlodipine besylate and soluble β-cyclodextrin polymer: preparation, characterization and dissolution profile

Abstract

Amlodipine besylate (AML) has become the most popular blood pressure medication for hypertensive pets. It belongs to the class I (high solubility and high permeability) according to BCS and is marketed in Europe only as white tablets equivalent to 2.5, 5.0 and 10.0 mg of amlodipine for oral administration. Unfortunately, oral AML dosage for cats and dogs is in the range 0.1–0.2 and 0.625–0.125 mg/kg/die respectively. Moreover, AML shows a slight solubility in water according to Ph. Eur. 7°. According to these considerations, the aim of this work was the complexation between soluble β-cyclodextrin polymer (CD) and AML using the solubilization/freeze-dried method to obtain powders easily dosable and soluble in water for the treatment of hypertension in pets. The complex in solution was evaluated by phase solubility studies that indicated the optimal 2:1 drug/CD ratio to form a stable complex. UV–Vis absorption and circular dichroism showed the formation of a complex with a weak bond such as confirmed by differential scanning calorimetry, infrared spectroscopy and fluorescence microscopy. In vitro dissolution/release tests were performed in water to investigate the influence of formulative parameters on drug dissolution/release properties. The inclusion of AML in CD increased its wettability, dissolution rate and solubility in water. This method could be a suitable approach for the administration of an extemporaneous solution of the antihypertensive drug to guarantee a correct dose to pets increasing the compliance.