Abstract

Background: Aliskiren hemifumarate and amlodipine besylate are two anti-hypertensive drugs. They are used together in pharmaeutical dosage froms to lower blood pressure and relieve anginal pain.

Method: Five simple, sensitive and rapid spectrophotometric methods were presented for the determination of aliskiren hemifumarate and amlodipine besylate in their combined dosage form. These methods were based on direct measurement of amlodipine besylate at 360 nm; due to lack of interference of aliskiren hemifumarate, over a concentration range of 5-35 µg mL^-1 with mean recovery percentage 100.41±0.65. Aliskiren hemifumarate was determined without prior separation by; first derivative values at 290 nm (A), ratio difference method using values at 249 nm and 286.4 nm with 35 µg mL^-1 of amlodipine besylate as a divisor (B), derivative ratio values at 290.6 nm utilizing 35 µg mL^-1 of amlodipine besylate as a divisor (C), ratio subtraction method using values at 280.4 nm (D), measuring absorbance at isosbestic point 270.1 nm (E).

Results: These methods were found linear for aliskiren hemifumarate over a concentration range of 30- 150 µg mL^-1. The suggested methods were validated according to ICH guidelines using laboratoryprepared mixtures. Statistical analysis of the results showed no significant difference between the proposed and the reported methods with respect to accuracy and precision.

Conclusion: The suggested methods were found to be simple, accurate and selective regarding the two cited drugs. This allows for their incorporation in the quality control analysis where time and economy are of great value.

Keywords: Aliskiren hemifumarate, amlodipine besylate, derivative spectrophotometry, ratio difference, isosbestic point, ratio subtraction.

Graphical Abstract