Development of HPLC method for quantification of valsartan in rabbit plasma
A simple,specific and sensitive HPLC method was developed and validated for the determination of valsartan in rabbit plasma. Separation was carried out on a reverse-phase C18 column (250mm×4.6mm i.d., 5µm particle size), using a mixture of acetonitrile and 10mM phosphate buffer (pH 3.0) in the ratio of 40:60 (% v/v) at a flow rate of 1.0 ml/min with UV detection at 250 nm within 20 min. Telmisartan was used as internal standard (IS). The concentration was quantified based on drug/IS peak area ratios. The plasma samples were prepared by a simple liquid extraction method with MTBE and methanol, which was evaporated under gentle stream of nitrogen. The residue was reconstituted in mobile phase and aliquots were injected to HPLC system, yielding more than 96% extraction efficiencies. The retention time was found to be 10.8 ± 0.3 and 16.9 ± 0.2 min for drug and IS respectively. The calibration curve was linear (correlation coefficient of 0.9983) in the concentration range of 50–7000 ng/ml. The limit of detection and limit of quantitation were found to be 18.22 ng/ml and 49.21 ng/ml respectively. Both the intra-day and inter-day precisions at three tested concentrations were below 1.0 % R.S.D. The extraction efficiency of Val from rabbit plasma samples was ranged from 96.07 to 98.1% (R.S.D. was less than 1.0) at all three concentration levels, which confirm no interference effects due to plasma components. Recovery of IS was found to be 96.53% (R.S.D. = 0.84). The processed samples are stable at room temperature for 3 days. All samples were found to be stable after 3 freeze thaw cycles.
The developed method was successfully applied for estimating the pharmacokinetic parameters of valsartan following oral administration of 7.5 mg tablet and programmable release capsules to rabbits. Absorption of valsartan after oral administration was rapid with the conventional tablet (Tmax 1 hr), but with timed release capsule, absorption was slow and showed Tmax value 6 hr. The developed method was found to be suitable for pharmacokinetic and bioavailability studies of valsartan in rabbit blood samples. The present method was found to be selective enough to analyze valsartan in rabbit plasma without any tedious extraction procedure.
Author profile page link: http://www.pharmainfo.net/vamsikrishna-reddy
Co-author profile page link: http://www.pharmainfo.net/usha-yogendra-nayak
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