Question

Although knowing exactly how much Aspirin is in a tablet is good indicator of
how much dose was given to a person, it does not however, give the exact
quantity absorbed into the bloodstream. Describe what experiment you would
perform to try and decipher the quantity of Aspirin absorbed.

Answer 1

There are many ways available in pharmacology, to estimate the exact quantity of drug in blood stream.

I am giving one the the technique on which I have worked. Of course we had chosen this method from literature which is available.

Determination of aspirin and salicylic acid in human plasma by column-switching liquid chromatography using on-line solid-phase extraction.

A column-switching liquid chromatographic method is described for the simultaneous determination of aspirin and salicylic acid in human plasma.

Blood samples are taken into chilled tubes containing a fluoride anticoagulant, and the plasma is isolated by centrifugation. Following a simple acidification step, a 200 microL aliquot of the sample is injected directly onto the HPLC system.

The C-18 extraction column is washed with acidified water for 2 min, after which time the compounds are removed by back-flushing directly onto the analytical column (C-8 Nucleosil, 5 microns, 250 mm x 4.6 mm).

The flow rate through both columns is 1 mL/min, and the analytes are quantified by measurement of their UV absorbance at 225 nm. The mobile phase is a mixture of water-methanol-acetonitrile-orthophosphoric acid (650:200:150:1 v/v/v/v).

The method is linear in the concentration ranges 0.10-5.00 micrograms/mL for aspirin and 0.25-15.00 micrograms/mL for salicylic acid. Both compounds have a limit of quantitation of 0.10 microgram/mL and a limit of detection of 0.04 microgram/mL.

Extensive stability tests have been carried out, and validation studies reveal the method to be reproducible and repeatable.

Excellent recoveries from plasma obviate the need for an internal standard. The procedure is easier to execute and requires less sample handling than methods currently described in the literature.

It has been successfully applied to the investigation of the levels of aspirin and salicylic acid in a healthy, nonfasting volunteer following a 600 mg oral dose of aspirin.