Radioimmunoassay of Flunisolide in Human Plasma

Flunisolide is a fast-acting corticoid designed for the treatment of allergic rhinitis, asthma, and other allied respiratory disorders in humans. As the quantum of drug delivered by inhalation (/. e., the usual route of administration of the drug), is invariably small, the plasma-levels attained can also be fairly small. Hence, there is a dire need for a sensitive method of plasma concentration evaluation which is satisfied by radioimmunoassay. 

An emulsion of the hapten (i.e., conjugate) in normal saline is prepared by mixing with an equal volume of Freund s complete adjuvant. The prepared emulsion is injected subcutaneously into four different sites in New Zealand albino rabbits. Six weeks after the initial injection, all the animals are placed on a regimen of weekly booster shots. After a period of six months, antiserum from these animals are harvested and dilutions of 1 10,000 to 1 30,000 produced 50% binding or more and is employed in the RIA. 

RIA-Procedure The following steps are to be adopted in a sequential manner, namely  

The percentage inhibition is calculated and the values obtained from the first set of tubes is used to plot a standard curve. The concentrations of flunisolide from the standard curve values from their calulated percentage inhibition value as depicted in figure 32.5 below  

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