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A radioimmunoassay for metoclopramide
M De Villiers1, D Parkin, P Van Jaarsveld
1Department of Pharmacology, University of Stellenbosch Medical School, Tygerberg, Republic of South Africa.
Journal of Immunological Methods
|October 23, 1987
Summary
A new radioimmunoassay accurately measures the anti-emetic drug metoclopramide at low levels. This method utilizes photolytic coupling and radioiodination for precise quantification.
Area of Science:
- Analytical Chemistry
- Pharmacology
- Immunology
Background:
- Metoclopramide is a widely used anti-emetic drug.
- Accurate quantification of metoclopramide is essential for therapeutic drug monitoring and pharmacokinetic studies.
- Existing methods may lack the sensitivity required for detecting low concentrations.
Purpose of the Study:
- To develop a sensitive radioimmunoassay (RIA) for quantifying metoclopramide.
- To characterize the antibody-antigen interaction and assess assay specificity.
Main Methods:
- Development of a metoclopramide-bovine serum albumin conjugate using photolytic coupling.
- Preparation of a radioiodinated (125I) metoclopramide derivative.
- Characterization of antibody binding using Scatchard analysis.
- Assessment of cross-reactivity with structurally related compounds like lignocaine.
Main Results:
- A highly sensitive RIA capable of detecting metoclopramide in the picomole (pmol) range was successfully developed.
- The antibody exhibited a high affinity for metoclopramide, with a dissociation constant (Kd) of 3 x 10(-11) mol/L.
- The assay demonstrated negligible cross-reactivity with lignocaine, indicating good specificity.
Conclusions:
- The developed radioimmunoassay provides a sensitive and specific method for metoclopramide quantification.
- This assay is suitable for pharmacokinetic studies and therapeutic drug monitoring of metoclopramide.
- The methodology establishes a robust platform for developing RIAs for other small molecules.