Stability of oleander extract and oleandrin in sera stored in plastic serum separator tubes

Oleander poisoning is common in the southern parts of the United States as well as part of Europe and South East Asia. The fluorescence polarization immunoassay (FPIA) for digoxin cross-reacts with oleandrin, the major poison of oleander extract and can be used for rapid detection of oleander poisoning. However, for medicolegal investigation, the presence of oleandrin should be confirmed by a more sophisticated analytical technique such as liquid chromatography combined with tandem mass spectrometry. We studied stability of oleander extract as well as oleandrin in serum samples stored in Becton Dickinson plastic serum separator tubes (SSTs) by comparing values obtained in parallel specimens stored in plain glass tubes and in red-topped plastic tubes.

Oleander leaves were extracted using absolute ethanol, and drug-free serum pools were supplemented with oleander extract or ethanolic solution of pure oleandrin. Aliquots of the supplemented pools were then stored in plain glass tubes, red-topped plastic tubes or SSTs and the stability of oleander extract or oleandrin in sera were studied by the FPIA digoxin assay for varying times up to seven days.

We observed no statistically significant change in apparent digoxin concentrations in specimens stored in SSTs even after seven days of storage compared to original values observed in the supplemented serum pools.

Specimens can be stored in SSTs for up to seven days prior to analysis of oleandrin concentration.