Serum, plasma, or whole blood
Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant
Separate serum or plasma within one hour of collection and transfer to a plastic transport tube.
Stable for 14 days refrigerated. Stable at room temperature or frozen for 14 days