Table 4.

Stability of the derivatized clopidogrel active metabolite (CAM-D) at 20 ng/mL, clopidogrel at 15.3 ng/mL, and clopidogrel carboxylic acid at 500 ng/mL was evaluated after three freeze-thaw cycles (−80°C/room temperature) in citrate-treated plasma. Data are presented as percent deviation from the nominal concentration. Values are the average of duplicate determinations, which varied by less than 15% from the nominal concentration. The largest decrease was 13% of both clopidogrel and clopidogrel carboxylic acid and 8% decrease of CAM-D.

	Deviation from nominal concentration (%)
	CAM-D	Clopidogrel	Clopidogrel carboxylic acid
1 Freeze Thaw Cycle	−7	1	−7
2 Freeze Thaw Cycles	1	15	−7
3 Freeze Thaw Cycles	−8	−13	−13