Quantification of Niacin and Its Metabolite Nicotinuric Acid in Human Plasma by LC-MS/MS: Application to a Clinical Trial of a Fixed Dose Combination Tablet of Niacin Extended-Release/Simvastatin (500 mg/10 mg) in Healthy Chinese Volunteers

Table 2

Stability data for stock solutions of NA and NUA 6 h in room temperature and 7 days at −20°C (before and after).

	Response (×10^5)
	Before	Six h at room temperature	Seven days at −20°C
NA	14.7	14.6	13.9
	15.5	15.6	15.4
	14.2	14.1	13.9
	14.0	15.8	14.2
	14.7	15.1	14.3
	16.9	13.8	13.1
R.E.%		−1.1	−5.8
NUA	6.0	6.8	6.1
	6.6	6.5	6.3
	6.3	6.5	6.4
	6.4	6.7	6.4
	6.5	6.3	6.6
	7.0	6.3	6.5
R.E.%		0.8	−1.6