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 3

Stability data for NA and NUA in human plasma under different storage conditions (before and after analysis, ).

	Storage conditions	Added	Before /R.E.	Found /R.E.
		(ng/mL)	(ng/mL)/%	(ng/mL)/%
NA	Short-term; (3 h at 24°C)	10.0	9.4/−5.8	9.1/−8.9
		60.0	60.2/0.4	58.8/−2.1
		600.0	611.0/2.17	636.3/6.0
	Long-term; (2 months at −20°C)	10.0	9.4/−5.7	9.6/−4.1
		60.0	56.0/−6.6	53.7/−10.6
		600.0	527.0/−12.2	595.3/−0.8
	Three freeze/thaw cycles	10.0	9.4/−1.9	9.5/−4.6
		60.0	60.2/0.4	58.0/−3.28
		600.0	611.0/1.8	546.3/−9.0
	Autosampler for 4 h (24°C)	10.0	9.9/−1.0	9.6/−3.7
		60.0	61.6/2.6	62.7/4.5
		600.0	597.4/0.4	578.3/−3.6
NUA	Short-term; (3 h at 24°C)	10.0	10.8/7.7	11.0/9.7
		60.0	60.1/0.2	63.6/5.9
		600.0	624.7/4.1	628.7/4.8
	Long-term; (2 months at −20°C)	10.0	10.2/2.3	10.6/6.4
		60.0	60.5/0.8	59.1/−1.5
		600.0	608.0/1.3	579.3/−3.4
	Three freeze/thaw cycles	10.0	10.8/7.7	10.8/8.3
		60.0	60.1/0.2	63.3/5.6
		600.0	624.7/4.1	618.3/3.1
	Autosampler for 4 h (24°C)	10.0	10.9/9.3	10.7/7.3
		60.0	59.4/−0.9	67.0/11.7
		600.0	611.3/1.9	598.3/−0.3