Determination of sustained-release niacin formulation by RP-HPLC in dog plasma and its pharmacokinet

AIM: To establish a simple RP-HPLC method for the determination of niacin in dog plasma and calculate the relative bioavailability and the pharmacokinetic parameters of sustained-release niacin formulation. METHODS: Niacin was extracted from dog plasma with perchloric acid. The RP-HPLC was performed on a Lichrospher C_ 18 column (5 μm, 250 mm× 4.6 mm I.D.) with mobile phase of acetonitrile -10 mmol·L -1 monopotassium phosphate (892, v/v), and the pH of the water phase was adjusted to 4.0 with phosphoric acid at flow rate of 1.0 ml·min -1. Niacin was detected by UV absorbance at 263 nm. Single dose of sustained-release niacin formulation (500 mg) and rapid-release niacin formulation (500 mg) were given to six Beagle dogs. RESULTS: The t_ 1/2, T_ max, C_ max and MRT of niacin in the sustained release formulation were 1.25± 1.15 h, 2.3± 0.8 h, 35.3± 4.87 mg·L -1 and 3.45± 0.55 h, respectively. The T_ max of sustained-release niacin formulation is significantly longer than that of the conventional niacin tablet (P< 0.05), the C_ max was significantly lower than that of the conventional niacin tablet (P< 0.05). CONCLUSION: This method is simple, accurate, sensitive and applicable for pharmacokinetic study of niacin. The relative bioavailability is ( 40.7± 8.6)% in the sustained-release formulation.