Laropiprant 20 mg, Niacin 1000 mg (ER) Tablets

The mechanism by which niacin alters lipid profiles has not been well defined. It may involve several actions including partial inhibition of release of free fatty acids from adipose tissue, and increased lipoprotein lipase activity, which may increase the rate of chylomicron triglyceride removal from plasma. Niacin decreases the rate of hepatic synthesis of VLDL and LDL, and does not appear to affect fecal excretion of fats, sterols, or bile acids.

Absorption — Due to extensive and saturable first-pass metabolism, niacin concentrations in the general circulation are dose dependent and highly variable. Time to reach the maximum niacin plasma concentrations was about 5 hours following niacin extended-release tablets. To reduce the risk of gastrointestinal (GI) upset, administration of niacin extended-release tablets with a low-fat meal or snack is recommended.

Single-dose bioavailability studies have demonstrated that the 500 mg and 1000 mg tablet strengths are dosage form equivalent but the 500 mg and 750 mg tablet strengths are not dosage form equivalent.

Metabolism — The pharmacokinetic profile of niacin is complicated due to extensive first-pass metabolism that is dose-rate specific and, at the doses used to treat dyslipidemia, saturable. In humans, one pathway is through a simple conjugation step with glycine to form nicotinuric acid (NUA). NUA is then excreted in the urine, although there may be a small amount of reversible metabolism back to niacin. The other pathway results in the formation of nicotinamide adenine dinucleotide (NAD). It is unclear whether nicotinamide is formed as a precursor to, or following the synthesis of, NAD. Nicotinamide is further metabolized to at least N-methylnicotinamide (MNA) and nicotinamide-N-oxide (NNO). MNA is further metabolized to two other compounds, N-methyl-2-pyridone-5-carboxamide (2PY) and N-methyl-4-pyridone-5-carboxamide (4PY). The formation of 2PY appears to predominate over 4PY in humans. At the doses used to treat hyperlipidemia, these metabolic pathways are saturable, which explains the nonlinear relationship between niacin dose and plasma concentrations following multiple-dose niacin extended-release tablets administration.

Nicotinamide does not have hypolipidemic activity; the activity of the other metabolites is unknown.

Elimination — Following single and multiple doses, approximately 60 to 76% of the niacin dose administered as niacin extended-release tablets was recovered in urine as niacin and metabolites; up to 12% was recovered as unchanged niacin after multiple dosing. The ratio of metabolites recovered in the urine was dependent on the dose administered.

Pediatric Use — No pharmacokinetic studies have been performed in this population (£16 years) [see Use in Specific Populations (8.4)].

Geriatric Use — No pharmacokinetic studies have been performed in this population (>65 years) [see Use in Specific Populations (8.5)].

Renal Impairment — No pharmacokinetic studies have been performed in this population. Niacin extended-release tablets should be used with caution in patients with renal disease [see Warnings and Precautions (5)].

Hepatic Impairment — No pharmacokinetic studies have been performed in this population. Active liver disease, unexplained transaminase elevations and significant or unexplained hepatic dysfunction are contraindications to the use of niacin extended-release tablets [see Contraindications (4) and Warnings and Precautions (5.3)].

Gender — Steady-state plasma concentrations of niacin and metabolites after administration of niacin extended-release tablets are generally higher in women than in men, with the magnitude of the difference varying with dose and metabolite. This gender differences observed in plasma levels of niacin and its metabolites may be due to gender-specific differences in metabolic rate or volume of distribution. Recovery of niacin and metabolites in urine, however, is generally similar for men and women, indicating that absorption is similar for both genders [see Gender (8.8)].

Fluvastatin — Niacin did not affect fluvastatin pharmacokinetics [see Drug Interactions (7.1)].

Lovastatin — When niacin extended-release tablets 2000 mg and lovastatin 40 mg were co-administered, niacin extended-release tablets increased lovastatin Cmax and AUC by 2% and 14%, respectively, and decreased lovastatin acid Cmax and AUC by 22% and 2%, respectively. Lovastatin reduced niacin extended-release tablets bioavailability by 2-3% [see Drug Interactions (7.1)].

Simvastatin — When niacin extended-release tablets 2000 mg and simvastatin 40 mg were co-administered, niacin extended-release tablets increased simvastatin Cmax and AUC by 1% and 9%, respectively, and simvastatin acid Cmax and AUC by 2% and 18%, respectively. Simvastatin reduced niacin extended-release tablets bioavailability by 2% [see Drug Interactions (7.1)].