Absorption
Nateglinide is rapidly absorbed following oral administration of Starlix tablets prior to a meal, with mean peak drug concentration generally occurring in less than 1 hour. Nateglinide is rapidly and almost completely (≥ 90%) absorbed from an oral solution. Absolute oral bioavailability is estimated to be 72%. In type 2 diabetic patients given Starlix over the dose range 60 to 240 mg before three meals per day for one week, nateglinide showed linear pharmacokinetics for both AUC and C
max, and t
max was independent of dose.
Distribution
The steady-state volume of distribution of nateglinide based on intravenous data is estimated to be approximately 10 litres.
In vitro studies show that nateglinide is extensively bound (9799%) to serum proteins, mainly serum albumin and to a lesser extent alpha
1-acid glycoprotein. The extent of serum protein binding is independent of drug concentration over the test range of 0.110 μg Starlix/ml.
Biotransformation
Nateglinide is extensively metabolised. The main metabolites found in humans result from hydroxylation of the isopropyl side-chain, either on the methine carbon, or one of the methyl groups; activity of the main metabolites is about 56 and 3 times less potent than nateglinide, respectively. Minor metabolites identified were a diol, an isopropene and acyl glucuronide(s) of nateglinide; only the isopropene minor metabolite possesses activity, which is almost as potent as nateglinide. Data available from both
in vitro and
in vivo experiments indicate that nateglinide is predominantly metabolised by CYP2C9 with involvement of CYP3A4 to a smaller extent.
Elimination
Nateglinide and its metabolites are rapidly and completely eliminated. Most of the [14C] nateglinide is excreted in the urine (83%), with an additional 10% eliminated in the faeces. Approximately 75% of the administered [
14C] nateglinide is recovered in the urine within six hours post-dose. Approximately 616% of the administered dose was excreted in the urine as unchanged drug. Plasma concentrations decline rapidly and the elimination half-life of nateglinide typically averaged 1.5 hours in all studies of Starlix in volunteers and type 2 diabetic patients. Consistent with its short elimination half-life, there is no apparent accumulation of nateglinide upon multiple dosing with up to 240 mg three times daily.
Food effect
When given post-prandially, the extent of nateglinide absorption (AUC) remains unaffected. However, there is a delay in the rate of absorption characterised by a decrease in C
max and a delay in time to peak plasma concentration (t
max). It is recommended that Starlix be administered prior to meals. It is usually taken immediately (1 minute) before a meal but may be taken up to 30 minutes before meals.
Special populations
Elderly
Age did not influence the pharmacokinetic properties of nateglinide.
Hepatic impairment
The systemic availability and half-life of nateglinide in non-diabetic subjects with mild to moderate hepatic impairment did not differ to a clinically significant degree from those in healthy subjects.
Renal impairment
The systemic availability and half-life of nateglinide in diabetic patients with mild, moderate (creatinine clearance 3150 ml/min) and severe (creatinine clearance 1530 ml/min) renal impairment (not undergoing dialysis) did not differ to a clinically significant degree from those in healthy subjects. There is a 49% decrease in C
max of nateglinide in dialysis-dependent diabetic patients. The systemic availability and half-life in dialysis-dependent diabetic patients was comparable with healthy subjects. Although safety was not compromised in this population dose adjustment may be required in view of low C
max.
GenderNo clinically significant differences in nateglinide pharmacokinetics were observed between men and women.