"What are oral diabetes medications and how do they work?
Insulin is a hormone produced by cells in the pancreas called beta cells. Insulin helps the body use blood glucose (a type of sugar) for energy. People with type 2 diabetes "...
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Mechanism of Action
Nateglinide is an amino-acid derivative that lowers blood glucose levels by stimulating insulin secretion from the pancreas. This action is dependent upon functioning beta-cells in the pancreatic islets. Nateglinide interacts with the ATP-sensitive potassium (K+ATP) channel on pancreatic beta-cells. The subsequent depolarization of the beta cell opens the calcium channel, producing calcium influx and insulin secretion. The extent of insulin release is glucose dependent and diminishes at low glucose levels. Nateglinide is highly tissue selective with low affinity for heart and skeletal muscle.
Following oral administration immediately prior to a meal, nateglinide is rapidly absorbed with mean peak plasma drug concentrations (Cmax) generally occurring within 1 hour (Tmax) after dosing. When administered to patients with Type 2 diabetes over the dosage range 60 mg to 240 mg three times a day for one week, nateglinide demonstrated linear pharmacokinetics for both AUC (area under the time/plasma concentration curve) and Cmax. Tmax was also found to be independent of dose in this patient population. Absolute bioavailability is estimated to be approximately 73%. When given with or after meals, the extent of nateglinide absorption (AUC) remains unaffected. However, there is a delay in the rate of absorption characterized by a decrease in Cmax and a delay in time to peak plasma concentration (Tmax). Plasma profiles are characterized by multiple plasma concentration peaks when nateglinide is administered under fasting conditions. This effect is diminished when nateglinide is taken prior to a meal.
Based on data following intravenous (IV) administration of nateglinide, the steady-state volume of distribution of nateglinide is estimated to be approximately 10 liters in healthy subjects. Nateglinide is extensively bound (98%) to serum proteins, primarily serum albumin, and to a lesser extent α1 acid glycoprotein. The extent of serum protein binding is independent of drug concentration over the test range of 0.1-10 μg/mL.
Nateglinide is metabolized by the mixed-function oxidase system prior to elimination. The major routes of metabolism are hydroxylation followed by glucuronide conjugation. The major metabolites are less potent antidiabetic agents than nateglinide. The isoprene minor metabolite possesses potency similar to that of the parent compound nateglinide.
In vitro data demonstrate that nateglinide is predominantly metabolized by cytochrome P450 isoenzymes CYP2C9 (70%) and CYP3A4 (30%).
Nateglinide and its metabolites are rapidly and completely eliminated following oral administration. Within 6 hours after dosing, approximately 75% of the administered 14C-nateglinide was recovered in the urine. Eighty-three percent of the 14C-nateglinide was excreted in the urine with an additional 10% eliminated in the feces. Approximately 16% of the 14C-nateglinide was excreted in the urine as parent compound. In all studies of healthy volunteers and patients with Type 2 diabetes, nateglinide plasma concentrations declined rapidly with an average elimination half-life of approximately 1.5 hours. Consistent with this short elimination half-life, there was no apparent accumulation of nateglinide upon multiple dosing of up to 240 mg three times daily for 7 days.
In vitro drug metabolism studies indicate that Starlix is predominantly metabolized by the cytochrome P450 isozyme CYP2C9 (70%) and to a lesser extent CYP3A4 (30%). Starlix is a potential inhibitor of the CYP2C9 isoenzyme in vivo as indicated by its ability to inhibit the in vitro metabolism of tolbutamide. Inhibition of CYP3A4 metabolic reactions was not detected in in vitro experiments.
Glyburide: In a randomized, multiple-dose crossover study, patients with Type 2 diabetes were administered 120 mg Starlix three times a day before meals for 1 day in combination with glyburide 10 mg daily. There were no clinically relevant alterations in the pharmacokinetics of either agent.
Metformin: When Starlix 120 mg three times daily before meals was administered in combination with metformin 500 mg three times daily to patients with Type 2 diabetes, there were no clinically relevant changes in the pharmacokinetics of either agent.
Digoxin: When Starlix 120 mg before meals was administered in combination with a single 1-mg dose of digoxin to healthy volunteers, there were no clinically relevant changes in the pharmacokinetics of either agent.
Warfarin: When healthy subjects were administered Starlix 120 mg three times daily before meals for four days in combination with a single dose of warfarin 30 mg on day 2, there were no alterations in the pharmacokinetics of either agent. Prothrombin time was not affected.
Diclofenac: Administration of morning and lunch doses of Starlix 120 mg in combination with a single 75-mg dose of diclofenac in healthy volunteers resulted in no significant changes to the pharmacokinetics of either agent.
Geriatric: Age did not influence the pharmacokinetic properties of nateglinide. Therefore, no dose adjustments are necessary for elderly patients.
Gender: No clinically significant differences in nateglinide pharmacokinetics were observed between men and women. Therefore, no dose adjustment based on gender is necessary.
Race: Results of a population pharmacokinetic analysis including subjects of Caucasian, Black, and other ethnic origins suggest that race has little influence on the pharmacokinetics of nateglinide.
Renal Impairment: Compared to healthy matched subjects, patients with Type 2 diabetes and moderate-tosevere renal insufficiency (CrCl 15-50 mL/min) not on dialysis displayed similar apparent clearance, AUC, and Cmax. Patients with Type 2 diabetes and renal failure on dialysis exhibited reduced overall drug exposure. However, hemodialysis patients also experienced reductions in plasma protein binding compared to the matched healthy volunteers.
Hepatic Impairment: The peak and total exposure of nateglinide in non-diabetic subjects with mild hepatic insufficiency were increased by 30% compared to matched healthy subjects. Starlix® (nateglinide) should be used with caution in patients with chronic liver disease. (See PRECAUTIONS, Hepatic Impairment.)
Starlix is rapidly absorbed and stimulates pancreatic insulin secretion within 20 minutes of oral administration. When Starlix is dosed three times daily before meals there is a rapid rise in plasma insulin, with peak levels approximately 1 hour after dosing and a fall to baseline by 4 hours after dosing.
In a double-blind, controlled clinical trial in which Starlix was administered before each of three meals, plasma glucose levels were determined over a 12-hour, daytime period after 7 weeks of treatment. Starlix was administered 10 minutes before meals. The meals were based on standard diabetic weight maintenance menus with the total caloric content based on each subject's height. Starlix produced statistically significant decreases in fasting and postprandial glycemia compared to placebo.
A total of 3,566 patients were randomized in nine double-blind, placebo- or active-controlled studies 8 to 24 weeks in duration to evaluate the safety and efficacy of Starlix® (nateglinide). 3,513 patients had efficacy values beyond baseline. In these studies Starlix was administered up to 30 minutes before each of three main meals daily.
Starlix® Monotherapy Compared to Placebo
In a randomized, double-blind, placebo-controlled, 24-week study, patients with Type 2 diabetes with HbA1C ≥ 6.8% on diet alone were randomized to receive either Starlix (60 mg or 120 mg three times daily before meals) or placebo. Baseline HbA1C ranged from 7.9% to 8.1% and 77.8% of patients were previously untreated with oral antidiabetic therapy. Patients previously treated with antidiabetic medications were required to discontinue that medication for at least 2 months before randomization. The addition of Starlix before meals resulted in statistically significant reductions in mean HbA1C and mean fasting plasma glucose (FPG) compared to placebo (see Table 1). The reductions in HbA1C and FPG were similar for patients na´ve to, and those previously exposed to, antidiabetic medications.
In this study, one episode of severe hypoglycemia (plasma glucose < 36 mg/dL) was reported in a patient treated with Starlix 120 mg three times daily before meals. No patients experienced hypoglycemia that required third party assistance. Patients treated with Starlix had statistically significant mean increases in weight compared to placebo (see Table 1).
In another randomized, double-blind, 24-week, active- and placebo-controlled study, patients with Type 2 diabetes were randomized to receive Starlix (120 mg three times daily before meals), metformin 500 mg (three times daily), a combination of Starlix 120 mg (three times daily before meals) and metformin 500 mg (three times daily), or placebo. Baseline HbA1C ranged from 8.3% to 8.4%. Fifty-seven percent of patients were previously untreated with oral antidiabetic therapy. Starlix monotherapy resulted in significant reductions in mean HbA1C and mean FPG compared to placebo that were similar to the results of the study reported above (see Table 2).
Table 1: Endpoint results for a 24-week, fixed dose study
of Starlix® monotherapy
|Placebo||Starlix® 60 mg three times daily before meals||Starlix® 120 mg three times daily before meals|
|Change from baseline (mean)||+0.2||-0.3||-0.5|
|Difference from placebo (mean)||-0.5a||-0.7a|
|Change from baseline (mean)||+9.1||+0.4||-4.5|
|Difference from placebo (mean)||-8.7a||-13.6a|
|Change from baseline (mean)||-0.7||+0.3||+0.9|
|Difference from placebo (mean)||+1.0a||+1.6a|
|a p-value ≤ 0.004|
Starlix® Monotherapy Compared to Other Oral Antidiabetic Agents
In a 24-week, double-blind, active-controlled trial, patients with Type 2 diabetes who had been on a sulfonylurea for ≥ 3 months and who had a baseline HbA1C ≥ 6.5% were randomized to receive Starlix (60 mg or 120 mg three times daily before meals) or glyburide 10 mg once daily. Patients randomized to Starlix had significant increases in mean HbA1C and mean FPG at endpoint compared to patients randomized to glyburide.
In another randomized, double-blind, 24-week, active- and placebo-controlled study, patients with Type 2 diabetes were randomized to receive Starlix (120 mg three times daily before meals), metformin 500 mg (three times daily), a combination of Starlix 120 mg (three times daily before meals) and metformin 500 mg (three times daily), or placebo. Baseline HbA1C ranged from 8.3% to 8.4%. Fifty-seven percent of patients were previously untreated with oral antidiabetic therapy. Patients previously treated with antidiabetic medications were required to discontinue medication for at least 2 months before randomization. The reductions in mean HbA1C and mean FPG at endpoint with metformin monotherapy were significantly greater than the reductions in these variables with Starlix monotherapy (see Table 2). Relative to placebo, Starlix monotherapy was associated with significant increases in mean weight whereas metformin monotherapy was associated with significant decreases in mean weight. Among the subset of patients na´ve to antidiabetic therapy, the reductions in mean HbA1C and mean FPG for Starlix monotherapy were similar to those for metformin monotherapy (see Table 2). Among the subset of patients previously treated with other antidiabetic agents, primarily glyburide, HbA1C in the Starlix monotherapy group increased slightly from baseline, whereas HbA1C was reduced in the metformin monotherapy group (see Table 2).
Starlix® Combination Therapy
In the active and placebo-controlled study of metformin and Starlix described above, the combination of Starlix and metformin resulted in statistically significantly greater reductions in HbA1C and FPG compared to either Starlix or metformin monotherapy (see Table 2). Starlix, alone or in combination with metformin, significantly reduced the prandial glucose elevation from pre-meal to 2-hours post-meal compared to placebo and metformin alone.
In this study, one episode of severe hypoglycemia (plasma glucose ≤ 36 mg/dL) was reported in a patient receiving the combination of Starlix and metformin and four episodes of severe hypoglycemia were reported in a single patient in the metformin treatment arm. No patient experienced an episode of hypoglycemia that required third party assistance. Compared to placebo, Starlix monotherapy was associated with a statistically significant increase in weight, while no significant change in weight was observed with combined Starlix and metformin therapy (see Table 2).
In another 24-week, double-blind, placebo-controlled trial, patients with Type 2 diabetes with HbA1C ≥ 6.8% after treatment with metformin ( ≥ 1500 mg daily for ≥ 1 month) were first entered into a four week run-in period of metformin monotherapy (2000 mg daily) and then randomized to receive Starlix (60 mg or 120 mg three times daily before meals) or placebo in addition to metformin. Combination therapy with Starlix and metformin was associated with statistically significantly greater reductions in HbA1C compared to metformin monotherapy (-0.4% and -0.6% for Starlix 60 mg and Starlix 120 mg plus metformin, respectively).
Table 2: Endpoint results for a 24-week study of Starlix®
monotherapy and combination with metformin
|Placebo||Starlix® 120 mg three times daily before meals||Metformin 500 mg three times daily||Starlix® 120 mg before meals plus Metformin*|
|HbA1C (%) All||N=160||N=171||N=172||N=162|
|Change from baseline (mean)||+0.4||-0.4bc||-0.8c||-1.5|
|Difference from placebo||-0.8a||-1.2a||-1.9a|
|Change from baseline (mean)||+0.3||-0.7c||-0.8c||-1.6|
|Difference from placebo||-1.0a||-1.1a||-1.9a|
|Change from baseline (mean)||+0.6||+0.004 bc||-0.8c||-1.4|
|Difference from placebo||-0.6a||-1.4a||-2.0a|
|FPG (mg/dL) All||N=166||N=173||N=174||N=167|
|Change from baseline (mean)||+8.0||-13.1bc||-30.0c||-44.9|
|Difference from placebo||-21.1a||-38.0a||-52.9a|
|Weight (kg) All||N=160||N=169||N=169||N=160|
|Change from baseline (mean)||-0.4||+0.9bc||-0.1||+0.2|
|Difference from placebo||+1.3a||+0.3||+0.6|
|a p-value ≤ 0.05 vs. placebo
b p-value ≤ 0.03 vs. metformin
c p-value ≤ 0.05 vs. combination
* Metformin was administered three times daily
A 24-week, double blind multicenter, placebo-controlled trial was performed in patients with Type 2 diabetes not adequately controlled after a therapeutic response to rosiglitazone monotherapy 8 mg daily. The addition of Starlix (120 mg three times per day with meals) was associated with statistically significantly greater reductions in HbA1C compared to rosiglitazone monotherapy. The difference was -0.77% at 24 weeks. The mean change in weight from baseline was about +3 kg for patients treated with Starlix plus rosiglitazone vs about +1 kg for patients treated with placebo plus rosiglitazone.
In a 12-week study of patients with Type 2 diabetes inadequately controlled on glyburide 10 mg once daily, the addition of Starlix (60 mg or 120 mg three times daily before meals) did not produce any additional benefit.
Last reviewed on RxList: 9/7/2011
This monograph has been modified to include the generic and brand name in many instances.
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