Sitagliptin And Metformin Hydrochloride

1 INDICATIONS AND USAGE ZITUVIMET is a combination of sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, and metformin hydrochloride (HCl), a biguanide, indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. ( 1 ) Limitations of Use: ZITUVIMET is not recommended in patients with type 1 diabetes mellitus. ( 1 ) ZITUVIMET has not been studied in patients with a history of pancreatitis. ( 1 ) ZITUVIMET is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Limitations of Use ZITUVIMET is not recommended in patients with type 1 diabetes mellitus. ZITUVIMET has not been studied in patients with a history of pancreatitis. It is unknown whether patients with a history of pancreatitis are at increased risk for the development of pancreatitis while using ZITUVIMET. [see Warnings and Precautions ( 5.2 )].

2 DOSAGE AND ADMINISTRATION Take ZITUVIMET orally twice daily with meals. ( 2.1 ) Individualize the dosage of ZITUVIMET on the basis of the patient's current regimen, effectiveness, and tolerability. ( 2.1 ) The maximum recommended daily dose is 100 mg of sitagliptin and 2,000 mg of metformin HCl. ( 2.1 ) The recommended starting dose in patients not currently treated with metformin is 50 mg sitagliptin and 500 mg metformin HCl twice daily, with gradual dose escalation recommended to reduce gastrointestinal side effects associated with metformin. ( 2.1 ) The starting dose in patients already treated with metformin should provide sitagliptin dosed as 50 mg twice daily (100 mg total daily dose) and the dose of metformin already being taken. For patients taking metformin HCl 850 mg twice daily, the recommended starting dose of ZITUVIMET is 50 mg sitagliptin and 1,000 mg metformin HCl twice daily. ( 2.1 ) Prior to initiation, assess renal function with estimated glomerular filtration rate (eGFR) ( 2.2 ) ○ Do not use in patients with eGFR below 30 mL/min/1.73 m 2 ○ ZITUVIMET is not recommended in patients with eGFR between 30 and less than 45 mL/min/1.73 m 2 . ZITUVIMET may need to be discontinued at time of, or prior to, iodinated contrast imaging procedures. ( 2.3 ) 2.1 Recommended Dosage Take ZITUVIMET orally twice daily with meals. Individualize the dosage of ZITUVIMET on the basis of the patient's current regimen, effectiveness, and tolerability. The maximum recommended daily dose is 100 mg of sitagliptin and 2,000 mg of metformin hydrochloride (HCl). Do not split or divide ZITUVIMET tablets. The recommended starting dose in patients not currently treated with metformin is 50 mg sitagliptin and 500 mg metformin HCl twice daily, with gradual dose escalation recommended to reduce gastrointestinal side effects associated with metformin. The starting dose in patients already treated with metformin should provide sitagliptin dosed as 50 mg twice daily (100 mg total daily dose) and the dose of metformin already being taken. For patients taking metformin HCl 850 mg twice daily, the recommended starting dose of ZITUVIMET is 50 mg sitagliptin and 1,000 mg metformin HCl twice daily. 2.2 Recommendations for Use in Renal Impairment Assess renal function prior to initiation of ZITUVIMET and periodically thereafter. ZITUVIMET is contraindicated in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/min/1.73 m 2 [see Contraindications ( 4 ) and Warnings and Precautions ( 5.1 )]. ZITUVIMET is not recommended in patients with an eGFR between 30 and less than 45 mL/min/1.73 m 2 because these patients require a lower dosage of sitagliptin than what is available in the fixed combination ZITUVIMET product. 2.3 Discontinuation for Iodinated Contrast Imaging Procedures Discontinue ZITUVIMET at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m 2 ; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure; restart ZITUVIMET if renal function is stable [see Warnings and Precautions ( 5.1 )].

6 ADVERSE REACTIONS The following adverse reactions are also discussed elsewhere in the prescribing information: Lactic Acidosis [see Warnings and Precautions ( 5.1 )] Pancreatitis [see Warnings and Precautions ( 5.2 )] Heart Failure [see Warnings and Precautions ( 5.3 )] Acute Renal Failure [see Warnings and Precautions ( 5.4 )] Vitamin B12 Deficiency [see Warnings and Precautions ( 5.5 )] Hypoglycemia with Concomitant Use with Insulin or Insulin Secretagogues [see Warnings and Precautions ( 5.6 )] Hypersensitivity Reactions [see Warnings and Precautions ( 5.7 )] Severe and Disabling Arthralgia [see Warnings and Precautions ( 5.8 )] Bullous Pemphigoid [see Warnings and Precautions ( 5.9 )] Most common adverse reactions (incidence ≥5% of patients simultaneously started on sitagliptin and metformin and more commonly than in patients treated with placebo were diarrhea, upper respiratory tract infection, and headache. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Zydus Pharmaceuticals (USA) Inc. at 1-877-993-8779 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Common Adverse Reactions Sitagliptin and Metformin Coadministration in Patients with Type 2 Diabetes Mellitus Inadequately Controlled on Diet and Exercise Table 1 summarizes the most common (≥5% of patients) adverse reactions reported in a 24-week placebo-controlled factorial trial in which sitagliptin and metformin were coadministered to patients with type 2 diabetes mellitus inadequately controlled on diet and exercise. Table 1: Sitagliptin and Metformin Coadministered to Patients with Type 2 Diabetes Mellitus Inadequately Controlled on Diet and Exercise: Adverse Reactions Reported in ≥5% of Patients Receiving Combination Therapy (and Greater than in Patients Receiving Placebo) Intent-to-treat population. Number of Patients (%) Placebo Sitagliptin 100 mg once daily Metformin HCl 500 mg/ Metformin HCl 1,000 mg twice daily Data pooled for the patients given the lower and higher doses of metformin. Sitagliptin 50 mg twice daily + Metformin HCl 500 mg/ Metformin HCl 1,000 mg twice daily N = 176 N = 179 N = 364 N = 372 Diarrhea 7 (4) 5 (2.8) 28 (7.7) 28 (7.5) Upper Respiratory Tract Infection 9 (5.1) 8 (4.5) 19 (5.2) 23 (6.2) Headache 5 (2.8) 2 (1.1) 14 (3.8) 22 (5.9) Sitagliptin Add-on Therapy in Patients with Type 2 Diabetes Mellitus Inadequately Controlled on Metformin Alone In a 24-week placebo-controlled trial of sitagliptin 100 mg administered once daily added to a twice daily metformin regimen, there were no adverse reactions in ≥5% of patients and more commonly than in patients given placebo. Discontinuation of therapy due to clinical adverse reactions was similar to the placebo treatment group (sitagliptin and metformin, 1.9%; placebo and metformin, 2.5%). Gastrointestinal Adverse Reactions The incidences of pre-selected gastrointestinal adverse experiences in patients treated with sitagliptin and metformin were similar to those reported for patients treated with metformin alone. See Table 2. Table 2: Pre-selected Gastrointestinal Adverse Reactions Reported in Patients with Type 2 Diabetes Mellitus Receiving Sitagliptin and Metformin Number of Patients (%) Trial of Sitagliptin and Metformin in Patients Inadequately Controlled on Diet and Exercise Trial of Sitagliptin Add-on in Patients Inadequately Controlled on Metformin Alone Placebo Sitagliptin 100 mg once daily Metformin HCl 500 mg/ Metformin HCl 1,000 mg twice daily Data pooled for the patients given the lower and higher doses of metformin. Sitagliptin 50 mg twice daily + Metformin HCl 500 mg/ Metformin HCl 1,000 mg twice daily Placebo and Metformin HCl ≥1,500 mg daily Sitagliptin 100 mg once daily and Metformin HCl ≥1,500 mg daily N = 176 N = 179 N = 364 N = 372 N = 237 N = 464 Diarrhea 7 (4) 5 (2.8) 28 (7.7) 28 (7.5) 6 (2.5) 11 (2.4) Nausea 2 (1.1) 2 (1.1) 20 (5.5) 18 (4.8) 2 (0.8) 6 (1.3) Vomiting 1 (0.6) 0 (0) 2 (0.5) 8 (2.2) 2 (0.8) 5 (1.1) Abdominal Pain Abdominal discomfort was included in the analysis of abdominal pain in the trial of initial therapy. 4 (2.3) 6 (3.4) 14 (3.8) 11 (3) 9 (3.8) 10 (2.2) Sitagliptin in Combination with Metformin and Glimepiride In a 24-week placebo-controlled trial of sitagliptin 100 mg as add-on therapy in patients with type 2 diabetes mellitus inadequately controlled on metformin and glimepiride (sitagliptin, N=116; placebo, N=113), the adverse reactions reported in ≥5% of patients treated with sitagliptin and more commonly than in patients treated with placebo were: hypoglycemia ( see Table 3) and headache (6.9%, 2.7%). Sitagliptin in Combination with Metformin and Rosiglitazone In a placebo-controlled trial of sitagliptin 100 mg as add-on therapy in patients with type 2 diabetes mellitus inadequately controlled on metformin and rosiglitazone (sitagliptin, N=181; placebo, N=97), the adverse reactions reported through Week 18 in ≥5% of patients treated with sitagliptin and more commonly than in patients treated with placebo were: upper respiratory tract infection (sitagliptin, 5.5%; placebo, 5.2%) and nasopharyngitis (6.1%, 4.1%). Through Week 54, the adverse reactions reported in ≥5% of patients treated with sitagliptin and more commonly than in patients treated with placebo were: upper respiratory tract infection (sitagliptin, 15.5%; placebo, 6.2%), nasopharyngitis (11%, 9.3%), peripheral edema (8.3%, 5.2%), and headache (5.5%, 4.1%). Sitagliptin in Combination with Metformin and Insulin In a 24-week placebo-controlled trial of sitagliptin 100 mg as add-on therapy in patients with type 2 diabetes mellitus inadequately controlled on metformin and insulin (sitagliptin, N=229; placebo, N=233), the only adverse reaction reported in ≥5% of patients treated with sitagliptin and more commonly than in patients treated with placebo was hypoglycemia (Table 3). Hypoglycemia In the above trials (N=5), adverse reactions of hypoglycemia were based on all reports of symptomatic hypoglycemia; a concurrent glucose measurement was not required although most (77%) reports of hypoglycemia were accompanied by a blood glucose measurement ≤70 mg/dL. When the combination of sitagliptin and metformin was coadministered with a sulfonylurea or with insulin, the percentage of patients reporting at least one adverse reaction of hypoglycemia was higher than that observed with placebo and metformin coadministered with a sulfonylurea or with insulin (Table 3). Table 3: Incidence and Rate of Hypoglycemia Adverse reactions of hypoglycemia were based on all reports of symptomatic hypoglycemia; a concurrent glucose measurement was not required: Intent-to-treat population. in Placebo-Controlled Clinical Trials of Sitagliptin in Combination with Metformin Coadministered with Glimepiride or Insulin Add-On to Glimepiride + Metformin (24 weeks) Sitagliptin 100 mg + Metformin + Glimepiride Placebo + Metformin + Glimepiride N = 116 N = 113 Overall (%) 19 (16.4) 1 (0.9) Rate (episodes/patient-year) Based on total number of events (i.e., a single patient may have had multiple events). 0.82 0.02 Severe (%) Severe events of hypoglycemia were defined as those events requiring medical assistance or exhibiting depressed level/loss of consciousness or seizure. 0 (0) 0 (0) Add-On to Insulin + Metformin (24 weeks) Sitagliptin 100 mg + Metformin + Insulin Placebo + Metformin + Insulin N = 229 N = 233 Overall (%) 35 (15.3) 19 (8.2) Rate (episodes/patient-year) 0.98 0.61 Severe (%) 1 (0.4) 1 (0.4) The overall incidence of reported adverse reactions of hypoglycemia in patients with type 2 diabetes mellitus inadequately controlled on diet and exercise was 0.6% in patients given placebo, 0.6% in patients given sitagliptin alone, 0.8% in patients given metformin alone, and 1.6% in patients given sitagliptin in combination with metformin. In patients with type 2 diabetes mellitus inadequately controlled on metformin alone, the overall incidence of adverse reactions of hypoglycemia was 1.3% in patients given add-on sitagliptin and 2.1% in patients given add-on placebo. In the trial of sitagliptin and add-on combination therapy with metformin and rosiglitazone, the overall incidence of hypoglycemia was 2.2% in patients given add-on sitagliptin and 0% in patients given add-on placebo through Week 18. Through Week 54, the overall incidence of hypoglycemia was 3.9% in patients given add-on sitagliptin and 1% in patients given add-on placebo. In an additional, 30-week placebo-controlled, trial of patients with type 2 diabetes mellitus inadequately controlled with metformin comparing the maintenance of sitagliptin 100 mg versus withdrawal of sitagliptin when initiating basal insulin therapy, the event rate and incidence of documented symptomatic hypoglycemia (blood glucose measurement ≤70 mg/dL) did not differ between the sitagliptin and placebo groups. Vital Signs and Electrocardiograms With the combination of sitagliptin and metformin, no clinically meaningful changes in vital signs or in ECG (including in QTc interval) were observed. Pancreatitis In a pooled analysis of 19 double-blind clinical trials that included data from 10,246 patients randomized to receive sitagliptin 100 mg/day (N=5,429) or corresponding (active or placebo) control (N=4,817), the incidence of acute pancreatitis was 0.1 per 100 patient-years in each group (4 patients with an event in 4,708 patient-years for sitagliptin and 4 patients with an event in 3,942 patient-years for control). Sitagliptin The most common adverse experience in sitagliptin monotherapy reported in ≥5% of patients and more commonly than in patients given placebo was nasopharyngitis. Metformin The most common (>5%) established adverse reactions due to initiation of metformin therapy are diarrhea, nausea/vomiting, flatulence, abdominal discomfort, indigestion, asthenia, and headache. Laboratory Tests Sitagliptin The incidence of laboratory adverse reactions was similar in patients treated with sitagliptin and metformin (7.6%) compared to patients treated with placebo and metformin (8.7%). In most but not all trials, a small increase in white blood cell count (approximately 200 cells/microL difference in WBC vs placebo; mean baseline WBC approximately 6,600 cells/microL) was observed due to a small increase in neutrophils. This change in laboratory parameters is not considered to be clinically relevant. Metformin In controlled clinical trials of metformin of 29 weeks duration, a decrease to subnormal levels of previously normal serum vitamin B 12 levels, without clinical manifestations, was observed in approximately 7% of patients. Such decrease, possibly due to interference with B 12 absorption from the B 12 -intrinsic factor complex, is, however, very rarely associated with anemia and appears to be rapidly reversible with discontinuation of metformin or vitamin B 12 supplementation. 6.2 Postmarketing Experience Additional adverse reactions have been identified during postapproval use of ZITUVIMET, sitagliptin, or metformin. Because these reactions are reported voluntarily from a population of uncertain size, it is generally not possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Skin and subcutaneous tissue disorders: hypersensitivity reactions including anaphylaxis, angioedema, rash, urticaria, cutaneous vasculitis, and exfoliative skin conditions including Stevens-Johnson syndrome; bullous pemphigoid; Respiratory, thoracic and mediastinal disorders: upper respiratory tract infection; Hepatobiliary disorders: hepatic enzyme elevations; cholestatic, hepatocellular, and mixed hepatocellular liver injury; Gastrointestinal disorders: acute pancreatitis, including fatal and non-fatal hemorrhagic and necrotizing pancreatitis [see Indications and Usage (1)]; constipation; vomiting; mouth ulceration; stomatitis; Renal and urinary disorders: worsening renal function, including acute renal failure (sometimes requiring dialysis) and tubulointerstitial nephritis; Musculoskeletal and connective tissue disorders: severe and disabling arthralgia; myalgia; pain in extremity; back pain; pruritus; rhabdomyolysis; Nervous system disorders : headache.

12.3 Pharmacokinetics Sitagliptin The pharmacokinetics of sitagliptin have been extensively characterized in healthy subjects and patients with type 2 diabetes mellitus. Following a single oral 100-mg dose to healthy volunteers, mean plasma AUC of sitagliptin was 8.52 µM•hr, C max was 950 nM, and apparent terminal half-life (t 1/2 ) was 12.4 hours. Plasma AUC of sitagliptin increased in a dose-proportional manner and increased approximately 14% following 100 mg doses at steady-state compared to the first dose. The intra-subject and inter-subject coefficients of variation for sitagliptin AUC were small (5.8% and 15.1%). The pharmacokinetics of sitagliptin was generally similar in healthy subjects and in patients with type 2 diabetes mellitus. Absorption Sitagliptin After oral administration of a 100 mg dose to healthy subjects, sitagliptin was rapidly absorbed with peak plasma concentrations (median T max ) occurring 1 to 4 hours postdose. The absolute bioavailability of sitagliptin is approximately 87%. Effect of Food Coadministration of a high-fat meal with sitagliptin had no effect on the pharmacokinetics of sitagliptin. Metformin The absolute bioavailability of a metformin HCl 500-mg tablet given under fasting conditions is approximately 50% to 60%. Studies using single oral doses of metformin HCl tablets 500 mg to 1,500 mg, and 850 mg to 2,550 mg (approximately 1.3 times the maximum recommended daily dosage), indicate that there is a lack of dose proportionality with increasing doses, which is due to decreased absorption rather than an alteration in elimination. Effect of Food Food decreases the extent of and slightly delays the absorption of metformin, as shown by approximately a 40% lower mean peak plasma concentration (C max ), a 25% lower area under the plasma concentration versus time curve (AUC), and a 35-minute prolongation of time to peak plasma concentration (T max ) following administration of a single 850-mg tablet of metformin HCl with food, compared to the same tablet strength administered fasting. The clinical relevance of these decreases is unknown. Distribution Sitagliptin The mean volume of distribution at steady state following a single 100-mg intravenous dose of sitagliptin to healthy subjects is approximately 198 liters. The fraction of sitagliptin reversibly bound to plasma proteins is low (38%). Metformin The apparent volume of distribution (V/F) of metformin following single oral doses of metformin HCl tablets 850 mg averaged 654 ± 358 L. Metformin is negligibly bound to plasma proteins, in contrast to sulfonylureas, which are more than 90% protein bound. Metformin partitions into erythrocytes, most likely as a function of time. At usual clinical doses and dosing schedules of metformin HCl tablets, steady-state plasma concentrations of metformin are reached within 24 to 48 hours and are generally <1 mcg/mL. Elimination Sitagliptin Approximately 79% of sitagliptin is excreted unchanged in the urine with metabolism being a minor pathway of elimination. The apparent terminal t 1/2 following a 100 mg oral dose of sitagliptin was approximately 12.4 hours and renal clearance was approximately 350 mL/min. Metformin Following oral administration, approximately 90% of the absorbed drug is eliminated via the renal route within the first 24 hours, with a plasma elimination half-life of approximately 6.2 hours. In blood, the elimination half-life is approximately 17.6 hours, suggesting that the erythrocyte mass may be a compartment of distribution. Metabolism Sitagliptin Following a [ 14 C] sitagliptin oral dose, approximately 16% of the radioactivity was excreted as metabolites of sitagliptin. Six metabolites were detected at trace levels and are not expected to contribute to the plasma DPP-4 inhibitory activity of sitagliptin. In vitro studies indicated that the primary enzyme responsible for the limited metabolism of sitagliptin was CYP3A4, with contribution from CYP2C8. Metformin Intravenous single-dose studies in normal subjects demonstrate that metformin is excreted unchanged in the urine and does not undergo hepatic metabolism (no metabolites have been identified in humans) nor biliary excretion. Excretion Sitagliptin Following administration of an oral [ 14 C] sitagliptin dose to healthy subjects, approximately 100% of the administered radioactivity was eliminated in feces (13%) or urine (87%) within one week of dosing. Elimination of sitagliptin occurs primarily via renal excretion and involves active tubular secretion. Sitagliptin is a substrate for human organic anion transporter-3 (hOAT-3), which may be involved in the renal elimination of sitagliptin. The clinical relevance of hOAT-3 in sitagliptin transport has not been established. Sitagliptin is also a substrate of p-glycoprotein (P-gp), which may also be involved in mediating the renal elimination of sitagliptin. However, cyclosporine, a P-gp inhibitor, did not reduce the renal clearance of sitagliptin. Metformin Elimination of metformin occurs primarily via renal excretion. Renal clearance is approximately 3.5 times greater than creatinine clearance, which indicates that tubular secretion is the major route of metformin elimination. Specific Populations Patients with Renal Impairment ZITUVIMET Studies characterizing the pharmacokinetics of sitagliptin and metformin after administration of ZITUVIMET in renally impaired patients have not been performed [see Dosage and Administration (2.2)]. Sitagliptin An approximately 2-fold increase in the plasma AUC of sitagliptin was observed in patients with moderate renal impairment with eGFR of 30 to less than 45 mL/min/1.73 m 2 , and an approximately 4-fold increase was observed in patients with severe renal impairment including patients with end-stage renal disease (ESRD) on hemodialysis, as compared to normal healthy control subjects. [see Dosage and Administration ( 2.2 )]. Metformin In patients with decreased renal function, the plasma and blood half-life of metformin is prolonged and the renal clearance is decreased [see Contraindications ( 4 ) and Warnings and Precautions ( 5.1 )]. Patients with Hepatic Impairment ZITUVIMET Studies characterizing the pharmacokinetics of sitagliptin and metformin after administration of ZITUVIMET in patients with hepatic impairment have not been performed. Sitagliptin In patients with moderate hepatic impairment (Child-Pugh score 7 to 9), mean AUC and C max of sitagliptin increased approximately 21% and 13%, respectively, compared to healthy matched controls following administration of a single 100-mg dose of sitagliptin. These differences are not considered to be clinically meaningful. There is no clinical experience in patients with severe hepatic impairment (Child-Pugh score >9) [see Use in Specific Populations ( 8.7 )]. Metformin No pharmacokinetic studies of metformin have been conducted in patients with hepatic impairment. Effects of Age, Body Mass Index (BMI), Gender, and Race Sitagliptin Based on a population pharmacokinetic analysis or a composite analysis of available pharmacokinetic data, BMI, gender, and race do not have a clinically meaningful effect on the pharmacokinetics of sitagliptin. When the effects of age on renal function are taken into account, age alone did not have a clinically meaningful impact on the pharmacokinetics of sitagliptin based on a population pharmacokinetic analysis. Elderly subjects (65 to 80 years) had approximately 19% higher plasma concentrations of sitagliptin compared to younger subjects. Metformin Limited data from controlled pharmacokinetic studies of metformin in healthy elderly subjects suggest that total plasma clearance of metformin is decreased, the half-life is prolonged, and C max is increased, compared to healthy young subjects. From these data, it appears that the change in metformin pharmacokinetics with aging is primarily accounted for by a change in renal function. Metformin pharmacokinetic parameters did not differ significantly between normal subjects and patients with type 2 diabetes mellitus when analyzed according to gender. Similarly, in controlled clinical studies in patients with type 2 diabetes mellitus, the antihyperglycemic effect of metformin was comparable in males and females. No studies of metformin pharmacokinetic parameters according to race have been performed. In controlled clinical studies of metformin in patients with type 2 diabetes mellitus, the antihyperglycemic effect was comparable in Whites (n=249), Blacks or African Americans (n=51), and Hispanics (n=24). Drug Interaction Studies ZITUVIMET Coadministration of multiple doses of sitagliptin (50 mg) and metformin HCl (1,000 mg) given twice daily did not meaningfully alter the pharmacokinetics of either sitagliptin or metformin in patients with type 2 diabetes mellitus. Pharmacokinetic drug interaction studies with ZITUVIMET have not been performed; however, such studies have been conducted with the individual components of ZITUVIMET (sitagliptin and metformin HCl). Sitagliptin In Vitro Assessment of Drug Interactions Sitagliptin is not an inhibitor of CYP isozymes CYP3A4, 2C8, 2C9, 2D6, 1A2, 2C19 or 2B6, and is not an inducer of CYP3A4. Sitagliptin is a P-gp substrate but does not inhibit P-gp mediated transport of digoxin. Based on these results, sitagliptin is considered unlikely to cause interactions with other drugs that utilize these pathways. Sitagliptin is not extensively bound to plasma proteins. Therefore, the propensity of sitagliptin to be involved in clinically meaningful drug-drug interactions mediated by plasma protein binding displacement is very low. In Vivo Assessment of Drug Interactions Effects of Sitagliptin on Other Drugs In clinical studies, sitagliptin did not meaningfully alter the pharmacokinetics of metformin, glyburide, simvastatin, rosiglitazone, digoxin, warfarin, or an oral contraception (ethinyl estradiol and norethindrone) (Table 5), providing in vivo evidence of a low propensity for causing drug interactions with substrates of CYP3A4, CYP2C8, CYP2C9, P-gp, and organic cationic transporter (OCT). Table 5: Effect of Sitagliptin on Systemic Exposure of Coadministered Drugs Coadministered Drug Dose of Coadministered Drug All doses administered as single dose unless otherwise specified. Dose of Sitagliptin Geometric Mean Ratio (ratio with/without sitagliptin) No Effect = 1 AUC AUC is reported as AUC 0-∞ unless otherwise specified. C max Digoxin 0.25 mg ‡ once daily for 10 days 100 mg Multiple dose. once daily for 10 days Digoxin 1.11 AUC 0-24hr. 1.18 Glyburide 1.25 mg 200 mg once daily for 6 days Glyburide 1.09 1.01 Simvastatin 20 mg 200 mg once daily for 5 days Simvastatin 0.85 AUC 0-last. 0.8 Simvastatin Acid 1.12 1.06 Rosiglitazone 4 mg 200 mg once daily for 5 days Rosiglitazone 0.98 0.99 Warfarin 30 mg single dose on day 5 200 mg once daily for 11 days S(-) Warfarin 0.95 0.89 R(+) Warfarin 0.99 0.89 Ethinyl estradiol and norethindrone 21 days once daily of 35 µg ethinyl estradiol with norethindrone 0.5 mg x 7 days, 0.75 mg x 7 days, 1 mg x 7 days 200 mg once daily for 21 days Ethinyl estradiol 0.99 0.97 Norethindrone 1.03 0.98 Metformin HCl 1,000 mg twice daily for 14 days 50 mg twice daily for 7 days Metformin 1.02 AUC 0-12hr. 0.97 Effects of Other Drugs on Sitagliptin Clinical data described below suggest that sitagliptin is not susceptible to clinically meaningful interactions by coadministered medications (Table 6). Table 6: Effect of Coadministered Drugs on Systemic Exposure of Sitagliptin Coadministered Drug Dose of Coadministered Drug All doses administered as single dose unless otherwise specified. Dose of Sitagliptin Geometric Mean Ratio (ratio with/without coadministered drug) No Effect = 1 AUC AUC is reported as AUC 0-∞ unless otherwise specified. C max Cyclosporine 600 mg once daily 100 mg once daily Sitagliptin 1.29 1.68 Metformin HCl 1,000 mg Multiple dose. twice daily for 14 days 50 mg twice daily for 7 days Sitagliptin 1.02 AUC 0-12hr. 1.05 Metformin HCl Table 7: Effect of Metformin HCl on Systemic Exposure of Coadministered Drugs Coadministered Drug Dose of Coadministered Drug All doses administered as single dose unless otherwise specified. Dose of Metformin HCl Geometric Mean Ratio (ratio with/without metformin) No Effect = 1 AUC AUC is reported as AUC 0-∞ unless otherwise specified. C max Cimetidine 400 mg 850 mg Cimetidine 0.95 AUC 0-24hr. 1.01 Glyburide 5 mg 500 mg GLUMETZA (metformin HCl extended-release tablets) 500 mg. Glyburide 0.78 Ratio of arithmetic means, p value of difference <0.05. 0.63 Furosemide 40 mg 850 mg Furosemide 0.87 0.69 Nifedipine 10 mg 850 mg Nifedipine 1.10 1.08 Propranolol 40 mg 850 mg Propranolol 1.01 0.94 Ibuprofen 400 mg 850 mg Ibuprofen 0.97 Ratio of arithmetic means. 1.01 Table 8: Effect of Coadministered Drugs on Systemic Exposure of Metformin HCl Coadministered Drug Dose of Coadministered Drug All doses administered as single dose unless otherwise specified. Dose of Metformin HCl Geometric Mean Ratio (ratio with/without coadministered drug) No Effect = 1 AUC AUC is reported as AUC 0-∞ unless otherwise specified. C max Glyburide 5 mg 500 mg GLUMETZA (metformin HCl extended-release tablets) 500 mg. Metformin 0.98 Ratio of arithmetic means. 0.99 Furosemide 40 mg 850 mg Metformin 1.09 1.22 Nifedipine 10 mg 850 mg Metformin 1.16 1.21 Propranolol 40 mg 850 mg Metformin 0.90 0.94 Ibuprofen 400 mg 850 mg Metformin 1.05 1.07 Drugs that are eliminated by renal tubular secretion may increase the accumulation of metformin. [see Warnings and Precautions (5.1) and Drug Interactions (7 )]. Cimetidine 400 mg 850 mg Metformin 1.40 1.61 Carbonic anhydrase inhibitors may cause metabolic acidosis [see Warnings and Precautions (5.1) and Drug Interactions (7) ]. Topiramate 100 mg Steady state 100 mg Topiramate every 12 hr + metformin HCl 500 mg every 12 hr AUC = AUC 0-12hr. 500 mg Metformin 1.25 1.17