JANUMET 50/850MG TAB

Indications

Approved Uses

As an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. [4, 25, 30]

Off-Label Uses

No widely accepted off-label use for the fixed-dose sitagliptin/metformin combination; metformin alone is used off-label for PCOS and diabetes prevention in high-risk patients.

Dosage & Administration

Dosing by Condition

Type 2 diabetes mellitus: typically 1 tablet (50/850) twice daily with meals when this strength is selected; choose starting strength based on current metformin dose/tolerability and titrate. Usual maximum daily dose: sitagliptin 100 mg/day and metformin 2000 mg/day.

Initial Dose

For patients not currently treated with metformin: 50 mg sitagliptin/500 mg metformin HCl twice daily. For patients already treated with metformin: sitagliptin 50 mg twice daily (100 mg total daily) plus current metformin dose. For patients taking metformin HCl 850 mg twice daily, recommended starting dose of JANUMET is 50 mg sitagliptin/1000 mg metformin HCl twice daily.

Maintenance Dose

One tablet twice daily, adjusted based on efficacy and tolerability. [5, 13]

Maximum Dose

100mg sitagliptin / 2000mg metformin per day (e.g., one 50mg/1000mg tablet twice daily). [9, 13, 27]

Children's Dosage

Not recommended for use in children and adolescents aged 10 to 17 years due to insufficient efficacy. [3, 4, 31]

Dose Adjustment Notes

Individualize dose and titrate metformin to minimize GI effects; assess eGFR before initiation and periodically. Contraindicated if eGFR <30 mL/min/1.73 m²; initiation not recommended if eGFR 30-45 and fixed-dose Janumet may be unsuitable when sitagliptin dose reduction is required. Temporarily withhold around iodinated contrast in at-risk patients and restart after renal function is stable.

How to Take

Take orally twice daily with meals; swallow the tablet whole with water. Do not crush, chew, or split.

Side Effects

Common Side Effects

Diarrhea, nausea, vomiting, abdominal discomfort, headache, and upper respiratory tract infection/nasopharyngitis; hypoglycemia mainly when combined with insulin or a sulfonylurea.

Side Effect Frequency

Common (≥1%): GI effects (diarrhea, nausea, vomiting, abdominal discomfort/flatulence/dyspepsia) and headache; nasopharyngitis/upper respiratory tract infection may occur; hypoglycemia mainly when combined with insulin or a sulfonylurea. Important but uncommon/rare: lactic acidosis (metformin; rare but serious), acute pancreatitis and hypersensitivity reactions (sitagliptin; uncommon/rare), severe arthralgia and bullous pemphigoid (rare), and decreased vitamin B12 with long-term metformin use.

Safety & Warnings

Contraindications

Contraindicated in: (1) severe renal impairment (eGFR <30 mL/min/1.73 m²), (2) acute or chronic metabolic acidosis including diabetic ketoacidosis, and (3) history of serious hypersensitivity reaction to sitagliptin or metformin.

Warnings & Precautions

Warnings/precautions: lactic acidosis risk (monitor renal function; withhold for iodinated contrast in at-risk patients and around surgery/procedures; stop if acidosis suspected), pancreatitis (stop if suspected), not for type 1 diabetes/DKA, hypersensitivity reactions (stop immediately), possible vitamin B12 deficiency with long-term metformin, and caution in heart failure/conditions predisposing to hypoxia or renal decline (e.g., elderly).

Drug Interactions

Interaction Severity

MAJOR/clinically significant: iodinated contrast media (metformin-risk of lactic acidosis in AKI; hold in appropriate patients), excessive alcohol (lactic acidosis risk), carbonic anhydrase inhibitors such as topiramate/acetazolamide (metabolic acidosis risk). MODERATE: insulin/sulfonylureas (hypoglycemia risk), cationic renally-secreted drugs e.g., cimetidine (↑ metformin exposure), drugs that worsen renal function or glycemic control (e.g., diuretics, corticosteroids). MINOR: digoxin (sitagliptin may slightly increase levels-monitor).

Food Interaction

Take with food (meals).

Special Populations

Children

Not recommended for use in children and adolescents aged 10 to 17 years due to insufficient efficacy. [3, 4, 31]

Elderly

Use with caution; renal function must be assessed before initiation and regularly thereafter due to age-related decline in renal function. Dose selection should be conservative. Contraindicated if eGFR <30 mL/min/1.73m².

Kidney Impairment

eGFR ≥45 mL/min/1.73 m²: no adjustment; eGFR 30-<45: initiation not recommended and fixed-dose JANUMET generally not recommended because a lower sitagliptin dose is required; eGFR <30: contraindicated.

Liver Impairment

Avoid use in patients with hepatic impairment (no dose adjustment recommended; generally not recommended due to lactic acidosis risk).

Storage & Patient Advice

Missed Dose

Take the missed dose as soon as remembered with food; if it is near the time of the next dose, skip the missed dose and resume the regular schedule. Do not double doses.

Stopping the Medicine

Do not stop JANUMET without consulting the prescriber; stopping may worsen glycemic control.

Overdose

Overdose may cause metformin-associated lactic acidosis (e.g., malaise, myalgias, respiratory distress, abdominal symptoms, hypothermia/hypotension/bradyarrhythmias); management is immediate medical evaluation, discontinue drug, supportive care, and consider hemodialysis to remove metformin.

Patient Counseling

Take JANUMET (sitagliptin/metformin) by mouth with meals to reduce GI upset; take it regularly and do not stop without medical advice. Avoid excessive alcohol (increases lactic acidosis risk). Tell your clinician before surgery or any iodinated contrast imaging-metformin-containing products are often held around contrast in patients at risk for kidney injury and restarted after renal function is reassessed. Seek urgent care for symptoms of lactic acidosis (e.g., unusual muscle pain, severe weakness, trouble breathing, abdominal pain with nausea/vomiting, dizziness, feeling cold). Report severe, persistent abdominal pain (possible pancreatitis) and any severe joint pain or blistering rash (rare DPP-4 inhibitor adverse effects). Hypoglycemia is uncommon with JANUMET alone but risk increases with insulin or sulfonylureas. Monitor renal function and glycemic control; consider periodic vitamin B12 monitoring with long-term metformin use.

Monitoring Requirements

Monitor glycemic control (SMBG as appropriate and HbA1c about every 3 months until stable then every 3-6 months), renal function (eGFR at baseline and at least annually; more often if at risk), vitamin B12 periodically with long-term metformin, and watch for pancreatitis symptoms; consider hepatic function assessment when clinically indicated.

Pharmacology

Mechanism of Action

Sitagliptin inhibits DPP-4, increasing endogenous incretins (GLP-1, GIP) to enhance glucose-dependent insulin secretion and suppress glucagon; metformin decreases hepatic glucose production, decreases intestinal glucose absorption, and improves insulin sensitivity.

Onset of Action

Sitagliptin: DPP-4 inhibition within hours (peak effect around 1-4 hours). Metformin: glucose-lowering begins within days, with full effect typically over 1-2 weeks (sometimes up to several weeks) as dose is titrated.

Duration of Effect

Sitagliptin provides ~24-hour DPP-4 inhibition (once-daily pharmacodynamic effect), while metformin’s glucose-lowering effect is maintained with regular dosing; the combination is dosed twice daily for the immediate-release metformin component.

Half-Life

Sitagliptin: terminal t1/2 ~12 hours (commonly reported ~8-14 hours). Metformin (immediate-release component): plasma t1/2 ~6 hours; whole-blood t1/2 ~17 hours due to erythrocyte distribution.

Bioavailability

Sitagliptin: ~87%. Metformin: 40-60%. [1, 14]

Metabolism

Sitagliptin: minimal metabolism (minor CYP3A4 and CYP2C8 involvement); Metformin: not metabolized (excreted unchanged).

Excretion

Sitagliptin: primarily renal elimination, ~87% recovered in urine as unchanged drug. Metformin: eliminated unchanged in urine (predominantly via active tubular secretion), with the majority excreted within ~24 hours.

Protein Binding

Sitagliptin: low protein binding ~38%. Metformin: negligible/essentially no plasma protein binding.

Product Information

Available Dosage Forms

Tablet (immediate-release, film-coated).

Composition per Dose

Each tablet: 50mg sitagliptin (as sitagliptin phosphate monohydrate) + 850mg metformin hydrochloride

Diabetes Type

Type 2

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