Metformin vs. Januvia

• Metformin and Januvia (sitagliptin) are oral medications that lower blood glucose (sugar) and are used to treat type 2 diabetes.
• Metformin is also used to treat polycystic ovaries and weight gain due to medications used for treating psychoses.
• Brand names of metformin include Glumetza, Glucophage, and Fortamet.
• Side effects of metformin and Januvia that are similar include nausea and diarrhea.
• Side effects of metformin that are different from Januvia include vomiting, gas, bloating, and loss of appetite.
• Side effects of Januvia that are different from metformin include upper respiratory tract infection, headache, and abdominal pain.

Metformin is an oral medication that lowers blood glucose (sugar) and is used for treating type 2 diabetes. Metformin increases the sensitivity of liver, muscle, fat, and other tissues to the uptake and effects of insulin, which lowers the sugar levels in the blood. Metformin does not increase the concentration of insulin in the blood and does not cause excessively low blood glucose levels (hypoglycemia) when used alone. Metformin can reduce complications of diabetes such as heart disease, blindness, and kidney disease. Metformin is also used to treat polycystic ovaries and weight gain due to medications used for treating psychoses.

Januvia (sitagliptin) is an oral drug that reduces blood sugar (glucose) levels in patients with type 2 diabetes. Januvia is a DPP-4 inhibitor. Other drugs in this class include saxagliptin (Onglyza) and linagliptin (Tradjenta). Januvia works to reduce blood glucose levels by inhibiting the DPP-4 enzyme and increasing the levels of the hormones GLP-1 and GIP.

Metformin

The most common side effects with metformin are

• nausea,
• vomiting,
• gas,
• bloating,
• diarrhea and
• loss of appetite.

These symptoms occur in one out of every three patients. These side effects may be severe enough to cause therapy to be discontinued in one out of every 20 patients. These side effects are related to the dose of the medication and may decrease if the dose is reduced.

Metformin may also cause:

• weakness or lack of energy
• respiratory tract infections,
• low levels of vitamin B-12,
• low blood glucose (hyperglycemia)
• constipation,
• indigestion, muscle pain,
• heartburn, and
• chills.

A serious but rare side effect of metformin is lactic acidosis. Lactic acidosis occurs in one out of every 30,000 patients and is fatal in 50% of cases. The symptoms of lactic acidosis are

• weakness,
• trouble breathing,
• abnormal heartbeats,
• unusual muscle pain,
• stomach discomfort,
• light-headedness, and
• feeling cold.

Patients at risk for lactic acidosis include those with reduced function of the

• kidneys or liver,
• congestive heart failure,
• severe acute illnesses, and
• dehydration.

Januvia

The most common side effects of sitagliptin are:

• upper respiratory tract infection and
• headache.

Other important side effects of sitagliptin include:

• abdominal pain,
• nausea and
• diarrhea.

There have been reports of fatal and non-fatal pancreatitis following use of sitagliptin. Acute kidney failure and severe hypersensitivity reactions have also been reported during treatment with sitagliptin.

Metformin

• For treating type 2 diabetes in adults, metformin (immediate release) usually is begun at a dose of 500 mg twice a day or 850 mg once daily. The dose is gradually increased by 500 mg weekly or 850 mg every two weeks as tolerated and based on the response of the levels of glucose in the blood. The maximum daily dose is 2550 mg given in three divided doses.
• If extended tablets are used, the starting dose is 500 mg or 1000 mg daily with the evening meal. The dose can be increased by 500 mg weekly up to a maximum dose of 2000 mg except for Fortamet (2500 mg of Fortamet, once daily or in two divided doses). Glumetza tablets (500 -1000mg formulations are given once daily (either 1000 to 2000mg). Fortamet and Glumetza are modified release formulations of metformin. Metformin should be taken with meals.
• For pediatric patients 10-16 years of age, the starting dose is 500 mg twice a day. The dose can be increased by 500 mg weekly up to a maximum dose of 2000 mg in divided doses.
• Children older than 17 years of age may receive 500 mg of extended release tablets daily up to a maximum dose of 2000 mg daily. Extended release tablets are not approved for children younger than 17 years of age.
• Metformin-containing drugs may be safely used in patients with mild to moderate renal impairment. Renal function should be assessed before starting treatment and at least yearly.
• Metformin should not be used by patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2 and starting metformin in patients with an eGFR between 30-45 mL/minute/1.73 m2 is not recommended.
• Metformin should be stopped at the time of or before administering iodinated contrast in patients with an eGFR between 30 and 60 mL/minute/1.73 m2; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Kidney function should be evaluated 48 hours after receiving contrast and metformin may be restarted if kidney function is stable.

Januvia

• Sitagliptin may be taken with or without food. The recommended dose is 100 mg once daily. Renal function should be assessed prior to starting sitagliptin and periodically during treatment. The dose of sitagliptin should be modified based on renal function.

Metformin

• Cimetidine (Tagamet), by decreasing the elimination of metformin from the body, can increase the amount of metformin in the blood by 40%. This may increase the frequency of side effects from metformin.
• Ioversol (Optiray) and other iodinated contrast media may reduce kidney function, which reduces elimination of metformin, leading to increased concentrations of metformin in the blood. Metformin should be stopped 48 hours before and after use of contrast media.
• Thiazide diuretics, steroids, estrogens, and oral contraceptives may increase blood glucose and reduce the effect of metformin. When these drugs are stopped, patients should be closely observed for signs of low blood glucose.
• Alcohol consumption increases the effect of metformin on lactate production, increasing the risk of lactic acidosis.

Januvia

• Sitagliptin may slightly increase the concentration of digoxin (Lanoxin) in the body when both drugs are being taken. Digoxin concentrations should be monitored appropriately. The occurrence of low blood glucose increases when sitagliptin is combined with a sulfonylurea (for example, glyburide [Micronase, Diabeta, Glynase, Prestab]) or insulin. The dose of insulin or sulfonylurea should be reduced.

Metformin

• There are no adequate studies in pregnant women. Most experts agree that insulin is the best treatment for pregnant women with diabetes.
• Metformin is excreted into breast milk and can, therefore, be transferred to the nursing infant. Nursing mothers should not use metformin.

Januvia

• There are no adequate studies of sitagliptin in pregnant women.
• It is unknown whether sitagliptin is secreted in human breast milk.