Janumet (Sitagliptin, metformin)
How does it work?
Janumet tablets contain two active ingredients, metformin and sitagliptin. These are both medicines used to help control blood sugar levels in people with type 2 diabetes.
People with diabetes mellitus have a deficiency or absence of a hormone produced by the pancreas called insulin. Insulin is the main hormone responsible for the control of sugar (glucose) in the blood. In type 2 diabetes the pancreas does not produce sufficient insulin, and the cells of the body are resistant to the low levels of insulin circulating in the blood. Insulin would normally make the cells remove sugar from the blood; hence in type 2 diabetes blood sugar levels can rise too high.
Metformin is a type of antidiabetic medicine known as a biguanide. It works in a number of ways to decrease the amount of sugar in the blood. Firstly, it reduces the amount of sugar produced by cells in the liver. Secondly, it increases the sensitivity of muscle cells to insulin. This enables these cells to remove sugar from the blood more effectively. Finally, it also delays absorption of sugar from the intestines into the bloodstream after eating.
Sitagliptin is a type of antidiabetic medicine known as a dipeptidyl peptidase-4 (DPP-4) inhibitor. It helps to reduce blood sugar levels by preventing the breakdown of two incretin hormones, called glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP). These hormones are normally produced naturally by the body in response to food intake. They stimulate the pancreas to produce insulin in response to increasing levels of glucose in the blood, and they also reduce the production of glucagon, which is a hormone that normally increases glucose production by the liver. These actions help control blood sugar levels.
This combination of medicines helps control blood sugar levels both directly after meals and between meals.
What is it used for?
Janumet tablets are licensed for use in people with type 2 diabetes whose blood sugar is not controlled by the maximum tolerated dose of metformin alone, or who are already taking metformin and sitagliptin as separate tablets.
They are also licensed for use in combination with a sulphonylurea (eg gliclazide) or a glitazone (eg pioglitazone), when one of these combined with metformin has not controlled blood sugar well enough. Janumet tablets may also be used in combination with insulin.
How do I take it?
- Janumet tablets are usually taken twice a day, morning and evening.
- The tablets should be taken with a meal.
- If you forget to take a dose of this medicine, take it with your next meal, unless you were due to take a tablet then anyway. Do not take a double dose to make up for a forgotten tablet.
- It is important that you continue to follow the diet and exercise advice given to you by your doctor or nurse while you are using this medicine. This medicine only helps to control your blood sugar levels and should not be used as a substitute for eating healthily and taking regular exercise.
- Hypoglycaemia (low blood glucose) has been commonly reported when this medicine is used in combination with sulphonylurea medicines, eg gliclazide or glibenclamide, or with insulin. Symptoms of hypoglycaemia usually occur suddenly and may include cold sweats, cool pale skin, tremor, anxious feeling, unusual tiredness or weakness, confusion, difficulty in concentration, excessive hunger, temporary vision changes, headache, nausea and palpitations. You should talk to your doctor or diabetes specialist about this and make sure you know what to do if you experience these symptoms.
- Your ability to concentrate or react may be reduced if you have low blood sugar, and this can cause problems driving or operating machinery. You should take precautions to avoid low blood sugar when driving - discuss this with your doctor. This medicine may also cause dizziness, and if affected you should take care when driving or operating machinery.
- Your doctor may want you to check your blood sugar level from time to time while you are taking this medicine. Make sure you discuss how to do this and how often with your GP, pharmacist or diabetes specialist.
- You should avoid drinking alcohol while you are taking this medicine, as it can increase the risk of low blood sugar (hypoglycaemia) and lactic acidosis (see below).
- Metformin can cause a rare but serious condition called lactic acidosis, which is an excess of lactic acid in the blood. It is more likely to occur in people with decreased kidney function. Drinking excessive amounts of alcohol while taking this medicine, particularly on an empty stomach or if you have liver problems, can also increase the risk of lactic acidosis. Your doctor will monitor you for this side effect, but symptoms that might indicate its development include rapid and/or deep breathing and non-specific symptoms such as feeling weak, sick or generally unwell, vomiting, abdominal pain, or unusual muscle pains or discomfort. You should stop taking this medicine and consult your doctor if you experience any of these.
- Your kidney function should be monitored regularly while you are taking this medicine. Your doctor will usually want to check your kidney function once or twice a year, or more frequently if you are elderly or have any existing kidney problems.
- Your doctor will ask you to stop taking this medicine temporarily if you are going to have a certain type of X-ray involving an injection of iodinated dye (contrast agent). Tell your doctor that you are taking this medicine if you are due to have this type of X-ray. You should not start taking this medicine again until 48 hours after the X-ray, and only after your kidney function has been tested and found to be normal.
- Consult your doctor about your diabetes treatment if you are due to have surgery under a general anaesthetic. In these situations blood sugar is normally controlled by insulin, so your doctor may ask you to stop taking this medicine 48 hours before surgery.
- A few cases of inflammation of the pancreas (acute pancreatitis) have been reported in people taking sitagliptin and other medicines of this type. Symptoms of pancreatitis include unexplained, persistent, severe abdominal pain, sometimes spreading to the back. You should tell your doctor if you experience these symptoms while taking this medicine, so they can be investigated.
Use with caution in
- People over 75 years of age.
Not to be used in
- Type 1 diabetes.
- Diabetic keto-acidosis.
- Diabetic pre-coma (due to ketoacidosis in severe and inadequately treated diabetes).
- Moderate to severely decreased kidney function.
- Decreased liver function.
- Heart failure.
- People who have recently had a heart attack.
- People with conditions that cause breathing to be ineffective, ie to not effectively oxygenate the blood or remove carbon dioxide from the lungs (respiratory failure).
- People with reduced blood flow to vital internal organs (shock).
- People with severe infections or blood poisoning (sepsis).
- Alcohol poisoning.
- This medicine is not recommended for children and adolescents under 18 years of age, because its safety and effectiveness have not been established in this age group.
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- The safety of sitagliptin for use during pregnancy has not been established. It should not be used during pregnancy. Diabetes mellitus is usually controlled using insulin during pregnancy, because this provides a more stable control of blood sugar. Metformin many also sometimes be used. However, as Janumet contains a combination of metformin and sitagliptin it should not be used during pregnancy. If you get pregnant while taking this medicine, or are planning a pregnancy, you should seek medical advice from your doctor.
- It is not known if sitagliptin passes into breast milk. Metformin does pass into breast milk. The manufacturer states that Janumet should not be used by breastfeeding mothers. Seek further medical advice from your doctor.
- Take this medication with or after food.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.
- Disturbances of the gut such as nausea, vomiting or abdominal pain, constipation, flatulence and diarrhoea.
- Metallic taste.
- Loss of appetite.
- Swelling of feet or ankles (peripheral oedema).
- Upper respiratory tract infection.
- Inflammation of the nose and throat, causing a blocked or runny nose and sore throat (nasopharyngitis).
- Dry mouth.
- Low blood sugar levels (hypoglycaemia - when used with a sulphonylurea or insulin). See warning section above.
- Skin reactions, such as redness, itching or rash.
- Elevated levels of lactic acid in the blood (lactic acidosis).
- Decreased absorption of vitamin B12 during long-term use.
- Inflammation of the liver (hepatitis).
- Inflammation of the pancreas (acute pancreatitis) - see warning section above.
- Inflammation of blood vessels (vasculitis).
- Severe blistering skin reaction affecting the tissues of the eyes, mouth, throat and genitals (Stevens-Johnson Syndrome).
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
Other side effects have been reported with both metformin and sitagliptin used on their own and are therefore possible with this combination product. You can read more about the possible side effects of the individual ingredients in the factsheets linked at the end of the page.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
When Janumet is taken with other antidiabetic medicines, such as sulphonylureas (eg gliclazide, glibenclamide) or insulin, there will be an enhanced blood sugar lowering effect. Your blood sugar level may need to be monitored if you are taking Janumet in combination with other antidiabetic medicines. Ask your doctor for advice.
Cimetidine and rilpivirine may increase the blood level of metformin, which could increase the risk of its side effects. Your doctor may need to reduce your dose of this medicine if you regularly take one of these medicines as well.
Medicines that increase blood sugar levels as a side effect may make this medicine less effective at controlling blood sugar. Medicines that can increase blood sugar levels include the following:
- antipsychotic medicines, such as chlorpromazine, olanzapine, risperidone
- beta-2-agonists, such as salbutamol, salmeterol
- corticosteroids, such as prednisolone
- oestrogens and progestogens, such as those contained in oral contraceptives
- thiazide diuretics, such as bendroflumethiazide.
Your doctor may want to monitor your blood sugar if you start or stop treatment with any of these while taking this medicine, and if necessary your doctor may alter your dose of this medicine.
Low blood sugar levels (hypoglycaemia) may occur, sometimes unpredictably, if disopyramide or ACE inhibitors such as captopril are taken with this medicine. Your doctor may want you to temporarily check your blood sugar more frequently if you start treatment with one of these while taking this medicine.
MAOI antidepressants, such as phenelzine, tranylcypromine or isocarboxazid, may enhance the blood sugar lowering effect of metformin. Your doctor may ask you to monitor your blood sugar more frequently if you are prescribed an MAOI antidepressant with this medicine.
A drop in the number of blood cells called platelets in the blood has been seen in some people taking the antihistamine ketotifen in combination with metformin. The manufacturer of ketotifen recommends that it should be avoided in people taking metformin.
Sitagliptin may cause a small increase in the amount of digoxin in the blood when both medicines are being taken together. If you are taking digoxin, your doctor may want you to have regular blood tests to monitor the amount of digoxin in your blood after you start treatment with this medicine.
Other medicines containing the same active ingredients
There are currently no other medicines available in the UK that contain both metformin and sitagliptin as the active ingredients.
Glucophage and Metsol contain just metformin, and metformin is also available on its own without a brand name, ie as the generic medicine.
Januvia tablets contain just sitagliptin.