Oral medication (tablets)
A number of medicines are used to control blood glucose levels in people with diabetes. Except for insulin, which is given by injection, the majority of these medicines are tablets that are swallowed (taken orally). Oral diabetes medicines are used to treat type 2 diabetes only.
There are several classes of oral diabetes medicines in current use in the UK, and new treatments are being studied in clinical trials. The most commonly used tablet treatments are:
- Biguanides, of which the only tablet used is metformin.
- Sulphonylureas, such as chlorpropamide, glibenclamide, gliclazide, glipizide, glimepiride, gliquidone, tolbutamide.
- Prandial glucose regulators, nateglinide and repaglinide
- Alpha-glucosidase inhibitors, such as acarbose.
- Thiazolidinediones (also called ‘glitazones’ or ‘PPAR-gamma agonists’). These medications are not now widely used. Rosiglitazone has recently been withdrawn from the market and pioglitazone has also been the subject of recent concerns.
- Gliptins (also called ‘DPP-4 inhibitors’), such as sitagliptin, vildagliptin, saxagliptin and linagliptin.
In addition, several combination oral medicines are available that contain two diabetes drugs in one tablet.
Metformin (also called Glucophage)
- Metformin is a safe, effective, tried and tested tablet for the treatment of diabetes. It has been in use all over the world for many years and has been shown time and again to be effective in reducing blood glucose and reducing the risk of long-term complications of diabetes.
- When diet and exercise fail to control blood glucose then metformin is usually the first tablet to be introduced. It is particularly useful in people who are overweight since it does not cause weight gain.
- Metformin is safe. It has few side effects. It is unlikely to cause hypoglycaemia when administered without other glucose lowering tablets. Some people will experience gastrointestinal problems such as nausea, abdominal discomfort and diarrhoea. These side effects are not serious and may improve with time if the tablets are continued or if the dose is reduced and built up very slowly.
- Metformin should be taken with or after a meal. There is a long-acting version of metformin which can be taken once a day, usually with the main meal of the day.
- Metformin should not be used by people who have kidney problems caused by diabetes, and needs to be stopped for a short period of time in patients having operations or x-ray contrast medium. Ask your healthcare professional for advice.
- Sulphonylureas have also been used for many years to treat type 2 diabetes and have been shown to be effective in lowering blood glucose and reducing the long-term complications of diabetes.
- The most commonly used sulphonylureas are gliclazide (also called Diamicron), glipizide (Glibinese or Minodiab) and glimpepiride (Amaryl). Glibenclamide (Daonil or Euglucon) has a long duration of action and should not be given to elderly people as there is a greater risk of hypoglycaemia than with other sulphonylureas.
- Sulphonylureas work by stimulating the insulin releasing cells in the pancreas (beta cells) to produce more insulin.
- All sulphonylureas can cause hypoglycaemia (excessively low blood glucose), as well as nausea and stomach upsets. They may also cause a degree of weight gain.
Prandial Glucose Regulators
- Repaglinide (also called Prandin) and nateglinide (Starlix) stimulate insulin release from pancreatic beta cells, very much like sulphonylureas.
- They have a rapid onset and short duration of action and are given shortly before each meal to try to prevent the rise in glucose that occurs following eating.
- They can also cause hypoglycaemia (excessively low blood glucose).
- These agents are more expensive than sulphonylureas and are not widely used at present.
- Acarbose (also called Glucobay) works in the bowel on an enzyme called alpha-glucosidase. It works to slow the digestion and absorption of carbohydrate, which in turn lowers blood glucose.
- Acarbose does not cause hypoglycaemia (excessively low blood glucose) when used on its own, but it does often cause flatulence (wind) and diarrhoea which limits its use.
- Patients who take acarbose and other agents which may cause hypoglycaemia such as sulphonylureas or insulin MUST treat the hypoglycaemia with GLUCOSE and not SUCROSE (sugar). If you are in any doubt about this please seek advice from your healthcare professional.
- Thiazolidinedione tablets are now been restricted in their use: rosiglitazone (also called Avandia) has now been withdrawn from the market mainly due to a studies showing it may increase the risk of heart attacks. Pioglitazone (Actos) is being investigated because of potential links to bladder cancer but is still a useful tablet for certain people in certain situations.
- These tablets increase the action of insulin and therefore reduce blood glucose levels.
- Thiazolidinediones can cause retention of fluid leading to ankle swelling, breathlessness and a gain in weight. These tablets should not be taken by people who have had heart failure.
- These are a relatively new type of tablet called gliptins or dipeptidylpeptidase-4 (DPP-4) inhibitors.
- There are currently four DPP-4 inhibitors available, sitagliptin (also known as Januvia), vildagliptin (Galvus), saxagliptin (Onglyza) and linagliptin (Trajenta).
- DPP-4 inhibitors act by increasing levels of hormones called 'incretins' or GLP-1. This has a resulting effect of increasing release of insulin from the beta cells in the pancreas and also reducing production of a hormone called glucagon, both of which reduce blood glucose levels.
- These tablets lower blood glucose but their effects on the long-term complications of diabetes are not yet known.
- These tablets are proving increasingly popular because they are well tolerated and lower blood sugar levels without causing any increase in weight.