Glitazones for type 2 diabetes

‘Glitazones’ is the nickname given to a group of medicines called thiazolidinediones, which are used to treat type 2 diabetes. The glitazones are:

Pioglitazone and rosiglitazone are the active ingredients in these medicines.

Note about medicine names

Most medicines have two names: the active ingredient and the brand name. The active ingredient is the chemical in the medicine that makes it work. The brand name is the name given to the medicine by its manufacturer. There may be several brands that contain the same active ingredient. This website uses active ingredient names, with brand names in brackets. We also discuss medicines in groups or ‘classes’, when their effects or actions are very similar.


The glitazones are effective at lowering blood glucose but have not been used for long enough to know whether they also reduce the long-term complications of diabetes (such as heart disease and stroke). This will only become clear when they have been used by more people for longer periods of time.

Diabetes is a progressive condition. After a while, a single medicine will not be enough to control the levels of glucose in your blood. It could be months or years before this happens — but once it does another kind of diabetes medicine needs to be added to metformin (or a sulfonylurea) to control blood glucose levels.

Most commonly, people will start taking both metformin and a sulfonylurea when they need two medicines to control their blood glucose. However, some people can’t take this combination because they experience bad side effects, or they have a medical condition or another reason that means they can’t take metformin or a sulfonylurea (i.e. a contraindication). These people may have another kind of diabetes medicine added to their metformin (or sulfonylurea) instead.

The glitazones (pioglitazone and rosiglitazone) are one kind of diabetes medicine that can be used when this happens. They can be added to metformin or a sulfonylurea.

What do glitazones do?

Glitazones lower blood glucose levels by helping the body to use insulin better by reducing insulin resistance in the tissues of the body.

What are the benefits of taking a glitazone?

Pioglitazone or rosiglitazone may be taken on their own when diet and exercise alone don’t adequately control blood glucose levels. This may be a useful option, for example, if you are unable to take either metformin or a sulfonylurea.

Pioglitazone or rosiglitazone can also be given as a second medicine to people who are already taking either metformin or a sulfonylurea.

Pioglitazone can also be given to people who are already taking both metformin and a sulfonylurea if their blood glucose levels are still too high, and it can be used in combination with insulin.

Pioglitazone may reduce fats in the blood (triglycerides) more than rosiglitazone.

Note: Pioglitazone or rosiglitazone are only subsidised by the Pharmaceutical Benefits Scheme (PBS) if you are taking it together with metformin and/or a sulfonylurea, or with insulin.

The glitazones are a relatively new group of medicines and while they have been tested in clinical trials, all their benefits are not known.

Who can take a glitazone?

  • People with type 2 diabetes whose blood glucose is inadequately controlled by metformin or a sulfonylurea.
  • Pioglitazone (Actos) can be given to people already taking metformin and a sulfonylurea and to people using insulin.
  • Rosiglitazone (Avandia) cannot be given to people who are already taking both metformin and a sulfonylurea or to people using insulin as this increases the chances of heart failure or heart attack.

Glitazones may not be suitable for people with:

  • oedema (swelling due to fluid) as glitazones can also cause fluid build-up
  • osteoporosis
  • liver problems or kidney disease
  • eye problems caused by diabetes, such as fluid retention in the eye (diabetic macular oedema).

Glitazones are not suitable for people with:

Rosiglitazone is not suitable for people with heart disease because it may increase heart attacks.

Pioglitazone is not suitable for anyone with bladder cancer or any who has had bladder cancer.

What are the side effects of glitazones?

Because rosiglitazone (Avandia) and pioglitazone (Actos) are relatively new medicines, all of the side effects are not fully known. These will become clearer when glitazones have been used by more people for longer periods of time. Some new side effects have been discovered recently with these medicines.

Glitazones are known to commonly cause:

  • muscle pain
  • water retention and weight gain
  • headaches and dizziness
  • joint pain (arthralgia)
  • hypoglycaemia (low blood sugar)
  • lower iron (haemoglobin) levels in the blood.

Less frequently, bone fractures in women have been linked to glitazones.

In rare cases, glitazones can cause heart failure, liver damage, and fluid accumulation in the lungs (pulmonary oedema).

Rosiglitazone may increase the risk of a heart attack (myocardial infarction), fluid retention in the eye (diabetic macular oedema) that can affect vision, and increased levels of ‘bad’ LDL cholesterol.

Pioglitazone may slightly increase the risk of developing bladder cancer when used for more than 1 year.

Talk to your health professional if you have any concerns.

Click through the following links if you would like to read our brief information on rosiglitazone and pioglitazone written for health professionals.

Who else can I ask about side effects?

If you are concerned that you may have had side effects related to a medicine, seek medical advice or call the Adverse Medicines Events (AME) line on 1300 134 237 from anywhere in Australia (Mon–Fri, 9am–5pm) to report and discuss possible side effects.

Interactions

It is important to tell your health professional about all the medicines you are taking — including prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamins and minerals) — as they may interact with diabetes medicines and affect your blood glucose levels. This may mean that your doctor will need to adjust the dose of your glitazone, or make changes to your other medicines.

Some medicines are known to affect blood glucose levels. Click on the following links to view tables that list some of these medicines:

Apart from these, other medicines that may interact with pioglitazone and rosiglitazone include:*

  • some antibiotics (e.g. rifampicin and trimethoprim)
  • ketoconazole — used to treat fungal infections
  • gemfibrozil — a medicine given to some people to treat high cholesterol and fats (triglycerides) in the blood
  • non-steroidal anti-inflammatory medicines (NSAIDs), with the exception of low-dose aspirin
  • topiramate — used to treat epilepsy or migraine.

*As there are often many different brands of one medicine, we have only listed the active ingredient of the medicine here. To find out more, read our information about active ingredients and brand names.

Phone for medicines information

Call NPS Medicines Line on 1300 MEDICINE (1300 633 424) to get information about your prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamins and mineral supplements) from a pharmacist. Your call will be answered by healthdirect Australia.

References
  • Craig ME, Twigg SM, Donaghue KC, et al for the Australian Type 1 Diabetes Guidelines Expert Advisory Group. National evidence-based clinical care guidelines for type 1 diabetes in children, adolescents and adults. Canberra: Australian Government Department of Health and Ageing, 2011. www.diabetessociety.com.au/downloads/Type1guidelines14Nov2011.pdf (accessed 15 November 2011).
  • Rossi S, ed. eAMH [online]. Adelaide: Australian Medicines Handbook, July 2012.
  • Sweetman S, ed. Martindale: The complete drug reference [online]. London: Pharmaceutical Press. www.medicinescomplete.com/mc/martindale/current/ (accessed 18 October 2011).
  • Baxter K, ed. Stockley's drug interactions: A source book of interactions, their mechanisms, clinical importance and management. 9th edn. London: Pharmaceutical Press, May 2010. www.medicinescomplete.com/mc/stockley/current/ (accessed 18 October 2011).
  • The relevant consumer medicine information and product information have been consulted for every medicine discussed.