Type 2 Diabetes, October 2012 and February 2013

Drug utilisation sub-committee (DUSC)

October 2012 and February 2013

Full report for Type 2 Diabetes (PDF 736 KB)
Full report for Type 2 Diabetes (Word 340 KB)

Summary

The natural history of type 2 diabetes means that most patients need anti-diabetic drugs in order to optimise blood glucose control and achieve good long-term health outcomes.

Drugs considered for listing on the Pharmaceutical Benefits Scheme (PBS) are assessed for effectiveness, safety, and cost-effectiveness compared to the therapy they are most likely to replace. Expected use and financial implications are also considered.

In recent years there have been a number of changes to the listing of drugs for type 2 diabetes on the PBS. These have included amended restrictions on the criteria for subsidisation of already listed drugs, additional indications for existing drugs, as well as the listing of new drugs. In addition, some safety concerns have arisen.

As use outside the PBS restrictions can affect the cost-effectiveness of the drugs (i.e. their value for money), the Drug Utilisation Sub-committee (DUSC) examined the utilisation and patterns of treatment of drugs for type 2 diabetes, and compared this use with current PBS restrictions. Drugs considered were the oral anti-diabetic drugs, metformin, sulfonylureas, dipeptidyl peptidase-4 inhibitors (known as gliptins), thiazolidinediones (known as glitazones) and acarbose; and the injectable anti-diabetic drugs, insulin and exenatide.

Patients eligible for an oral anti-diabetic drug on the PBS must start therapy on metformin or a sulfonylurea before using any other anti-diabetic drug (apart from insulin or acarbose). If blood glucose control isn’t achieved, a trial of metformin and a sulfonylurea in combination is required in most cases before any other therapies (apart from insulin) can be used. If glycaemic control is still not achieved, various criteria exist in relation to third line therapies. The gliptins, glitazones and exenatide are restricted PBS benefits and can only be prescribed in certain combinations to qualify for PBS subsidy (see full report for details).

The analysis presented in this report examined de-identified data from DUSC and the Department of Human Services (DHS) (Medicare) databases. The results show the use of drugs to manage type 2 diabetes is increasing: this is not surprising given the increasing prevalence of type 2 diabetes.

Metformin and the sulfonylureas were the most commonly prescribed oral anti-diabetic drugs. Metformin use has increased over time, as has use of fixed dose combination (FDC) products, basal insulin and the gliptins. Use of sulfonylureas overall has remained relatively stable. Acarbose use, which is low, has also been reasonably stable, with a recent, slight decline. Although exenatide has a broader PBS listing compared to the gliptins, use of exenatide is lower than the gliptins. As exenatide was only listed on the PBS in 2010, it may not yet have an established market. Use of glitazones is declining: safety concerns may be contributing to low and declining use.

Metformin remains the most common first line therapy for patients with type 2 diabetes. Metformin was the drug of choice for initiation of therapy for 62% of patients in 2003-2004, increasing to 79% of patients in 2009-2010. The high proportion of first line use with metformin is expected, as clinical guidelines recommend metformin as first line therapy and metformin has an unrestricted PBS listing.

The use of drugs in the first 3.5 years after starting therapy was analysed. In that period, most patients with type 2 diabetes did not need a second or third line drug. The analysis showed a small amount of use beyond the PBS restrictions in this time period. This use generally involved the addition of a second drug without a trial of both metformin and a sulfonylurea.

After considering the overall use of anti-diabetic therapies and the likelihood of some use beyond the PBS restrictions, particularly as patients progress beyond the first 3.5 years of treatment, DUSC asked for an additional analysis to be undertaken on third line agents. The analysis aimed to determine the proportion of use outside the PBS restrictions.

The analysis showed that nearly half (49%) of all patients starting on gliptin therapy had not taken metformin and a sulfonylurea in the 2-year period prior. This figure increased to 55% for patients starting on a gliptin and metformin in a FDC product.

The apparent high use of a gliptin with metformin in lieu of a sulfonylurea with metformin is concerning. Gliptins cost a lot more than sulfonylureas and are not PBS listed as an alternative to those drugs unless there is a contraindication or intolerance. The prevalence of true intolerance to sulfonylureas is low. Use outside the criteria for subsidisation is occurring more frequently with FDC products.

Overall, 28% of prevalent patients prescribed a gliptin, a glitazone or exenatide are prescribed it in a regimen of co-prescribed therapies that does not comply with PBS subsidy criteria.

• Pioglitazone (13% of pioglitazone users) has the least use beyond the PBS restriction of the third line therapies: rosiglitazone the highest (48% of rosiglitazone users). However total utilisation of rosiglitazone is very low and continues to decline.
• The use of a gliptin with both metformin and a sulfonylurea contributes the most to use outside PBS restrictions in terms of co-prescribed therapies. Some use of gliptin monotherapy is also evident. Gliptins are being used in a number of ways that have either not been considered or accepted to be cost-effective by the Pharmaceutical Benefits Advisory Committee (PBAC). The long-term safety of this relatively new class of agents has not been established and gliptins are of high cost compared to some of the therapies they are substituting in practice (such as sulfonylureas and pioglitazone).
• For exenatide, some use beyond PBS restrictions is apparent, mostly in combination with insulin. This indication has not been assessed as cost-effective by the PBAC.

The results of this analysis will be forwarded onto the Pharmaceutical Benefits Advisory Committee and the NPS MedicineWise for information.

This report was prepared by the Drug Utilisation Sub-committee (DUSC) of the PBAC.