14th November 2019, Dr Chee L Khoo
Oral therapy for T2D – navigating the PBS maze
During our recent GP Diabetes Injectable Masterclass Workshop, I noted that there was a lot of uncertainty and confusion in relation to what oral agents can be combined under the PBS. This uncertainty and confusion can only lead to hesitation to escalate treatment in patients whose glycaemic control is suboptimal. International guidelines now provide a suggested algorithm to guide us in determining the next agent or agents after metformin. Unfortunately, restrictions under the PBS are not always easy to reconcile with the international guidelines. So, let us try to clarify the spaghetti today.
Before we dive into the guidelines, we need to see what benefits each class of oral drugs confer in addition to it hypoglycaemic potency. Let’s concentrate on the four classes of agents that are commonly used beyond metformin – the DPP4 inhibitors, SGLT2 inhibitors, Thiazolidinediones (“glitazones”) and the old suplphonylureas. See Table 1 for their other effects.
The ADA/EASD Consensus statement of 2018 suggest that after metformin, we go through the series of questions:
- Is there atherosclerotic cardiovascular disease (ASCVD) risk? If there is, consider a GLP1-RA injectable first, an SGLT2 inhibitor if injectable not appropriate.
- Is there heart failure risk? – if there is consider an SGLT2 inhibitor first. If contraindicated, consider an GLP1-RA.
- Is there chronic kidney disease (CKD)? If there is, consider an SGLT2 inhibitor first. If contraindicated, consider an GLP1-RA.
- If there are no ASCVD, heart failure or CKD risks, is there a compelling reason to avoid hypoglycaemia? If there is, avoid a SU. Consider an SGLT2i, DPP4i, Glitazones or an GLP1-RA.
- If hypoglycaemia isn’t a problem, is there a compelling reason to avoid further weight gain? If there is consider an GLP1-RA or SGLT2 inhibitor first.
After you consider the options above, you then need to consider what the PBS allows us to do. It’s easy:
You can combine Metformin +/- Sulphonylurea (think about the above algorithm!) PLUS only one of the following class of agents:
We know that combining a DPP4i and SGLT2i achieve better glycaemic outcomes and as a result, the PBS allows us to use a DPP4i + SGLT2i combo. There are three brands that market the combo – QTERN (Saxagliptin + Dapagliflozin), Glyxambi (Linagliptin + Empaglifozin) and Steglujan (Sitagliptin + Ertugliflzin). Patients who are not able to tolerate metformin and/or sulphonylureas for whatever reasons, can be on the above agents alone.