Metformin remains the first option for treating diabetes because it is associated with significant reductions in both diabetes-related and all-cause mortality. Metformin is usually well tolerated and has the added benefit of not being linked with hypoglycaemia or weight gain, which is beneficial for patients with type 2 diabetes. 

Metformin should be continued for as long as possible, even if patients start to use insulin. This is because it works on the insulin resistance pathway and so lower doses of insulin will be required. 

Over the last decade, several new treatments have come onto the market so patients have a wider choice than just metformin, sulfonylurea and insulin. These new classes are: 

• Dipeptidyl peptidase (DPP)-4 inhibitors (gliptins) 
• Pioglitazone (thiazolidinediones)
• GLP-1 analogues (incretin mimetics)
• Sodium glucose co-transporter (SGLT)-2 inhibitors (gliflozins) €“ offered in combination with other medicines rather than on their own.

All of these medicines are effective, but they work in slightly different ways and have different side effects and effectiveness profiles. One thing that is lacking from most of these newer medicines is evidence of long-term safety, particularly from cardiovascular studies, although longer-term data are starting to emerge. It remains essential that adverse drug reactions are reported to the Yellow Card Scheme, even if these medicines are no longer designated black triangle. 

In the last few years, there have been reports of pancreatitis with DPP-4 inhibitors and GLP-1 mimetics. The Medicines and Healthcare Products Regulatory Agency (MHRA) has also issued warnings about the risk of diabetic ketoacidosis (DKA) and amputations with SGLT-2 inhibitors. In 2010, there was a market recall of the thiazolidinedione rosiglitazone due to concerns over cardiovascular safety. This left pioglitazone as the sole medicine in its class, but a range of cautions and contraindications are now associated with its use. 

You can find the monitoring guidelines in the summary of product characteristics (SPC). Some side effects, cautions and contraindications are class effects. Others are limited to a single medicine within the class. It is important to stay up to date with safety information by checking the SPCs of individual medicines regularly or by subscribing to the MHRA's free Drug Safety Update.