There is no convincing evidence that the newer class of diabetes drugs, known as glitazones, offer real advantages over other diabetes drugs, when used on their own, concludes the Drug and Therapeutics Bulletin (DTB).
The glitazones (pioglitazone and rosiglitazone), which are also used in combined double and triple therapy, now account for over half of the NHS spend on oral drugs for the regulation of blood sugar (glycaemic control).
New guidance on glitazones from the National institute for Health and Clinical Excellence (NICE) is expected next month.
An exhaustive trawl of the available evidence leads DTB to conclude that glitazones have a place in combined treatments with either metformin or a sulphonylurea people with type 2 diabetes who are unsuited to one or other of these older drugs.
But DTB makes it clear that there is "no convincing evidence" that when taken alone the glitazones produce greater health benefits than either of the other types of treatment.
"Evidence for their use in triple therapy is also weak, and they should be reserved for patients in whom insulin is contraindicated or is likely to be poorly tolerated," says DTB.
The drugs can have significant side effects, although the regulators still feel that the benefits outweigh the risks.
Heart failure is more common when treatment is combined with insulin.
And in 2007 the European medicines regulator, the EMEA, warned that patients with angina who had had certain types of heart attack should not be given rosiglitazone, and the drug was not recommended for those with ischaemic heart, or peripheral arterial, diseases.
And the US drugs regulator, the FDA, has also advised that rosiglitazone may increase the risk of a heart attack.
Heart failure is more common when glitazone treatment is combined with insulin, and research indicates higher rates of oedema (swelling) in both sexes and bone fractures in women.
DTB concludes that pioglitazone is probably the safer option of the two glitazones, but should still not be used in anyone at high risk of heart failure.
Although pioglitazone is licensed for use with insulin treatment, DTB says that this combination carries the risk of weight gain, oedema and potentially heart failure.