Prescribing updates: July

The UK government has published a new drug safety update on the use of metformin and its effects on a patient's vitamin B12 levels.

The drug metformin is authorised for the treatment of type 2 diabetes mellitus and for use in patients who are at high risk of developing the disease. There are immediate-release and modified-release pills of metformin as well as an oral solution.

A common adverse effect of metformin therapy is now recognised to be decreased vitamin B12 levels, or vitamin B12 deficiency. This is especially true for patients receiving greater doses, being treated for longer periods of time or those whon hae preexisting risk factors. Therefore, patients using metformin who exhibit signs of vitamin B12 deficiency have been advised to have their serum levels of vitamin B12 checked. Additionally, it is suggested practioners consider routine monitoring for patients who have vitamin B12 insufficiency risk factors.

Recently, the MHRA and brand leader Glucophage (metformin) in Europe examined the known adverse medication reaction of vitamin B12 insufficiency. The MHRA determined that the product information for medications containing metformin needs to be revised following this study.