Jones et al (1) criticise current guidelines, which highlight
possible contraindications to the use of metformin, as too vague and
potentially leading to underuse in patients with type 2 diabetes. Although
their desire for a “less ambiguous” approach seems sensible, their own
guidelines still lack clarity.
They note that any specific value of serum creatinine chosen as a cut
-off for prescription of metformin will be arbitrary, because of
variations in muscle mass and protein turnover. Despite this they then
select – for undefined reasons- a serum creatinine value of 150
micromols/L as the cut-off point in their guideline. They then suggest
“caution should therefore be used in prescribing metformin for elderly
patients”.
This is a vague statement, which could be interpreted as meaning that
metformin shouldn’t be prescribed at all in the elderly; that specialist
opinion should be sought or creatinine clearance calculated before it is
prescribed; or that renal function or serum lactate should be monitored
after it is prescribed.(2)
In addition, we are not informed of the authors' own definition of
“elderly”.
Given that the growing majority of patients with type 2 diabetes are
over the age of 65 years,and that there is already evidence of
undertreatment of such patients (3), it would seem particularly desirable
to be as clear as is possible about this age group, if the full benefits
of treatment are to be attained.
Although the simple formulae that can be used to estimate creatinine
clearance(4) are not completely reliable it may be preferable to suggest
that prescription is related to such a calculated estimate of clearance,
which takes into account patient age, rather than the serum creatinine
value alone.
Andrew T. Elder
Consultant Physician
Western General Hospital,
Edinburgh
1.Jones GC, Macklin JP, Alexander WD. Contraindications to the use of
metformin. BMJ 2003; 326: 4-5
2.Chehade JM, Mooradian AD in Diabetes in old age eds Sinclair
AJ,Finucane P. John Wiley,Chichester. 2001 p 202-3.
3.Hendra TJ,Sinclair AJ (1997) Improving the care of elderly diabetic
patients ; the final report of the St Vincent Joint Task Force for
Diabetes. Age and Ageing, 26 , 3-6.
4.Cockcroft, D.W. and Gault, M.H. (1976). Prediction of creatinine
clearance from serum creatinine. Nephron 16, 31.
Rapid Response:
Metformin in patients aged over 65 years.
Contraindications to the use of metformin.
Jones et al (1) criticise current guidelines, which highlight
possible contraindications to the use of metformin, as too vague and
potentially leading to underuse in patients with type 2 diabetes. Although
their desire for a “less ambiguous” approach seems sensible, their own
guidelines still lack clarity.
They note that any specific value of serum creatinine chosen as a cut
-off for prescription of metformin will be arbitrary, because of
variations in muscle mass and protein turnover. Despite this they then
select – for undefined reasons- a serum creatinine value of 150
micromols/L as the cut-off point in their guideline. They then suggest
“caution should therefore be used in prescribing metformin for elderly
patients”.
This is a vague statement, which could be interpreted as meaning that
metformin shouldn’t be prescribed at all in the elderly; that specialist
opinion should be sought or creatinine clearance calculated before it is
prescribed; or that renal function or serum lactate should be monitored
after it is prescribed.(2)
In addition, we are not informed of the authors' own definition of
“elderly”.
Given that the growing majority of patients with type 2 diabetes are
over the age of 65 years,and that there is already evidence of
undertreatment of such patients (3), it would seem particularly desirable
to be as clear as is possible about this age group, if the full benefits
of treatment are to be attained.
Although the simple formulae that can be used to estimate creatinine
clearance(4) are not completely reliable it may be preferable to suggest
that prescription is related to such a calculated estimate of clearance,
which takes into account patient age, rather than the serum creatinine
value alone.
Andrew T. Elder
Consultant Physician
Western General Hospital,
Edinburgh
1.Jones GC, Macklin JP, Alexander WD. Contraindications to the use of
metformin. BMJ 2003; 326: 4-5
2.Chehade JM, Mooradian AD in Diabetes in old age eds Sinclair
AJ,Finucane P. John Wiley,Chichester. 2001 p 202-3.
3.Hendra TJ,Sinclair AJ (1997) Improving the care of elderly diabetic
patients ; the final report of the St Vincent Joint Task Force for
Diabetes. Age and Ageing, 26 , 3-6.
4.Cockcroft, D.W. and Gault, M.H. (1976). Prediction of creatinine
clearance from serum creatinine. Nephron 16, 31.
Competing interests:
None declared
Competing interests: No competing interests