Date: 11th December, 2014
Oak House
Moorhead Way
Bramley
Rotherham
South Yorkshire
S66 1YY
Peter.magirr@nhs.net
(0114)3051330
Pharmacy Local Professional Network: South Yorkshire & Bassetlaw
Dear Colleague
Management of Stock Shortages
We are increasingly seeing problems with the availability of prescribed medicines, causing problems
for patients and increased demands upon clinicians.
This issue has been discussed within the Local Professional Network (LPN) for pharmacy and some
guidance produced relating to the drug metformin SR 500mg. Some of the guidance is generic in
terms of how to deal with shortages and some specific to metformin.
Please note that this guidance is general, has been produced for rapid and timely dissemination via
the LPN and may not be suitable for all patients; clinicians may therefore choose to use it as part of
their approach to care – but must ensure its applicability on an individual basis.
Yours sincerely
Peter Magirr BSc MSc MBA PhD FRPharmS
Chair: Pharmacy Local Professional Network.
NHS England (South Yorkshire and Bassetlaw)
Community Pharmacy Management of Stock Shortages
Metformin SR 500mg Tablets
There are currently supply problems with the slow release preparation of metformin 500mg
tablets, which will potentially remain unresolved in the near term. This guidance is
intended to help community pharmacy manage the situation to alleviate any problems for
patients and give advice to prescribers.
General Principles of Stock Shortage Management
 Take an active role in managing patients when stock shortages arise. It is not
acceptable to instruct a patient to try another pharmacy or refer them back to a
surgery without contacting that establishment first and agreeing a solution
 Gather all the information you need before making any decisions.
o How long is the shortage likely to last?
o Does the patient have a supply and how long will it last?
o Do any other local pharmacies have supplies?
o What are the suitable alternatives available?
o Are there any clinical and patient factors that may affect the use of alternatives?
Clinical Aspects of Metformin Therapy
Metformin is the only available and has a unique mode of action that is different to other
hypoglycaemic agents. It works mainly by decreasing gluconeogenesis and by increasing
peripheral utilization of glucose. Metformin is only effective if there are some residual
functioning pancreatic islet cells and only has a glucose lowering effect in the presence of
insulin. The dose usually starts at 500mg OD and is gradually increased over a number of
weeks up to 2g daily, according to response. Doses above 2g are licensed for the normal
release preparation, but are rarely tolerated and do not usually bring additional benefit
Side Effects
About 5% patients will not be able to tolerate metformin and will cease therapy as a result.
The usual intolerance is gastrointestinal, which can be minimized by starting at low dose
and titrating slowly. The effects are usually transient and will improve if the patient can
persist with treatment. There is some weak evidence that the slow release preparations
are better tolerated than the normal release.
Lactic acidosis is a rare condition that can occur, but is usually associated with other
medical factors. NICE recommends that patients with renal impairment and an eGFR of <
45 ml/min/1.73m2 are treated with caution at reduced doses and that metformin is avoided
in all patients with an eGFR < 30 ml/min/1.73m2. Conditions that increase the risk of tissue
hypoxia e.g. recent myocardial infarction, sepsis, hypotension, severe hepatic impairment,
can also increase the risk and so metformin should be used with caution
Hypoglycaemia is not usually an issue with metformin when used as monotherapy, as it
does not affect the secretion of insulin, which it requires to work. However caution should
be shown where other hypoglycaemic agents are being used.
Possible Strategies
Once need and lack of availability of Metformin SR 500mg Tablets is established possible
solutions could be:
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Change to normal release Metformin 500mg Tablets. This could potentially lead to a
greater incidence of gastrointestinal upset, but since the patient is already established
on the drug, tolerance may have developed. Taking the medicine with food and giving
reassurance that problems will ease, may help the situation. It is also worth
remembering that not all patients may have tried the normal release in the first
instance. Make sure the patient is counseled on how to take the new product as it is
often given as a split dose, whereas the slow release is once daily
Use the slow release 750mg and 1000mg strengths to make up to an equivalent daily
dose, or as close as possible. Patients who tolerate the drug well and are on
monotherapy could generally tolerate an increase in dose, if this is necessary. Caution
would need to be shown in patients with renal impairment, co-morbidities increasing
the chance of hypoxia and where other hypoglycaemic agents are being used. In the
latter patient group, enquire if hypoglycaemic episodes have been an issue. Where
problems exist, tend to recommend a rounding down of total daily dose, where
possible. The slow release preparation is sometimes given as a split dose in an attempt
to gain better glycaemic control. Try to maintain a split where possible.
Where the above strategies have failed, suggesting that diet alone should be used to
control the condition may be appropriate for patients who are just above target, for a
short period of time
Suggesting alternative agents should only be used where stock shortages are long
term, other strategies have failed and glucose control is paramount. This will require
attendance at a diabetes clinic and so should only be a last resort