Your correspondent raises several points about prescription charges and repeat prescriptions (Letters, October 6).

GPs in Brighton and Hove prescribe medicines with a total cost of approximately £40 million pounds each year. The average cost to the NHS of each prescription is £11.30.

From local surveys, it is estimated up to £1 million of these prescribed medicines are not used, and are returned to pharmacies for destruction. Common reasons for returning unwanted medicines are changes in the prescription and too much stock at home.

It is also worth noting the NHS has to bear the cost of secure collection and destruction of these unwanted medicines.

Pharmacists can never re-issue returned medicines, even if they are within their expiry date, as their safety and quality cannot be guaranteed once they have left the pharmacy.

Research has shown that when 28-day supplies are prescribed, the amount of wastage is reduced by about a third. For these reasons, we recommend that GPs should consider prescribing 28 or 56-day supplies for most patients on long-term medication.

However, this is not a "directive" and GPs can and should use their discretion and clinical judgement to determine the best length of supply in individual cases.

A reduction in the length of treatment per prescription is certainly not being used as a way of increasing revenue from prescription charges.

We encourage GPs to be mindful of the effects of increasing the costs to those patients who pay the prescription charge when they make changes to the length of repeat prescriptions.

Regular reviews are important to ensure patients are still on the best treatment for their condition.

The GP will specify how many months the repeat prescriptions can be issued before the patient has to come in for a check-up (this should not directly affect the length of treatment prescribed at any one time).

Most patients should have their medication reviewed about once a year but for older people, and those on several medicines, once every six months may be more appropriate.

-Jane Moffatt, head of medicines management, Brighton and Hove City Primary Care Trust