Collecting and destroying unused prescriptions is costing the NHS over £500,000 each year, according to figures obtained by the Liberal Democrats.
Ten out of 14 health boards responded to Freedom of Information requests which asked about the annual costs of removing and destroying prescription medicines that are returned unused to pharmacies in the area. The collective cost for these boards totalled £517,342.
In Glasgow, the cost was £120,000, while in Lothian £46,239 was spent in 2011/12, with 44 tonnes collected in 2011. Elsewhere, Grampian spent £70,638, collecting 36.4 tonnes of wastage in 2011, while Fife spent around £33,000 annually collecting approximately 19 tonnes.
Lib Dem health spokesman Jim Hume said these costs did not take into account the value of the medicines being wasted, or the cost of prescribing them in the first place.
He said many people were also throwing out unused prescriptions rather than returning them to the pharmacy.
"Across Scotland, colossal amounts of medicines are being wasted," he said. "Over 80 tonnes of unused medicines were collected from pharmacies in NHS Lothian and Grampian throughout the last year.
"The NHS is facing some of its toughest tests yet with an ageing population and in future years the NHS is going to have to do more with less. We must all do our part to ensure that every penny is used effectively and that wastage is reduced where possible."
Mr Hume added: "NHS staff need to regularly review the medicines that a patient is on. This is a proactive measure which could cut costs and improve health by ensuring patients are receiving appropriate treatment."
A Scottish Government spokeswoman said: "Reducing medicine waste is something everyone needs to be involved with, which is why health boards are working through local campaigns, GPs and pharmacies to make sure patients understand how and when to take their prescription.
"Through our Chronic Medication Service community pharmacists support people with long-term conditions and provide advice in taking their medication. GPs are also encouraged to prescribe in line with clinical guidelines and to ensure that requests for repeat medication are appropriately assessed and repeat prescriptions issued only where the individual items are actually needed."