An extra 3.5 million prescriptions were handed out to Scottish patients last year.
The increase comes following the Scottish Government’s abolition of the £3 charge for medication.
NHS Forth Valley has the third highest prescription cost per person in the country, with the health board area spending £230 for every person registered with a GP.
Conservative MSP for Central Scotland, Margaret Mitchell, slammed the figures.
She said: “The increase in providing free prescriptions is simply unsustainable when the health budget is under so much stress.
“Hundreds of thousands of people across Scotland are more than happy to pay something towards prescriptions.
“Clearly the cost of this policy is spiralling out of control.”
The SNP initiative was brought into force in April 2011, despite opposition from the Conservative and Lib Dem parties.
Prescriptions now cost the NHS in Scotland £1.8 billion, an increase of £36.5 million from last year.
A spokesperson for NHS Forth Valley said: “NHS Forth Valley has implemented a range of initiatives designed to reduce our prescribing costs per person and bring them in line with the Scottish average.
“Examples include prescribing more cost effective alternatives to certain medications without compromising patient care, and reviewing medications in line with evidence in specific clinical areas, particularly cardiovascular.
“This work is making a significant difference as currently our prescribing cost per patient is reducing at a greater rate than in other health board areas.”
Currently those in England pay £7.20 for a prescription, but they are free in Wales and Northern Ireland.