Generally, a prescription drug becomes a candidate for over the counter availability if it is used for a non-chronic condition that is relatively easy to self-diagnose and has low potential for harm from abuse.
Yet recent switches, such as the cholesterol-lowering drug simvastatin in the United Kingdom, do not fit this description.
The authors suggest that switches are motivated mainly by three factors: pharmaceutical firms' desire to expand their market, attempts to reduce drug bills, and the self care movement.
Much has been said about the UK Healthcare Products Regulatory Agency's controversial decision in May 2004 to reclassify simvastatin 10mg as an over the counter medicine, as there have been no clinical trials of over the counter statins for prevention of heart disease.
Concern has been raised that the main motive behind the government's decision to allow simvastatin to be sold directly to the public is to save NHS costs. But this is unlikely because high risk patients will still be eligible for statins on prescription, say the authors. However, cost was the main motive behind the recent high profile switching of two other drugs - omeprazole for stomach ulcers in Sweden and the antihistamine loratadine in the US.
The number of drugs being switched from prescription to over the counter availability is likely to continue to rise, and healthcare funders are likely to support manufacturers' applications to switch some drugs in an effort to curb the growth of prescription drugs, they say.
For patients, the trend towards more switches will take self care to a new level, focused increasingly on chronic prevention of serious illnesses, they conclude.