From Longman Dictionary of Contemporary Englishover the counterover the counterMDdrugs, medicines etc that are bought over the counter are ones that you can buy in a shop without a prescription from a doctor → counter
Examples from the Corpus
over the counter• You feel you have to cough, and you spew the liquid all over the counter and sink.• Yeast remedies are available over the counter, and a physician can prescribe antibiotics for chlamydia, gonorrhea, and others.• Melatonin, available over the counter, is a hormone produced inside the brain by the pineal gland.• Something you could buy over the counter at a supermarket.• So why are they different when met over the counter in a social security office or a housing department?• You get them from the hospital or your doctor, not over the counter.• A freshly painted sign over the counter put closing time at nine-thirty; the clock next to it read nine-twenty-five.• Hon. Members can buy them over the counter in a chemist's shop.over-the-counterˌover-the-ˈcounter adjective [only before noun] 1 MDover-the-counter drugs can be obtained without a prescription (=a written order) from a doctor2 American EnglishBFS (abbreviation OTC) over-the-counter business shares are ones that do not appear on an official stock exchange listExamples from the Corpus
over-the-counter• Obvious examples include caffeine and ephedrine, the latter being readily available to the public in over-the-counter cold remedies.• We really only knew him through childhood over-the-counter dealings smiling, ever-patient, avuncular.• As yet there is no formal stock exchange, although a handful of securities are traded on the over-the-counter market.• Avoid over-the-counter medication containing benzoyl peroxide and alcohol - it dehydrates the area surrounding the spot.• Do not spend your life taking over-the-counter medication for the slightest ache or pain.• To combat chest congestion, Angol took an over-the-counter medication which contained a substance on the Olympic banned list.• If you've got a cold or sore throat, they can advise which over-the-counter medicines to take.• SmithKline could also benefit from Beecham's experience in selling over-the-counter medicines. 