In the
U.S.,
drugs are either over the counter or
scheduled. Scheduled drugs require a
prescription (British:
script) from a
doctor to purchase. Over the coutner drugs can be purchased freely and include non-
opiate painkillers,
antihistamines,
decongestants,
caffeine,
antacids,
antibiotic ointments, and
laxatives, among others. The distinction is made at the level of individual chemicals, though, so some drugs in any of the above categories may still require a doctor's okay (presumably because they are not sufficiently tested, or because their
side effects are severe enough to require
medical oversight).
Scheduled drugs include oral antibiotics, antidepressants, opiates, and many others. Schedules range from V (loosely controlled) to I (cannot be prescribed by any doctor; usable only in limited experimental contexts; supposedly highly addictive and life-threatening to use). If you wonder why I'm qualifying these terms so heavily, note that
marijuana is schedule I.