Traditional abbreviation for the Latin omni bihorio, once every two hours, a unit of frequency sometimes used in medical prescriptions. The abbreviation alt. h. (alternis horis, every other hour) is equivalent
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}