SI units in drug therapeutics.

LE SYSTEME INTERNATIONAL D'UNITES (International System of Units) (SI) has been in existence since 1954. The World Health Organization recommended its adoption in 1977. In the U.S., the Metric Conversion Act passed by Congress in 1975endorsed the use of SI. I Although much of the medical world has changed to this coherent system of metric units, the U.S. has muddled along with the older conventional units, particularly in clinical chemistry and hematology. The major SI change in drug therapeutics is that drug concentrations in body fluids are reported in molar terms rather than mass units. In time, even drug doses may be expressed in molar quantities, a change further enlightening drug therapeutics.