(in prescriptions) if necessary.
Origin of s.o.s.
From the Latin word sī opus sit
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
si opus sit (if needed)
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.