(in prescriptions) as much as is sufficient; enough.
Origin of q.s.1
From the Latin word quantum sufficit
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
quantum satis (as much as is enough)
quantum sufficiat (as much as shall suffice)
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.