q.d.s. means quater die sumendus - four times a day in Prescription
Similar to q.d.s.
a.m. - ante meridiem - morning, before noon A.T.C. - around the clock a.u. - auris utraque - both ears aa - ana - of each ad - ad - up to ad lib. - ad libitum - use as much as one desires; freely admov. - admove - apply