I vaguely remember reading a novel with a similar setting to "The Giver", but the nothingness was delivered via injection rather than a daily pill. About all I can recall is that the hero is given the advice "leaves keep you dry from the rain" which he interprets correctly as instruction to place a few layers of cloth on his arm so the injection doesn't reach his skin. The story then has him going on a trek to try to find and destroy the master computer-ish thing which runs the pseudo-utopian society.
Ira Levin's novel, "This Perfect Day", is very similar to "The Giver". The population is controlled by a drug that is delivered regularly. A computer named UniComp keeps all humans in check.
I do not recall the part you mention about the hero being told "leaves keep you dry from the rain", but the hero "Chip", is taught how to reduce the drugs to experience feelings and such. The novel also has a journey by the hero to destroy the computer.