WordNet records no synonym and no antonym for detoxification. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a treatment for addiction to drugs or alcohol intended to remove the physiological effects of the addictive substances
treatment for poisoning by neutralizing the toxic properties (normally a function of the liver)
Synonyms, antonyms and the broader and narrower relations for detoxification come from Princeton University’s WordNet. Full sources and licences.