Zeolite.  Hydrous silicate, used for ion or molecule trapping. An artificial zeolite is used in O₂ concentrators, to retain nitrogen from compressed air. Has also been added to soda lime to retain water and prevent drying out.

Zero, absolute.  The lowest possible temperature that can be attained: 0 kelvin (corresponds to −273.15°C).

Zero-order kinetics,  see Pharmacokinetics

Ziconotide acetate.  Synthetic form of a peptide derived from the venomous sea snail Conus magus, introduced in 2006 for the treatment of chronic pain. Acts as a neurone-specific N-type calcium channel blocking drug and thought to interrupt ascending pain pathways in the spinal cord.