This invention relates to pharmaceutical water, which comprises from 99.760 to 99.999% of light isotopologue .sup.1H.sub.2 .sup.16O and up to 100% of residual isotopologues .sup.1H.sub.2 .sup.17O, .sup.1H.sub.2 .sup.18O, .sup.1H.sup.2H.sup.16O, .sup.1H.sup.2H.sup.17O, .sup.1H.sub.2H .sup.18O, .sup.2H.sub.2 .sup.16O, .sup.2H.sub.2 .sup.17O, and .sup.2H.sub.2 .sup.18O, for the production of finished product, intermediate reagent preparation, and analytical processes in pharmaceutical industry. Further, the invention relates to pharmaceutical compositions comprising a biologically active agent and said pharmaceutical water, wherein said agent is selected from the group consisting of drugs, physiologically active peptides, physiologically active proteins, and nucleic acids. Further, the invention relates to method of administering a biologically active agent to a mammal in need thereof, which method comprises a step of administering to said mammal said therapeutic composition.