Ph. Int. (International Pharmacopoeia)

WHO gives its fundamental aim as global harmonisation of quality specifications for selected pharmaceutical products, excipients and dosage forms. The first volume was published in 1951; from 1975 it has focused on medicines in the WHO Model List of Essential Medicines. Announcing the 11th edition in 2023, WHO said the Ph. Int. focuses on monographs of particular relevance to low- and middle-income countries, which may not have sufficient resources to develop national pharmacopoeias.

The 13th edition, published in 2025, revised the monograph Medicinal oxygen, which defines medicinal oxygen as Oxygen 93%, Oxygen 98% or Oxygen 99.5%:

• Oxygen 93%: 90.0% to 96.0% (V/V) of O2, produced from ambient air by pressure swing adsorption (PSA) or vacuum swing adsorption (VSA).
• Oxygen 98%: not less than 96.0% of O2, from a two-stage adsorption plant.
• Oxygen 99.5%: at least 99.5% of O2, produced from ambient air by cryogenic distillation.

Mixtures of these qualities may be used clinically, but the monograph requirements do not apply to any mixture, nor to oxygen from portable concentrators for home care or bedside use. The limits for each quality are on the Medicinal oxygen standard page.