Pharmacology · Class
Medical gases !
Gases given as medicines: oxygen corrects hypoxaemia and nitrous oxide gives analgesia and supports anaesthesia.
Updated 2026-11-01
What they are
Pharmaceutical-grade gases supplied in cylinders, hospital pipelines or concentrators: oxygen, nitrous oxide, medical air and, for special uses, inhaled nitric oxide and heliox. Oxygen is an essential medicine: it is prescribed, adjusted to a saturation target and has adverse effects.
Mechanism of action
Inspired oxygen raises the alveolar and arterial oxygen partial pressure and haemoglobin saturation; haemoglobin carries it to the tissues, where cytochrome c oxidase uses it to make energy. Under pressure (hyperbaric chamber) much more oxygen also dissolves in plasma and carbon monoxide is cleared faster.
Target: Haemoglobin (transport) and cytochrome c oxidase (cellular use)
Drugs in this class
Others in the class
- Medical air
- Inhaled nitric oxide
- Heliox
Test yourself
Think of the answer, then tap the question to see it.
Why is oxygen considered a medicine?
Because it has indications, a dose adjusted to a saturation target, adverse effects (lung toxicity, retinopathy of prematurity, atelectasis) and needs a prescription.
What physical risk makes smoking near a patient on oxygen forbidden?
Oxygen supports combustion: a spark or flame can start a fire and cause severe burns.
Which poisoning is treated with 100% or hyperbaric oxygen?
Carbon monoxide poisoning, because oxygen speeds the release of CO from haemoglobin.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 24 (McGraw Hill, 2023); Oxygen Therapy | Hyperbaric Oxygen Therapy | MedlinePlus (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.