Inhalation

Inhalation is the delivery of a substance to the lungs by breathing in smoke, vapor, or aerosol, where it is absorbed rapidly across the large surface of the airways.

The lungs offer fast entry into the bloodstream and avoid first-pass metabolism, so inhaled compounds typically act within minutes and reach higher peak concentrations than swallowed ones, but their effects also fade sooner. The route includes smoking dried flower, vaporizing flower or concentrates, and using pre-filled vape cartridges. Combustion produces tar and carbon monoxide; vaporization avoids combustion but can still generate irritants depending on temperature and formulation.

Inhaled hemp flower and CBD vape products exist, but inhalation raises safety considerations that oral and topical routes do not, including airway irritation and the risk of contaminated or adulterated cartridges. The U.S. Food and Drug Administration and the CDC have investigated lung injuries linked to vaping products, particularly those containing vitamin E acetate. Inhaled cannabinoids are not interchangeable with oral ones in terms of onset, exposure, or safety, and research on inhaled CBD specifically is limited.