The claim that the blue lotus was used as a ritual intoxicant is repeated with great confidence, sold as a product on that basis, and remains unproven.
The case for it is iconographic and was argued most fully by William Emboden. Banquet scenes show the flower being inhaled with a persistence that seems more than decorative; some figures in those scenes appear to be vomiting or in altered states; the flower is associated with wine and with the drinking festivals of Hathor; and comparable water lily imagery appears in Maya art in contexts that also suggest ritual use. Emboden proposed the two traditions be read together.
The case against is pharmacological. The compounds most often named, apomorphine and nuciferine, are present in small amounts, apomorphine is a strong emetic and dopamine agonist with unpleasant effects rather than pleasant ones, and no study has demonstrated a psychoactive dose achievable from a quantity of flowers a person would plausibly consume or smell. Extraction into wine has been proposed and is not established.
A middle reading is available and probably closest to the evidence: the flower was overwhelmingly a symbol and a scent, its meaning fully explained by the sunrise imagery and its perfume, and any physiological effect was mild and secondary. Iconography shows what a thing meant, not what it did, and this atlas records the psychoactivity as contested rather than asserting either way.