Nausea suppression

Nausea suppression is a reduction or elimination of the sensation of nausea during a psychoactive experience.

As a drug effect it is acute and dose-proportional, fading as the substance wears off. It ranges from a mild settling of gastric unease to near-complete abolition of active nausea, and can offer meaningful relief when nausea arises as a coinciding effect within the same session.

Nausea suppression is an uncommon effect relative to the broader range of reported somatic changes. It is most commonly induced at moderate to high doses under dissociatives such as 3-MeO-PCE, 3-MeO-PCP, and memantine, and under depressants such as lorazepam and promethazine. It also appears under cannabinoids such as cannabis and under antidepressants such as mirtazapine.

Nausea suppression is felt as a quieting of the gut: the roiling upward pressure of nausea eases and the urge to vomit recedes, leaving an unusual stillness in the abdomen.

It commonly comes with a broader reduction in body-awareness — tension around the diaphragm dissolves, salivation normalizes, and hypersensitivity to smell or motion subsides. Unlike most aversive sensations, it tends not to draw attention to itself; it is noticed as an absence rather than a presence. At higher doses, particularly under dissociatives, the broad blunting of interoception makes discomfort of any kind difficult to register.

Nausea suppression arises through different pathways depending on the drug class:

• Dissociatives — blunt interoceptive processing via NMDA receptor antagonism, attenuating nausea signals from the gut and vestibular system.
• Depressants — reduce central nervous system activity broadly; promethazine carries additional histamine H1 antagonism with direct antiemetic action.
• Cannabinoids — act on CB1 receptors in the dorsal vagal complex, suppressing the emetic reflex.
• Antidepressants — mirtazapine antagonizes H1 and 5-HT3 receptors, both implicated in nausea signaling.

How much each pathway contributes in a given case is not fully understood.

Who experiences it, and how strongly, varies widely. Higher doses raise both likelihood and depth. It appears most readily in people who already experience nausea within a session — underlying physiology matters more here than set and setting — and is most noticeable in those with prior sensitivity to motion sickness or gastrointestinal disturbance.

Expectation plays a smaller role than for experiential effects; nausea suppression tends to be noticed only after the fact. People without baseline nausea within a session may not register it at all.