NutriStack
Alcohol and Promethazine, a caution.
Alcohol can add to promethazine's sedating, anticholinergic, and coordination-impairing effects. Human studies show promethazine impairs psychomotor performance, and ethanol produces overlapping deficits in performance monitoring and reaction tasks. The combination is especially unsafe with opioids, sleep medicines, respiratory disease, or fall risk.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Substances
- Alcohol and Promethazine
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Alcohol can add to promethazine's sedating, anticholinergic, and coordination-impairing effects. Human studies show promethazine impairs psychomotor performance, and ethanol produces overlapping deficits in performance monitoring and reaction tasks. The combination is especially unsafe with opioids, sleep medicines, respiratory disease, or fall risk.
Mechanism. Promethazine blocks central H1 receptors and has antimuscarinic and antidopaminergic activity, producing sedation and slowed psychomotor performance. Alcohol adds CNS depression and worsens judgment and coordination through GABAergic and glutamatergic effects.
Recommendation. Avoid alcohol while taking promethazine for nausea, allergy, cough, or sleep. Do not drive or combine it with other sedatives if alcohol was used. Get urgent care for severe confusion, fainting, shallow breathing, or inability to wake.
Sources (2)
- Acons K, Chan LS, Drummond G, Tiplady B. Effects of ethanol and promethazine on awareness of errors and judgements of performance. J Psychopharmacol. 2006;20(5):661-669. PMID 16401655
- Kamei H, Isaji A, Noda Y, et al. Effects of single therapeutic doses of promethazine, fexofenadine and olopatadine on psychomotor function and histamine-induced wheal- and flare-responses: a randomized double-blind, placebo-controlled study in healthy volunteers. Arch Dermatol Res. 2012;304(4):263-272. PMID 22130869
Stack Score
How this pair moves the number.
Effect on the composite score
If both Alcohol and Promethazine are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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