NutriStack
Diphenhydramine and Valerian Root, a caution.
Diphenhydramine can cause meaningful drowsiness, slowed reaction time, anticholinergic confusion, and driving impairment. Valerian root is commonly used as a sleep aid and has GABAergic pharmacology, even though controlled human data show inconsistent acute sedation. Combining them can increase next-day grogginess, falls, and impaired driving, especially in older adults or when alcohol, opioids, benzodiazepines, or other sleep aids are also used.
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
- Diphenhydramine and Valerian Root
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- Source citations
- 3 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Emerging evidence
Caution
What is happening. Diphenhydramine can cause meaningful drowsiness, slowed reaction time, anticholinergic confusion, and driving impairment. Valerian root is commonly used as a sleep aid and has GABAergic pharmacology, even though controlled human data show inconsistent acute sedation. Combining them can increase next-day grogginess, falls, and impaired driving, especially in older adults or when alcohol, opioids, benzodiazepines, or other sleep aids are also used.
Mechanism. Diphenhydramine blocks central H1 and muscarinic receptors, producing sedation and cognitive slowing. Valerian constituents, including valerenic acid, can modulate GABAergic signaling, creating a plausible additive CNS-depressant burden despite variable clinical sedative effects.
Recommendation. Avoid using valerian root to boost diphenhydramine for sleep unless your clinician specifically approves the combination. If both are used, take them only when you can sleep a full night and avoid driving or hazardous tasks the next morning if you feel slowed or foggy. Stop the combination if you develop confusion, severe dizziness, or unusually prolonged sedation.
Sources (3)
- Glass JR, Sproule BA, Herrmann N, Streiner D, Busto UE. Acute pharmacological effects of temazepam, diphenhydramine, and valerian in healthy elderly subjects. J Clin Psychopharmacol. 2003;23(3):260-268. PMID 12826988
- Weiler JM, Bloomfield JR, Woodworth GG, et al. Effects of fexofenadine, diphenhydramine, and alcohol on driving performance: a randomized, placebo-controlled trial in the Iowa driving simulator. Ann Intern Med. 2000;132(5):354-363. PMID 10691585
- Yuan CS, Mehendale S, Xiao Y, Aung HH, Xie JT, Ang-Lee MK. The gamma-aminobutyric acidergic effects of valerian and valerenic acid on rat brainstem neuronal activity. Anesth Analg. 2004;98(2):353-358. PMID 14742369
Stack Score
How this pair moves the number.
Effect on the composite score
If both Diphenhydramine and Valerian Root 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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