Valerian root interacts most significantly with sedative medications, alcohol, and certain drugs processed by a specific liver enzyme called CYP3A4. Because valerian works on the same brain receptors as many prescription sedatives, combining them can amplify drowsiness, confusion, and impaired coordination beyond what either substance would cause alone.
How Valerian Causes Interactions
Valerian’s active compounds, particularly valerenic acid and valerenol, bind directly to GABA-A receptors in the brain. These are the same receptors targeted by benzodiazepines, barbiturates, and general anesthetics. When valerian occupies these receptors, it enhances the brain’s main calming signal, producing sedation and reducing anxiety. This shared mechanism is why combining valerian with other drugs that act on GABA receptors creates the strongest and most predictable interactions.
Valerian also affects how your liver processes other drugs. Your liver uses a family of enzymes to break down medications, and one of the most important is CYP3A4, which handles roughly half of all prescription drugs on the market. Lab studies show valerian can inhibit CYP3A4 activity by 35 to 88%, which could slow the breakdown of other medications and cause them to build up in your bloodstream. That said, one small clinical trial in 12 healthy volunteers taking 1,000 mg of valerian daily for two weeks found no significant changes in CYP3A4 activity. The real-world impact likely depends on the dose and the specific valerian product.
Benzodiazepines and Barbiturates
This is the most clinically relevant category. Benzodiazepines like alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan), and triazolam (Halcion) all work on the same GABA-A receptors that valerian targets. Taking them together can produce additive sedation: deeper drowsiness, slowed reflexes, impaired judgment, and in serious cases, dangerously slowed breathing.
Barbiturates and other central nervous system depressants carry the same risk. The NIH specifically flags phenobarbital, morphine, and propofol as drugs that may interact with valerian through this shared sedative pathway. Valerian extracts have also been shown to interact synergistically with clonazepam in animal models, meaning the combined effect was greater than what you’d expect from simply adding the two together.
Seizure Medications
If you take anticonvulsants, valerian introduces a layered interaction. Patients who self-administer valerian alongside seizure medications may experience increased sedation, which is a concern for daily functioning. But the interaction goes beyond drowsiness. In zebrafish studies, valerian extracts markedly enhanced the anticonvulsant effects of both clonazepam and phenytoin. Ethanolic valerian extracts showed a direct interaction with phenytoin specifically. While an enhanced anticonvulsant effect might sound helpful, unpredictable changes in how well your seizure medication works can be dangerous, particularly if it leads to excessive sedation or altered drug levels.
Alcohol
Combining valerian with alcohol increases dizziness, drowsiness, confusion, and difficulty concentrating. You may also experience impaired motor coordination, thinking, and judgment. Because both substances depress the central nervous system through overlapping pathways, even moderate amounts of alcohol on top of a standard valerian dose can produce noticeably heavier sedation than either one alone.
Drugs Processed by CYP3A4
Because valerian can slow down CYP3A4 enzyme activity, it has the potential to raise blood levels of any medication that depends on this enzyme for breakdown. CYP3A4 processes a huge range of drugs, including many cholesterol-lowering statins (like simvastatin and atorvastatin), calcium channel blockers used for blood pressure, certain antifungal medications, some immunosuppressants, and various HIV medications. When this enzyme is inhibited, these drugs clear your body more slowly, which can intensify both their intended effects and their side effects.
The practical significance here is still debated. Lab studies consistently show inhibition, but the one clinical trial testing this in humans found no measurable change. The discrepancy may come down to dose, duration, and the specific valerian preparation used. Products vary widely in their concentration of active compounds. If you take a medication with a narrow margin between a therapeutic dose and a toxic dose, this interaction deserves more caution.
Other Sedative Herbs and Supplements
Valerian is often combined with other calming herbs like kava, hops, passionflower, or melatonin in sleep-aid blends. These combinations can stack sedative effects unpredictably. Passionflower, like valerian, enhances GABA receptor activity, and combining the two with a benzodiazepine could lead to severe adverse effects. One published case report described acute delirium in a patient exposed to St. John’s wort, valerian, and loperamide (an over-the-counter anti-diarrheal), though the exact mechanism remains unclear.
Liver Concerns With Herbal Combinations
Valerian has been linked to a small number of liver injury cases, though almost always when taken alongside other potentially liver-damaging herbs like skullcap, black cohosh, or chaparral. The LiverTox database rates valerian as a “probable rare cause” of clinically apparent liver injury. In the reported cases, patients typically developed fatigue followed by jaundice within one to three weeks of starting a multi-herb product. The liver injury pattern resembles acute hepatitis, with markedly elevated liver enzymes. Most cases resolved within 7 to 25 weeks after stopping the product, though some required treatment for prolonged symptoms.
If you already take a medication that stresses the liver, or if you’re combining valerian with other herbal supplements, the risk of liver injury is worth keeping in mind, even though it appears to be uncommon.
Anesthesia and Surgery
Because valerian acts on the same receptors as many anesthetic drugs, it can interfere with sedation during surgery in unpredictable ways. Both the American Society of Anesthesiologists and the American Association of Nurse Anesthetists recommend stopping all herbal medications, including valerian, one to two weeks before any elective surgical procedure. This washout period gives your body time to clear valerian’s active compounds so they don’t amplify the effects of anesthesia or complicate your recovery.