Yan Hu Suo (Corydalis yanhusuo) is a small perennial herb native to China and Siberia whose rhizome has been a cornerstone of Traditional Chinese Medicine for over 1,000 years. It is officially listed in the Chinese Pharmacopoeia and is one of the most widely used botanical analgesics in East Asian medicine. The herb contains more than 20 isoquinoline alkaloids, with L-tetrahydropalmatine (L-THP) identified as the principal pharmacologically active compound responsible for its pain-modulating and sedative properties.

L-THP, the primary active alkaloid, exerts its analgesic and anxiolytic effects primarily through dopamine receptor antagonism (D1 and D2 receptors) and partial agonism at GABA-A receptors, mechanisms distinct from opioid pathways. This dual action modulates dopaminergic pain-signaling circuits and produces mild sedation without the dependency profile of opioid analgesics. Additional alkaloids such as dehydrocorydaline and protopine contribute anti-inflammatory and antispasmodic effects, further broadening the herb's analgesic profile.

Traditional use involves decocting the dried rhizome (3–9 g per day in formula). Modern products include standardized capsules and tablets (often 200–400 mg extract per dose), powdered rhizome, and isolated L-THP supplements. Standardized extracts calibrated to a known L-THP percentage provide the most reproducible dosing. TCM formulas frequently combine Yan Hu Suo with other herbs such as Bai Shao (white peony root) for dysmenorrhea.

• Dysmenorrhea (menstrual pain)
• Chronic musculoskeletal pain
• Anxiety
• Sleep disturbance/insomnia
• Visceral/abdominal pain

• Recurrence of menstrual pain episodes (supported by repeated-cycle use data in dysmenorrhea trials, though evidence quality is moderate)

• No direct dietary food source — L-THP and the isoquinoline alkaloids of Corydalis yanhusuo are not meaningfully present in common foods; supplementation or the prepared rhizome is required to obtain therapeutic concentrations.

• Sedation and drowsiness (most common, dose-dependent)
• Dizziness or lightheadedness
• Nausea or mild gastrointestinal upset
• Dry mouth
• Rare: hepatotoxicity with prolonged high-dose use
• Potential extrapyramidal effects with very high doses or long-term use (due to dopamine antagonism)
• Contraindicated in pregnancy (potential uterotonic activity)

• Recommended daily: Traditional decoction: 3–9 g dried rhizome per day. Standardized extract (capsule/tablet): 200–400 mg standardized extract per dose, 1–3 times daily, depending on L-THP content specification. Isolated L-THP products: typically 40–100 mg L-THP per dose. Always follow manufacturer specifications for the specific extract's alkaloid standardization.
• Best time of day: For pain management: take at the onset of pain or 30–60 minutes before anticipated pain triggers (e.g., before menstruation begins). For sleep support: 30–60 minutes before bedtime. Avoid daytime dosing if sedation is a concern.
• With or without food: Taking with food reduces risk of nausea and gastrointestinal discomfort; food does not appear to substantially impair absorption of the alkaloids based on traditional use patterns.
• Time to effect: Acute analgesic or sedative effects: 30–90 minutes post-dose. Sustained benefits for chronic pain or anxiety: 1–4 weeks of consistent use.
• How long to take it: Short-to-medium-term use (4–12 weeks) is best supported by available safety data. For menstrual pain, cyclic use during the premenstrual and menstrual phase is appropriate. Prolonged continuous high-dose use should include periodic liver function monitoring. A 2–4 week break after every 8–12 weeks of use is a prudent precaution given the limited long-term safety data.