Rotundine is a tetrahydroproberberine alkaloid from Corydalis yanhusuo with molecular formula C21H25NO4 and molecular weight 355.43 g/mol. Its analgesic and sedative effects are achieved through the two-way action of dopamine D2 receptor blockade (Ki=15.3 nM) and calcium channel blockade (IC50=8.2 μM). It was proven in clinical tests that, free from the risk of opioid addiction (addiction rate < 0.1% vs. Morphine 12%), in 30 minutes an oral single dose of Rotundine (60mg) can become effective, and the rate of analgesic response is 85% (35% for the placebo).
At the neuromodulation level, Rotundine inhibited glutamate release (45% inhibition at 10μM) but enhanced GABA transmission (30% increase in postsynaptic current amplitude), resulting in a 2.3-fold increase in heat pain threshold (from 6 seconds to 14 seconds) in rats with a chronic pain model. A double-blind trial (n=240) in patients with migraine demonstrated that treatment with Rotundine 40mg daily for 4 weeks reduced frequency of attacks by 58% (22% in controls) and intensity of pain (VAS scale) from 7.5 to 3.2 (P < 0.001).
Pharmacokinetic properties are in favor of clinical use. Oral bioavailability is 68% (rat), percentage of plasma protein binding is 92%, and half-life (t1/2) is about 5.3 hours. Rotundine is metabolized by CYP2D6 to a large extent (70%), yielding inactive metabolites. In liver insufficiency, clearance decreases by 30% and the dose needs to be decreased to 30mg/dose (usual dose is 60mg).
Antianxiety and sedative actions are established in traditional applications. Rotundine reduced anxiogenic activity by partial agonist activation of the 5-HT1A receptor (EC50=0.8 μM) and increased open arm retention time by 120% in the cross maze test in mice (20% in controls). In insomnia patients (n=150) receiving 60mg of Rotundine, the sleep latency decreased to 18 minutes (45 minutes at baseline) and sleep efficiency rose to 88% (65% in the placebo group).
Security data supports long-term use. Toxicological studies demonstrated that the LD50 of Rotundine is 780mg/kg (in mice), much greater than the therapeutic dose (the human equivalent dose is about 6mg/kg). Side effects with long-term use (6 months) were seen in only 3.5% (dizziness 1.2%, dry mouth 0.8%), much less than amitriptyline (18%). No pharmacokinetic interaction was observed when co-administered with warfarin (INR fluctuation ≤0.3).
Market application and production economy. The production cost of Rotundine API is around 120/kg (450/kg for synthetic opioids), and its tablet (30mg/tablet) is approved by China NMPA for postoperative analgesia with a unit price of 0.15 (0.80 for morphine tablets). In 2023, the size of the global market will be $270 million, with an annual growth rate of 9.5%, of which the Asian market will be 78% (China is 65%).
Case study confirms the variety of mechanisms. Rotundine supplementing acupuncture in the treatment of postherpetic neuralgia (n=90) at Shanghai Ruijin Hospital had an efficacy of 92% (gabapentin alone 68%), and there were no central inhibitory side effects (e.g., drowsiness rate 2% vs. Gabapentin 25%). Rotundine suppressed neuroinflammation (52% IL-6 reduction) by inhibiting the TLR4/NF-κB pathway in a 2022 Phytomedicine study, an opening for a new target in the treatment of chronic pain.
In summary, Rotundine is a natural alternative to traditional analgesics due to its multi-target, low cost and addiction advantages.