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Herbsmith Rx Er Xian San is a Chinese herbal formula recommended by holistic veterinarians to warm the kidney yang, tonify the kidney essence, and drain deficiency fire within TCVM in dogs, cats, and horses. Also known as Curculigo and Epimedium Powder and Two Immortals, this six-herb formula addresses the combined kidney yin and yang vacuity pattern with ascending deficiency fire. Its traditional strategy combines warming kidney yang, supporting yin and essence, draining deficiency fire, and nourishing blood. Er Xian Tang has a history of use in human climacteric care; veterinary selection depends on the animal's own TCVM pattern rather than assuming a direct equivalent of human menopause. The name Er Xian (Two Immortals) refers to the principal yang-warming herbs Xian Mao (curculigo, 23%) and Yin Yang Huo (epimedium, 23%). Ba Ji Tian (morinda root, 14%) adds gentler yang tonification; Huang Bai (phellodendron bark, 13%) and Zhi Mu (anemarrhena, 13%) provide the fire-draining and yin-supporting complement; and Dang Gui (Chinese angelica root, 14%) nourishes and moves blood. The mixed pattern may include cold sensitivity alongside heat signs, lower back and hindlimb weakness, reduced stamina, and restlessness associated with deficiency fire. Tongue and pulse findings may include a red or pale-red tongue with scanty coating and a deep, thin, or slightly rapid pulse. These signs require veterinary diagnosis and pattern differentiation. Available as a concentrated powder mixed into food; cats and dogs use the Canine Blend, while horses use the Equine/Horse Blend. Dosing varies by species and body weight, and your authorizing veterinarian will provide specific guidance.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
What It Supports
- Kidney yang warming through Xian Mao and Yin Yang Huo: In TCVM, Xian Mao (curculigo rhizome, 23%) and Yin Yang Huo (epimedium herb, 23%) warm kidney yang and support the life gate fire (ming men). Xian Mao contributes a strongly warming, cold-dampness-dispersing action. Yin Yang Huo complements this with sinew and bone support and wind-cold-dampness dispersal. Together, they provide the warming component for lower back and hindlimb weakness within the combined deficiency pattern. Their warming character is a reason for careful pattern selection and monitoring, not an indication for use in every aging animal.
- Supplementary kidney yang support through Ba Ji Tian: Ba Ji Tian (morinda root, 14%) tonifies kidney yang, strengthens sinews and bones, and dispels wind-cold-dampness. Its traditionally gentler, more moistening character complements Xian Mao and Yin Yang Huo in a formula intended to address yang weakness alongside yin insufficiency.
- Deficiency fire clearing and yin support through Huang Bai and Zhi Mu: Huang Bai (phellodendron bark, 13%) and Zhi Mu (anemarrhena, 13%) form the cooling complement to the warming herbs. Huang Bai drains lower-jiao fire, while Zhi Mu clears heat, nourishes yin, and generates fluids. Their role is to address the deficiency-heat component within the combined yin-yang pattern; the pairing does not guarantee that the warming herbs cannot aggravate heat or dryness in an individual animal.
- Blood nourishment through Dang Gui: Dang Gui (Chinese angelica root, 14%) tonifies and invigorates blood, nourishes liver blood, and traditionally regulates the Chong and Ren vessels. In the formula strategy, blood nourishment connects the warming and yin-supporting groups, while gentle movement accompanies tonification. Traditional vessel language is not evidence of a guaranteed hormonal or reproductive outcome.
TCVM Principles
- Primary action: Warm kidney yang while supporting yin and addressing deficiency fire in a confirmed combined kidney yin-yang vacuity pattern. Xian Mao, Yin Yang Huo, and Ba Ji Tian provide the warming group; Huang Bai and Zhi Mu provide the fire-draining and yin-supporting group; Dang Gui nourishes and moves blood.
- Formula framework: The Two Immortals strategy is related to Er Xian Tang, with warming and cooling ingredients selected for a mixed deficiency presentation. It is not interchangeable with a purely warming yang formula or a purely yin-nourishing and fire-clearing formula.
- Chong and Ren vessel context: Traditional interpretation links kidney essence and blood nourishment with the Chong and Ren vessels, which are discussed in relation to constitutional and reproductive rhythms. Your veterinarian assesses the animal's actual clinical condition and pattern rather than inferring an endocrine diagnosis from these concepts.
- Contraindicated patterns: Not appropriate for pure kidney yin vacuity with fire without accompanying yang vacuity, pure kidney yang vacuity with a cold pattern and no deficiency fire, or excess/repletion heat. TCVM kidney vacuity is a pattern description, not by itself a diagnosis of kidney disease.
- Safety and monitoring: Xian Mao requires particular attention to dose, preparation, and gastrointestinal tolerance. Veterinary medication review and periodic reassessment are required. If gastrointestinal irritation or another suspected adverse reaction occurs, stop administration and contact your veterinarian.
Available Forms
- Powder - Canine Blend (for dogs and cats): Available in 75 g, 150 g, 500 g, 900 g, and 1200 g sizes; mix into food at the recommended dose for your pet's weight. Cats and dogs both use this blend.
- Powder - Equine/Horse Blend (for horses only): Available in 150 g, 500 g, 900 g, and 1200 g sizes; mix into grain at the recommended dose for your horse.
Suggested Use
- Canine Blend Powder - Dogs under 30 lbs: ½ tsp twice daily, or as directed by your veterinarian.
- Canine Blend Powder - Dogs 30-80 lbs: 1 tsp twice daily, or as directed by your veterinarian.
- Canine Blend Powder - Dogs 80-120 lbs: 1½ tsp twice daily, or as directed by your veterinarian.
- Canine Blend Powder - Dogs over 120 lbs: 2 tsp twice daily, or as directed by your veterinarian.
- Canine Blend Powder - Cats: ¼ tsp twice daily, or as directed by your veterinarian.
- Equine/Horse Blend - 1,000 lb horse, initial dose: Two tablespoons twice daily, or as directed by your veterinarian. Continue the initial schedule for 20 days, or as directed by your veterinarian.
- Equine/Horse Blend - 1,000 lb horse, maintenance dose: After the initial period, give two tablespoons once daily in grain, or as directed by your veterinarian.
If the horse initially refuses, start with a small amount mixed into grain and gradually increase until accustomed to the taste, or as directed by your veterinarian. Most horses will readily accept the herbs in their grain. Confirm the dog dose at the overlapping 80 lb boundary with your authorizing veterinarian. Veterinary authorization and medication review are required. Use only for the confirmed mixed yin-yang vacuity pattern with deficiency fire, not the contraindicated patterns described above. Continue for the prescribed duration, or as directed by your veterinarian. Stop administration and contact your veterinarian if gastrointestinal irritation or another suspected adverse reaction occurs.
Ingredients
Active Ingredients: Xian Mao (Rhizoma Curculiginis Orchioidis) - Curculigo rhizome, 23%; Yin Yang Huo (Herba Epimedii) - Epimedium herb, 23%; Ba Ji Tian (Radix Morindae Officinalis) - Morinda root, 14%; Dang Gui (Radix Angelicae Sinensis) - Chinese angelica root, 14%; Huang Bai (Cortex Phellodendri) - Phellodendron bark, 13%; Zhi Mu (Radix Anemarrhenae Asphodeloidis) - Anemarrhena, 13%.
Inactive Ingredient: Flaxseed.
Ingredient information: Names and percentages retain the existing listing composition. Exact botanical species, processing details, and constituent concentrations have not been independently verified against a current manufacturer label. Confirm the selected blend's current label information with the manufacturer or your authorizing veterinarian.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
Active Ingredient TCVM Actions
Er Xian San combines three complementary functional groups: kidney yang warming (Xian Mao, Yin Yang Huo, Ba Ji Tian), deficiency fire clearing and yin support (Huang Bai, Zhi Mu), and blood nourishment and movement (Dang Gui):
- Xian Mao (Rhizoma Curculiginis Orchioidis) - Curculigo Rhizome / Golden Eye Grass Rhizome: Traditionally strongly warms and tonifies kidney yang, disperses cold and dampness, and strengthens sinews and bones. Its hot, acrid character provides the most concentrated warming role in the formula. This ingredient requires particular veterinary oversight, including confirmation of preparation and monitoring for gastrointestinal irritation, especially in animals with digestive sensitivity. Do not use this formula for yin vacuity fire without the accompanying yang vacuity pattern. Specific constituent classifications and finished-product toxicity thresholds are not established by the existing listing information.
- Yin Yang Huo (Herba Epimedii) - Epimedium Herb / Horny Goat Weed / Barrenwort: Traditionally warms kidney yang and life gate fire, strengthens sinews and bones, and dispels wind-cold-dampness. The existing copy identifies icariin and related flavonoids as constituents of interest; constituent research on vascular, phosphodiesterase, bone-related, or hormonal pathways does not establish equivalent clinical effects or outcomes for this finished formula in veterinary patients. Review use with cardiac, pulmonary hypertension, anticoagulant, or hormonal medications and in animals with hormone-sensitive conditions with your veterinarian.
- Ba Ji Tian (Radix Morindae Officinalis) - Morinda Root / Indian Mulberry Root: Tonifies kidney yang and essence, strengthens sinews and bones, and dispels wind-cold-dampness. Its traditionally gentler, more moistening character complements Xian Mao and Yin Yang Huo within the mixed yin-yang deficiency strategy. It does not remove the need to monitor for heat, dryness, or a changing pattern.
- Huang Bai (Cortex Phellodendri) - Phellodendron Bark: Traditionally drains kidney and lower-jiao fire and clears damp-heat. In Er Xian San it provides a fire-clearing counterbalance within the mixed deficiency strategy rather than a purely excess-heat formula. The existing copy identifies berberine-related drug-metabolism and transport concerns; prescription medications require veterinary review. The available ingredient name does not establish a single botanical species or a measured berberine amount.
- Zhi Mu (Radix Anemarrhenae Asphodeloidis) - Anemarrhena: Nourishes yin, generates fluids, drains fire, and clears heat from the lung, stomach, and kidney channels. Its pairing with Huang Bai is traditionally associated with yin vacuity and deficiency fire. Within Er Xian San, its fluid-supporting and cooling roles complement the warming group; the animal's ongoing pattern and tolerance still require reassessment.
- Dang Gui (Radix Angelicae Sinensis) - Chinese Angelica Root / Dong Quai: Tonifies and invigorates blood, nourishes liver blood, traditionally regulates the Chong and Ren vessels, and moistens the intestines. Its nourishment and movement connect the warming and cooling groups within the formula strategy. Review concurrent anticoagulant, antiplatelet, hormonal, or reproductive medications with the veterinarian rather than assuming the herbal combination is free of additive effects.
Potential Drug Interactions
Er Xian San contains strongly warming Xian Mao, yang-tonifying Yin Yang Huo and Ba Ji Tian, Blood-nourishing and Blood-moving Dang Gui, and cooling Huang Bai and Zhi Mu. Ingredients with potential effects on circulation, hormonal pathways, medication metabolism, and gastrointestinal tolerance warrant review alongside prescriptions. Pets taking prescription medications should use this formula under veterinary supervision because herb-drug interaction research in dogs and cats is limited. Horses taking prescription medications also require veterinary review. Use only for confirmed kidney yin-yang dual vacuity with deficiency fire, not pure yin vacuity fire, pure yang vacuity cold, or excess heat.
Medication categories warranting extra caution include cardiac and pulmonary hypertension medications, including sildenafil or tadalafil, anticoagulant or antiplatelet medications, hormonal or reproductive medications, immunosuppressive medications including cyclosporine and tacrolimus, digoxin, statins, other medications with narrow therapeutic ranges processed by liver enzymes or drug-transport pathways, and multiple concurrent prescriptions. Animals with gastrointestinal sensitivity also require review. Stop administration and contact your veterinarian if gastrointestinal irritation or another suspected adverse reaction occurs. Your authorizing veterinarian can determine appropriateness based on your animal's condition, current medications, and laboratory results, together with tongue, pulse, and assessment of the mixed hot-cold presentation.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
Frequently Asked Questions
What is Er Xian San used for in TCVM?
Er Xian San is selected for combined kidney yin and yang vacuity with deficiency fire. This mixed pattern may include cold sensitivity, lower back and hindlimb weakness, fatigue, and reduced stamina alongside heat-related restlessness, thirst, or disturbed rest. A red or pale-red tongue with scanty coating and a deep, thin, or slightly rapid pulse may contribute to the assessment. Your authorizing veterinarian distinguishes this from pure yang vacuity with cold, pure yin vacuity with fire, and other causes of weakness or behavioral change. A TCVM kidney pattern does not by itself establish kidney disease or an endocrine diagnosis.
How is Er Xian San administered to dogs, cats, and horses?
Mix the powder into food or grain. Dogs and cats use the Canine Blend. For dogs under 30 lbs, give ½ tsp twice daily, or as directed by your veterinarian. For dogs 30-80 lbs, give 1 tsp twice daily, or as directed by your veterinarian. For dogs 80-120 lbs, give 1½ tsp twice daily, or as directed by your veterinarian. For dogs over 120 lbs, give 2 tsp twice daily, or as directed by your veterinarian. For cats, give ¼ tsp twice daily, or as directed by your veterinarian. Confirm the dog dose at the overlapping 80 lb boundary with your authorizing veterinarian.
Horses use the Equine/Horse Blend. For a 1,000 lb horse, give two tablespoons twice daily, or as directed by your veterinarian. Continue the initial schedule for 20 days, or as directed by your veterinarian. Then give two tablespoons once daily in grain, or as directed by your veterinarian. If the horse initially refuses, start with a small amount mixed into grain and gradually increase until accustomed to the taste, or as directed by your veterinarian. Review all current medications before use. Continue only for the prescribed duration, or as directed by your veterinarian. Stop administration and contact your veterinarian if gastrointestinal irritation or another suspected adverse reaction occurs.
How is progress assessed with Er Xian San?
Your veterinarian will assess stamina, lower back and hindlimb function, temperature-related signs, rest and behavior, tongue, and pulse alongside the underlying clinical diagnosis and any appropriate laboratory testing. Response timing varies with the animal's condition, degree of constitutional weakness, and concurrent care; a fixed improvement or restoration timeline cannot be promised. Continue for the prescribed duration, or as directed by your veterinarian. Regular reassessment determines whether the mixed yin-yang pattern remains present and whether the formula or care plan needs adjustment.
Why does Er Xian San contain both warming and cooling herbs?
The traditional strategy addresses two coexisting aspects of the mixed pattern: insufficient kidney yang warmth and deficiency heat associated with yin insufficiency. Xian Mao, Yin Yang Huo, and Ba Ji Tian supply the warming group; Huang Bai and Zhi Mu supply fire clearing and yin support; Dang Gui adds blood nourishment and movement. This differs from treating excess heat with a purely cooling approach or pure cold deficiency with a purely warming approach. The combined design does not guarantee that warming cannot worsen heat or cooling cannot be inappropriate. Your authorizing veterinarian's pattern assessment and follow-up determine whether this balance suits your animal.
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