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Herbsmith Rx An Zhong San is a classical Chinese herbal formula recommended by holistic veterinarians to warm and strengthen the middle burner, regulate the qi, invigorate the blood, and address epigastric discomfort from spleen and stomach yang vacuity with cold, qi stagnation, and blood stasis in dogs, cats, and horses. Also known as Fennel and Galanga Formula and Calm the Middle, An Zhong San is a seven-herb middle burner warming and regulating formula that addresses the complex pattern of spleen and stomach yang vacuity with cold accumulation, qi stagnation, and blood stasis simultaneously. The formula's name references its primary action of calming and settling the middle jiao, and its common name highlights its two signature herbs: Xiao Hui Xiang (fennel) and Gao Liang Jiang (galanga), both of which warm the middle jiao and dispel cold from the stomach and spleen channels. An Zhong San addresses a multi-layered middle jiao pattern where spleen and stomach yang vacuity allows cold to accumulate in the middle jiao, obstructing the free flow of qi and blood and generating the characteristic epigastric discomfort, abdominal distention, sour regurgitation or nausea, and sharp cramping that arise from cold obstructing the middle jiao's qi and blood circulation. The formula's blood-activating herb (Yan Hu Suo) addresses the blood stasis component of the pattern, while Duan Mu Li (calcined oyster shell) calms the liver, absorbs stomach acid, and addresses the sour regurgitation that cold-and-qi-stagnation in the middle jiao generates. Well suited for dogs, cats, and horses presenting with the spleen-stomach yang vacuity cold pattern with qi stagnation and blood stasis, characterized by a pale or pale-purple tongue with a white moist coating reflecting cold and yang vacuity; epigastric or abdominal discomfort that worsens with cold and improves with warmth and pressure; sour regurgitation, nausea, or vomiting from cold-induced stomach qi rebellion; a feeling of fullness and distention in the chest and abdomen from qi stagnation; and a wiry-tight or wiry-slow pulse. Available as a concentrated powder mixed into food; dogs and cats 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
For Dogs (Canine Blend Powder):
For Cats (Canine Blend Powder): ¼ tsp twice daily, or as prescribed
For Horses (Equine/Horse Blend, 1,000 lb horse): Two tablespoons twice daily for 20 days, then two tablespoons once daily in grain. If the horse initially refuses, start with a small amount mixed into grain and gradually increase. Most horses will readily accept the herbs in their grain.
Active Ingredients: Rou Gui (Cinnamomi Cortex), Yan Hu Suo (Corydalis Rhizoma), Duan Mu Li (calcined Ostreae Concha), Xiao Hui Xiang (Foeniculi Fructus), Pao Jiang (Zingiberis Rhizoma preparata), Gao Liang Jiang (Alpiniae officinarum Rhizoma), Gan Cao (Glycyrrhizae Radix)
Inactive Ingredient: Flaxseed
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
An Zhong San is a seven-herb formula organized around three therapeutic strategies: middle jiao warming and cold dispelling (Rou Gui, Xiao Hui Xiang, Pao Jiang, Gao Liang Jiang), blood activating and qi moving (Yan Hu Suo), and liver calming with acid absorbing and formula harmonizing (Duan Mu Li, Gan Cao):
An Zhong San has a moderate drug interaction profile centered on two primary herbs. The main concern is Yan Hu Suo's tetrahydropalmatine and isoquinoline alkaloid content, which has dopaminergic and GABAergic activity; animals on sedatives (phenobarbital, benzodiazepines), monoamine oxidase inhibitors (MAOIs), or cardiovascular medications warrant veterinary review of interaction potential before initiating this formula, as combined sedative or cardiovascular effects are possible. The second concern is Rou Gui's coumarin content and anticoagulant effects, which warrant monitoring in animals on warfarin, heparin, aspirin, clopidogrel, or other anticoagulant or antiplatelet medications. Duan Mu Li's high mineral (calcium) content can affect the absorption of certain oral medications, including some antibiotics (tetracyclines, fluoroquinolones) and thyroid medications, where calcium binding reduces bioavailability; administration timing relative to these medications warrants veterinary guidance. Gan Cao's glycyrrhizin content warrants monitoring with corticosteroids and antihypertensive medications.
Medication categories warranting extra caution: sedatives and anxiolytics (Yan Hu Suo alkaloid GABAergic effects), MAOIs (Yan Hu Suo dopaminergic activity), cardiovascular medications (Yan Hu Suo alkaloid effects), anticoagulant and antiplatelet medications (Rou Gui coumarin effects), certain antibiotics and thyroid medications (Duan Mu Li calcium binding), corticosteroids (Gan Cao glycyrrhizin mineralocorticoid effects), and antihypertensive medications (Gan Cao fluid-retaining tendency). Because An Zhong San is a warming formula, it is contraindicated in animals with stomach heat or yin vacuity heat signs (red tongue, yellow coating, rapid pulse) where the warming herbs would aggravate the heat. Your authorizing veterinarian will determine appropriateness based on your animal's condition, current medications, tongue quality, pulse character, and clinical assessment of the middle jiao cold-stagnation pattern.
VETERINARY AUTHORIZATION REQUIRED: Submit Your Authorization Request or Request a TCVM Telemedicine Consultation
In Traditional Chinese Veterinary Medicine, An Zhong San is indicated for the spleen and stomach yang vacuity cold pattern with qi stagnation and blood stasis. The clinical presentation centers on epigastric or abdominal discomfort that worsens with cold and improves with warmth and gentle pressure, reflecting the cold-origin stagnation; sour regurgitation, nausea, or vomiting from cold-induced stomach qi rebellion; a feeling of fullness and distention in the chest and abdomen from qi stagnation; a pale or pale-purple tongue with a white moist coating reflecting cold and yang vacuity; and a wiry-tight or wiry-slow pulse. This formula is suited to the cold-stagnation pattern and is contraindicated in animals with signs of stomach heat or yin vacuity heat. Veterinary tongue and pulse examination is essential to differentiate the spleen-stomach cold pattern from stomach heat or liver fire patterns that require cooling rather than warming strategies.
Mix the powder into food or grain at the dose recommended for your animal's species and body weight. Dogs and cats use the Canine Blend; horses use the Equine/Horse Blend. All species receive the formula twice daily, with horses following the standard 20-day twice-daily loading protocol before transitioning to once-daily maintenance dosing. Because An Zhong San contains Yan Hu Suo with dopaminergic and GABAergic alkaloid activity and Rou Gui with anticoagulant effects, we recommend a veterinary review of all current medications before use, particularly for animals on sedatives, MAOIs, cardiovascular medications, or anticoagulants. This formula is warming and must not be used in animals with stomach heat or yin vacuity heat patterns; pattern confirmation by your authorizing veterinarian is important before initiating treatment.
As a formula addressing both an acute pattern of cold-induced qi and blood stagnation in the middle jiao and the underlying spleen-stomach yang vacuity, An Zhong San works on two timeframes. The cold-dispersing and qi-moving herbs (Gao Liang Jiang, Xiao Hui Xiang, Pao Jiang, Yan Hu Suo) may provide relatively early improvement in the acute middle jiao stagnation signs, with reduction in epigastric discomfort, nausea, and abdominal distention potentially seen within 1 to 2 weeks as the cold obstruction begins to clear. The deeper spleen and stomach yang tonification (Rou Gui providing the primary constitutional warming) requires sustained treatment to rebuild the spleen and stomach yang from the root level; meaningful improvement in the underlying tendency toward cold accumulation and qi stagnation typically requires 4 to 8 weeks of consistent use. Your authorizing veterinarian will monitor tongue, pulse, and digestive signs throughout.
An Zhong San may be appropriate for horses presenting with the spleen-stomach yang vacuity cold pattern with qi stagnation, which can manifest as cold-weather digestive discomfort, epigastric fullness and distention, nausea or reluctance to eat in cold conditions, and a pale tongue with white moist coating and a wiry-slow pulse. Horses with constitutional spleen-stomach yang vacuity may show increased digestive sensitivity in cold weather as the external cold compounds the internal yang vacuity, making the middle jiao more vulnerable to cold obstruction and qi stagnation. An Zhong San's warming and regulating strategy addresses both the external cold trigger and the underlying constitutional yang insufficiency. Veterinary tongue and pulse confirmation of the spleen-stomach cold pattern is important before initiating treatment, as digestive discomfort in horses can have multiple causes, and the formula's warming nature warrants pattern confirmation to avoid use in horses with stomach heat or yin vacuity patterns.
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