Xiao Qing Long Tang

Xiao Qing Long Tang (Minor Bluegreen Dragon Decoction), from the Shang Han Lun (Discussion of Cold-Induced Disorders) by Zhang Zhong-Jing.

Actions: Releases the exterior and dispels yin (invisible phlegm); Relieves wheezing and coughing.

Presentation: Wind-cold at the exterior with water accumulation in the interior: aversion to cold and fever, absence of perspiration, coughing and wheezing with profuse, clear, watery sputum, a stifling sensation in the chest, heaviness and pain of the body, edema of the face and limbs, a white, slippery tongue coating, and a superficial pulse.

Cautions:

• Not for prolonged use; stop once effective.
• Contraindicated in heat with sore throat or rapid pulse, wind-heat or early wen bing, yin deficiency with dry cough or thirst, phlegm-heat with thick yellow sputum, blood-streaked sputum, or cough with yellow sputum, thirst, red tongue, yellow coating and rapid pulse.
• Relatively strong: prescribe Xi Xin carefully (potentially toxic at high dose) and avoid large doses of Wu Wei Zi (may retain pathogens).
• Few side effects: dry mouth, sedation and drowsiness (attributed to H1 and muscarinic receptor blockade).
• Rare self-limiting gastrointestinal upset (nausea, vomiting, diarrhea) and skin itching, resolving on discontinuation.

Herb–drug interactions:

• Fluticasone: in 42 asthma patients, inhaled fluticasone plus oral Xiao Qing Long Tang gave better pulmonary function and serum IL-16 results than either alone
• Carbamazepine (rats): simultaneous dosing delayed absorption without changing peak, AUC or half-life; 1-week pretreatment increased Tmax and elimination rate constant; protein binding unaffected

Pharmacological effects reported:

• Antiasthmatic: beta2-adrenoceptor stimulation (bronchorelaxation) and inhibition of eosinophil infiltration into airways
• Antiallergic: inhibits histamine release, suppresses Th2 differentiation, inhibits mast cells and allergen-induced TNF-alpha synthesis
• Antiviral: prophylaxis and treatment of influenza in allergic pulmonary inflammation models by raising nasal/bronchoalveolar IgA and activating T cells; no direct antiviral action
• Immunomodulatory: reduced airway cell counts and eosinophil infiltration and down-regulated lymphocyte responses in allergen-sensitized mice
• Adrenal cortex: oral 0.05 g/kg raised plasma cortisol (36/30/25%) and ACTH (18/18/23%) at 30/60/120 min vs placebo
• Sympathomimetic: duodenal doses of 0.5-2 g/kg in dogs increased respiratory rate, heart rate and blood pressure and decreased blood flow

Source: Chen JK, Chen TT. Chinese Herbal Formulas and Applications: Pharmacological Effects & Clinical Research. Art of Medicine Press, 2009, p. 74.

Source text: cook Ma Huang in 10 cups [2,000 mL] water to 8 cups [1,600 mL], skim foam, add the rest and reduce to 3 cups [600 mL]; take 1 cup [200 mL] warm. Today use bracketed doses.