Approving a Colleague's 小青龙汤 Prescription for a Dry Cough
A 62-year-old retired accountant has had a dry, tickling cough for five weeks following a viral illness. He coughs mostly at night and after speaking, with scanty sticky sputum that is hard to expectorate. He reports night sweats, a dry mouth and throat, a metallic taste, and constipation every second or third day. He has hypertension (158/94 mmHg on amlodipine 5 mg) and insomnia, and drinks three cups of coffee daily. The tongue is red with a peeled, mirror-like central coating and no moisture; the pulse is thin and rapid at 96 beats per minute. A colleague has already written a seven-day prescription of 小青龙汤 containing 麻黄 9 g, 桂枝 9 g, 干姜 9 g, 细辛 9 g, 五味子 6 g, 半夏 9 g, 白芍 9 g and 炙甘草 6 g, and the patient wants your approval before taking it.
1. Explain why 小青龙汤 does not fit this patient, using the specific signs and the formula's construction.
Read the worked answer
What the formula is for. 小青龙汤 treats wind-cold on the exterior with cold-fluid retention in the interior (外寒内饮): chills, absence of sweating, stuffy nose, cough with profuse thin white frothy sputum, a sense of fluid in the chest, pale tongue with white slippery coating, and a floating tight pulse. Its construction is warming and drying by design - 麻黄 and 桂枝 disperse cold, 干姜 and 细辛 warm and dry, 半夏 transforms thin fluid.
Why it does not fit
- Five weeks of dry cough with scanty sticky sputum is the opposite of profuse thin fluid.
- Night sweats, dry mouth and throat, metallic taste, constipation, a red tongue with a peeled mirror coating, and a thin rapid pulse indicate lung-stomach yin deficiency with dryness, possibly with residual heat.
- There is no exterior pattern: no chills, no fever, no floating pulse.
- Warming, drying, dispersing herbs would consume the remaining fluids. Expect worse night sweats, a drier throat, insomnia, constipation, and possibly blood-streaked sputum.
The principle. Treatment should nourish yin, moisten the lung, descend cough and clear residual heat. This is a case where the formula is internally coherent but aimed at a pattern the patient does not have. Approving it makes you the prescriber of record for a foreseeable deterioration.
2. Identify the dosing and safety problems in the colleague's prescription.
Read the worked answer
细辛 9 g is the most serious problem. The pharmacopoeial range is about 1–3 g ('细辛不过钱'). Above that there is risk of central nervous system and respiratory depression: numbness of tongue and lips, nausea, sweating, agitation, then drowsiness and arrhythmia. Asarum also carries trace aristolochic acid concerns, so species and quality matter. Nine grams would require explicit justification, extended decoction and close supervision - none of which exists in a routine outpatient setting.
麻黄 9 g with blood pressure 158/94, insomnia and three coffees daily is a poor combination. Ephedrine raises blood pressure and heart rate and worsens insomnia; it is contraindicated in uncontrolled hypertension.
干姜 9 g with 桂枝 9 g adds further drying heat to a tongue with no coating at all.
Process problems
- No documented tongue and pulse examination by the prescriber in the notes provided.
- No review date, no red-flag advice, no record of the patient's antihypertensive medication.
- 五味子 is astringent and may be appropriate later, but not while residual heat is uncleared.
Action. Do not approve. Explain the mismatch in plain language, notify the colleague, and record both conversations, including the patient's decision.
3. Propose a replacement strategy and a review plan.
Read the worked answer
Principle: nourish yin, moisten the lung, descend cough, clear any residual heat.
Base formula - 沙参麦冬汤 modified
- 北沙参 12 g, 麦冬 12 g, 玉竹 10 g - moisten lung and stomach.
- 桑叶 10 g, 天花粉 10 g - clear and generate fluids for the dry throat.
- 川贝母 3 g powdered and swallowed, or 枇杷叶 10 g - descend cough.
- 地骨皮 10 g if low-grade heat with night sweats persists.
- 五味子 3–6 g only if the cough is exhausting and no phlegm is retained.
Modifications for this patient
- Constipation: 火麻仁 10 g or 瓜蒌仁 10 g rather than a harsh purgative.
- Insomnia: 酸枣仁 15 g, and reduce coffee - this matters as much as the herbs.
- Hypertension: keep 麻黄 out entirely and avoid high-dose 甘草.
Review at 5–7 days, checking night cough frequency, sputum character, tongue moisture and coating, stool, sleep, and home blood pressure readings. If the coating has not begun to return or the cough is unchanged by two weeks, reassess for other causes - post-nasal drip, reflux, ACE-inhibitor cough, pertussis, tuberculosis - and refer for chest imaging. Give red-flag advice: haemoptysis, weight loss, fever or breathlessness require urgent assessment.