Pao Fu Pian (炮附片; Páo Fù Piàn; Latin: Aconiti Lateralis Radix Praeparata; English: processed aconite daughter-root slices) is the processed piece of the daughter root of the aconite plant, a toxic medicinal material that is dried, then processed with salt and heat until its toxicity is markedly lowered — the dark, firm, slightly translucent slices that practitioners add to formulas when yang is collapsing and the limbs run cold. It is greatly hot, acrid with a sweet note, enters the Heart, Kidney, and Spleen channels, and its core actions are to warm and assist the yang, and to scatter cold and ease pain. The usual amount is 3–10 g in a decoction, and it is boiled first for about 30 minutes before the other herbs go in — a rule that is never skipped. It is a strongly active medicinal piece; the raw aconite side root is markedly toxic and is never used at home.

It is not Rou Gui. Cinnamon bark is also greatly hot, acrid, and sweet — it warms the yang, but it leans to warming the channels and guiding the fire home, better for warming the surface and unblocking the channels; this processed aconite slice reaches deep into the interior, warming and assisting the kidney yang and scattering deep cold. It is not a general warming herb; it acts within clear patterns. In yin-deficiency with internal heat — hot palms, night sweats, a red tongue — or in "upper heat lower cold" states, using it on your own is a poor match. Collapse with cold limbs, or a markedly unwell child, needs a clinic first. Do not take it yourself for a long time.

It is used most often for three patterns:

• Yang deficiency with cold — cold limbs, a cold body, pale urine, loose stools, fatigue and wanting to sleep, a pale tongue
• Cold pain in the kidney and belly — deep cold pain, worse with cold and better with warmth
• Yin-deficiency with internal heat, pregnancy, nursing, or children — seek care / skip it

Greatly hot, acrid, and strongly warming, it is not a daily "yang-warming tonic" to keep increasing. Warming when there is no yang deficiency, or in a yin-deficient body, burns the fluids instead of helping.

When yang is insufficient and cold gathers inside — the limbs run cold, the spirit is low, the pulse is deep and weak, or a deep cold pain sits in the belly — the body needs a warm-and-assist rather than a surface warming. Pao Fu Pian is greatly hot, acrid, and sweet. It warms the kidney yang, assists the heart yang, and scatters the deep cold, which is why it appears in Si Ni Tang (Four Reversal Decoction)–type formulas. It goes in deep and fast. In yin-deficiency with internal heat, or without yang deficiency, more makes it worse.

Pao Fu Pian is not a catch-all warming or pain herb. In yin-deficiency with internal heat, in pregnancy, or without yang deficiency, using it alone is a poor match. Whether it belongs in a formula, and at what dose, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.

1. Records in Classic Materia Medica

• Shen Nong Ben Cao Jing: lists Fu Zi in the lower class — "for wind-cold cough and rebellious qi, cold-damp convulsions and pains, and hardness and fullness; and for the broken and collapsed."
• Ming Yi Bie Lu: adds — "for lower-abdomen cold pain, cold hernia, kidney qi decline, and lassitude."
• Zhang Zhong Jing (Shang Han Lun): builds the yang-warming formulas — Si Ni Tang and others — with raw Fu Zi first-boiled.
• Ben Cao Gang Mu: stresses that Fu Zi must be processed before use and paired with Gan Jiang and Gan Cao.
• Zhong Hua Ben Cao: consolidates the records — Pao Fu Pian is the processed piece, warming and assisting the yang and scattering cold.

2. How Views of Its Nature Changed

Han-dynasty doctors like Zhang Zhong Jing used raw Fu Zi first-boiled for yang collapse; later generations kept stressing the toxicity — the processing became a fixed rule, with salt-and-heat processing lowering the toxicity while keeping the warming; by the Ming-Qing period doctors emphasized the yin-deficiency warning — greatly hot herbs should not be used in yin-deficient bodies. The range keeps its scope clear and its warning strong.

1. Main Chemical Constituents

Detected in the aconite root are aconite alkaloids (the main toxic group), polysaccharides, and some lipids. The alkaloids are both the active and the toxic group — in animal hearts the alkaloids affect the rhythm, which is why the dose and the first-boiling rule are decisive; after processing, the toxic alkaloids are partly hydrolyzed and lowered. No sufficient human clinical study yet defines the mechanism and dose relationship.

2. Current Research Directions

Current work centers on two directions: the cardiac and warming mechanism — the alkaloids affect the heart rhythm and the blood flow; and the toxicity change after processing — heat hydrolysis lowers the toxic alkaloids. Most of this is at the component-analysis and animal stage and still needs human verification; the clinical practice still relies on the first-boiling rule and careful dose.

3. Limitations of Current Research

• Lab results are not clinical efficacy — the human environment differs greatly from animals and cell cultures.
• Extracts are not decoction pieces — dose, form, and absorption differ clearly from the clinical piece.
• Doses and preparations vary between studies — results differ and cannot be unified.
• One component does not define the whole herb — the piece acts as a team of constituents, including the toxic group.