Mian Hua Gen

Gossypol inhibits corticosteroid 11-beta-hydroxysteroid dehydrogenase, demonstrated in guinea pig kidney, producing a state resembling apparent mineralocorticoid excess in which cortisol is not inactivated at the mineralocorticoid receptor and renal potassium wasting follows. The Chinese randomised controlled male contraceptive trial specifically tested whether this could be blocked: neither potassium salt supplementation nor the potassium-sparing diuretic triamterene reversed or prevented the gossypol-related fall in serum potassium. The efficacy arm of the same trial found a statistically significant downward trend in serum potassium through twelve months of maintenance dosing. Clinical series from the Chinese programme documented hypokalaemic paralysis, and reported incidences of periodic paralysis of the order of 1 percent. This is not folklore and it is not a theoretical concern.

Hypokalaemia increases myocardial sensitivity to cardiac glycosides by reducing competition for the sodium-potassium ATPase, and is one of the classical precipitants of digoxin toxicity at an unchanged digoxin dose. Since gossypol causes potassium wasting through 11-beta-hydroxysteroid dehydrogenase inhibition, and since that hypokalaemia was not correctable by potassium salts or triamterene in trial conditions, the mechanistic chain from Mian Hua Gen to glycoside toxicity is direct even though no case series pairs the two explicitly.

Gossypol was tested as an oral male contraceptive in very large numbers of Chinese men with antifertility efficacy exceeding 99 percent. The reason it was abandoned rather than licensed was irreversibility: in the multicentre international dose-finding study, 8 of 43 men remained azoospermic one year after stopping the drug, only 12 of 19 at 7.5 mg per day and 10 of 24 at 10 mg per day recovered counts above 20 million per millilitre within twelve months, and every man with a varicocele failed to recover. Reported rates of permanent sterility across the wider literature run considerably higher. The World Health Organization's research programme concluded gossypol would not be acceptable as an antifertility drug. The crude root bark is not dose-controlled for gossypol, so this risk cannot be titrated.

Cotton root bark, specifically the part named in this record, has a long documented use as an abortifacient and emmenagogue, and the activity is attributed to its high gossypol content. In animals gossypol interrupts early pregnancy and early embryonic development, disturbs the oestrous cycle and impairs granulosa cell steroidogenesis. Superimposing it on a uterotonic drug is compounding two abortifacient effects, and using it in an undisclosed pregnancy is the more common real-world hazard.

Three distinct drugs sit close together in the pinyin. Mian Hua Gen is the cotton root (Radix Gossypii), the drug in this record. Mian Hua Zi is cottonseed, the commodity from which the gossypol used in the Chinese contraceptive programme was purified and the material behind gossypol poisoning of livestock fed cottonseed cake; it is the higher-risk part for reproductive toxicity in practice. Mu Mian refers to Bombax ceiba, a wholly unrelated Malvaceae tree whose flower and bark are used quite differently and which contains no gossypol. There is a further identity problem specific to the binomial: Gossypium hirsutum is a New World species, introduced repeatedly into China only between the 1860s and 1950 and not completely displacing the long-cultivated Asian diploid Gossypium arboreum until the 1950s. Any pre-modern Chinese record of cotton therefore describes Gossypium arboreum, not the species named here, and gossypol content differs between Gossypium species and cultivars.