Chan su (sometimes transliterated "ch'an su" - "senso" in Japanese) is a traditional Chinese medicine derived from the venom of various toad species, especially Duttaphrynus melanostictus and Bufo gargarizans.1 The term "chan su" sometimes refers to the venom-infused skin of the toad, but more often refers to the venom itself, and is frequently translated as "toad venom". Chan su has been used by itself or combined with other ingredients such as in the traditional Japanese heart medicine kyushin.

Varying potencies are associated with different toad species. A recent analysis found the venom harvested from Bufo gargarizans in central China to be of the highest quality for traditional medicinal use.8

Chan su contains numerous bioactive chemicals including the psychoactive chemical bufotenin, various bufotoxins, bufotenidin, cinobufalin, and many others.2 Unlike the venom of Bufo alvarius, the venom of D. melanostrictus and B. gargarizans are not believed to contain 5-MeO-DMT. Traditional Chinese Medicine (TCM) references do not describe chan su as possessing psychoactive properties, probably because oral doses of chan su do not contain large enough quantities of bufotenin to be active. Ingestion of enough chan su to be psychoactive could be life-threatening due to other ingredients. It is unknown if chan su has ever been smoked. TCM textbooks are largely regulated by the Chinese government and might not describe psychoactivity even if a substance had been observed to be psychoactive.

Chan su is traditionally ingested orally or applied topically to "resolve toxicity", reduce swelling, and alleviate pain. It is said to "expel summerheat and dampness, open the orifices, and awaken the spirit [shen]". Chan su dosage in pills and powders is usually between .01 to .03 grams.1,2

Chan su acts as a CNS stimulant and exerts cardiopulmonary effects. Some of the toad-derived bufadienolides show structural similarities to digoxin/digitalis. Like digitalis, chan su can be cardiotoxic and has resulted in several known deaths. The LD50 (the dose at which 50% of experimental animals died) for chan su in mice is 41.0 mg/kg IV, 96.6 mg/kg SC, and 26.81 IP.2

Chan su has been sold in modern times as an aphrodisiac.3 The so-called "aphrodisiacal" qualities of chan su are associated with transdermal application to the penis, which may numb sensation and delay ejaculation.6 Four individuals died in the early 1990s in the United States after orally ingesting chan su that had been marketed as a topical aphrodisiac under the names "stone", "lovestone", and "rock hard".4,5 These subjects orally ingested the chan su, apparently under the mistaken belief that it would enhance the aphrodisiacal qualities, and were killed by the cardioactive effects.

One TCM textbook recommends treating chan su poisoning by "pressing the juice from 120g of fresh Phragmitis Rhizoma (xian lu gen) or an infusion of 15g of Rhei Radix et Rhizoma (da huang)."1 Another recommends (in addition to the above) that "Early stage overdose can be treated via emetic methods followed by ingestion of egg whites. Ingestion of a large amount of water or concentrated tea is also beneficial."2

Chan su has also received some clinical support for use in treating some cancers.9

Chan su is frequently described as having a long history of use. As early as 1929, Jensen and Chen described chan su in a scientific journal as "the dried venom of the Chinese toad".7 In this early article, the cardio-stimulatory effects of chan su are described. The authors attributed these affects to epinephrine, which they successfully isolated from the substance. Chan su is now known to contains several cardioactive steroids in addition to epinephrine some of which also function as local anesthetics.6

As of April 2007, Chan su is available for purchase online. One Internet vendor markets it as "Toad Capsule" (Hua chan su jiao nang) and describes it as "Dried toad's skin" for use in "Resolving toxin, dispersing swellings, stopping pains." They also state that "It can be used for medium and terminal stages of cancer. The product could be also used to treat chronic hepatitis B, etc."

Bufotenin, which may be found in chan su, is currently listed as a Schedule I controlled substance in the United States. Chan su could therefore be technically illegal to buy, sell, or possess in the U.S.

Update (Sep 2008): A man in Chesterfield County, Virginia was found to be in possession of a "thumb-sized black rock" of Love Stone when his car was searched during a traffic stop. This discovery led to the prosecution of the alleged Love Stone vendor, DBW, who sold it along with various other herbal remedies and magic implements at her store in Richmond, Virginia.10 DBW was prosecuted for sale of a Schedule I substance, but charges were later dropped.11