Medicinal leeches, also known as Hirudo Medicinalis or Shui Zhi in Pinyin, can be used as a Chinese herb after they are dried and processed. That’s to say, clinically this aquatic animal is commonly used for treating stroke, hypertension, blood stasis, amenorrhea, bruises and other ailments. Medical leech contains hirudin, which can delay and impede blood clotting, namely anti-clotting effect. In recent years, its preparations have been discovered with special effect on prevention and treatment of cardiovascular disease and cancer. In the past most of medicinal leeches used to be fished in the wild but now it is mainly grown in farm with the decreasing natural resources due to pollution of the environment. This small animal is quite annoying since it can stick on you and suck your blood. However, its medical uses are enormous. So, do you know what are leeches used for in medicine? How are leeches used in medicine?
What are medicinal leeches?
From the perspective of traditional Chinese medicine, medicinal leeches mainly refer to the dried body of a few medicinal leech species, including Whitmania pigra whitman, Hirudo nipponica Whitman, and Whitmania acranulata Whitman. It is produced in most parts of China. Most of them are wild and captured in summer and autumn. After capturing, it still needs to be washed, scalded to death with boiling water, cut, and dried at a low heat or in the sun. Medicinally Hirudo seu Whitmaniae is used raw or scalded with talcum powder.
Dried whitmania pigra whitman is in the shape of a flattened spindle, 4 to 10cm long, 0.5 to 2cm wide, and with many segments. Back is in the color of dark brown or dark brown and slightly elevated. After soaking the water, it shows visible black spots arranged in five vertical stripes. Venter is flat and brownish-yellow. Both sides are brownish yellow. Front end is slightly pointed and the rear end is blunt. Both ends have a sucker respectively. The former sucker is not obvious while the back sucker is bigger. Its dried body is brittle, slightly fishy, easily broken, and with gelatinous section. Main habitats include paddy fields, rivers, and lakes.
Dried Hirudo nipponica Whitman is prolate, cylindrical, mostly curved and twisting, 2 to 5cm long, and 0.2 to 0.3cm wide. Main habitats are paddy fields and swamps.
Dried Whitmania acranulata Whitman is narrow, flat, 5 to 12cm long, and 0.1 to 0.5cm wide.
Hirudo nipponica (Whitman) and Whitmania pigra (Whitman) contain 17 amino acids, of which 7 kinds are essential amino acids and account for more than 39% of total amino acid content. Main amino acids are glutamic acid, aspartic acid, leucine, lysine, and valine. The total amino acid content is about 49% of dry weight. It mainly contains protein, heparin, antithrombin, and an anticoagulant substance called hirudin found in fresh leech saliva. In addition, it also contains higher content of essential elements (sodium, potassium, calcium, and magnesium) and other 28 kinds of trace elements (iron, manganese, zinc, silicon, aluminum, and others).
Medicinal leech benefits
1,500 years ago, the Egyptians pioneered the practice of bloodletting with medicinal leeches. In the beginning of the last century, the Europeans were more superstitious and believed that medicinal leech could suck the sick blood from the body so that they turned to medicinal leech therapy no matter what diseases they suffered from. Later this superstitious belief was gradually abandoned with the development of modern medicine.
In recent years the new use of leeches in medicine is getting more and more attention since its salivary glands have been found with anticoagulant hirudin and histamine-like substance that can dilate the blood vessels. As a result, plastic surgeons use medical grade leeches to eliminate blood stasis in vascular occlusion zone after the surgery. By doing so, it can reduce necrosis and thereby improve the success rate of breast tissue transplantation and breast augmentation. What’s more, leeches in modern medicine can greatly improve the success rate of replanting or transplanting fingers, toes, ears, nose, etc. by sucking blood to smooth the vein.
To better know about the leeches used in medicine, first off you’d better figure out what hirudin is. Hirudin is a low molecular weight (7000) polypeptide that consists of 65 amino acids. Hirudin is the most effective natural anticoagulant that is ever known so far. Its anticoagulant, thrombolytic effect, which is also known as activating blood and removing blood-stasis action in TCM, is better than that of heparin. Hence, it shows superior health benefits and promising prospect on dealing with a variety of diseases that lack antithrombin, such as septic shock, atherosclerosis, cerebral infarction, cardiovascular disease, hypertension, ophthalmic diseases, and so on.
Modern pharmacology of medical leeches decoction
1) It has strong anti-clotting effect on the blood, which can significantly prolong fibrin’s coagulation time;
2) Its extract and hirudin can significantly inhibit platelet aggregation, inhibit thrombosis in rats’ body, and have a good therapeutic effect to disseminated intravascular coagulation;
3) It can improve blood rheology, lower blood pressure, reverse or slow atherosclerotic plaque progression, increase myocardial nutritional blood flow, resist pituitrin-induced abnormal heart rate or significant ST-T wave changes;
4) It can promote the absorption of brain hematoma, reduce inflammation and edema of the surrounding brain tissue, relieve intracranial pressure, improve local blood circulation, and protect the brain from damage;
5) It can obviously inhibit subcutaneous hematoma and terminate pregnancy;
6) Hirudin has inhibitory effect on tumor cells;
7) It has protective effect on renal ischemia, reduce levels of serum urea nitrogen and creatinine, and greatly lower the elevated serum tumor necrosis factor.
Medicinal leech therapy on herbal remedies
The Chinese Materia Medica says that medicinal leeches are salty and bitter in flavor and neutral and toxic in nature. It covers liver meridian. Essential functions are breaking-blood to expel stasis and stimulating the menstrual flow to eliminate abdominal mass. Main medicinal leeches uses and indications include amenorrhea due to blood stasis, gynecological mass in abdomen, and bruises.
1) Di Dang Tang from Jin Gui Yao Lue (Essential Prescriptions of the Golden Coffer). It is formulated with Meng Chong (Gadfly), Tao Ren (Peach Seed), and Da Huang (rhubarb) to treat light menstrual blood flow in women or full bladder due to blood stasis.
2) Tao Ren Wan from Tai Ping Sheng Hui Fang (Taiping Holy Prescriptions for Universal Relief). It is combined with Peach Seed, Gadfly, and rhubarb to cure stasis-induced short or scanty periods and fullness in heart and abdomen.
3) Di Huang Tong Jing Wan from Fu Ren Liang Fang (Fine Formulas for Women). It is matched with Shu Di Huang (Rehmannia Root), Gadfly, and Peach Seed to heal delayed menstruation, an excessive flow of lochia after delivery, and pain in navel or abdomen.
4) Duo Ming San from Ji Sheng Fang (Life-saving prescriptions). It is coupled with rhubarb and Qian Niu Zi (Black Morning Glory Flower Seeds) to treat metal-inflicted wound, traumatic injury, or blood stasis, abdominal pain, and retention of urine and stool due to internal injury.
Research on medicinal use of leeches
Today, leeches for medicinal purposes are also used in the treatment of coronary heart disease, angina, hyperlipidemia, cerebral infarction, hemiplegia, pulmonary heart disease, asthma, liver cirrhosis, kidney disease, polycythemia vera, and some men’s common diseases.
a) 100 cases of coronary heart disease and angina have been treated with medicinal leeches tablets, 0.75g crude drug each, 2 to 4 tablets each time, and 3 times a day. The result showed that 34 cases were markedly improved, 56 cases were improved, 9 cases were ineffective, and 1 case became worse. And the ECG showed that 15 cases returned to normal, 44 cases were improved, and 37 cases were ineffective;
b) 150 cases of hyperlipidemia have been treated with raw medicinal leech powder capsules, 0.25g crude drug each, 4 pieces each time, 3 times a day, taken after meals, and 4 weeks as a course of treatment. The result showed that serum cholesterol dropped from averaged 5.398±1.084mmol/L to 4.953±0.923mmol/L (p<0.01) and serum triglycerides decreased from averaged 2.214±0.902mmol/L to 1.612±0.601mm0l/L; C) 50 cases of cerebral infarction have ever been treated with medicinal leeches oral solution, 3g crude drug each 10ml. And the result showed that 10 cases were cured, 28 cases were markedly effective, and 11 cases were effective. The total effective rate was 98%.
Medicinal leeches side effects and contraindications
0.5, 1.0g/kg medicinal leeches decoction was fed daily to mice that have been pregnant for 7 to 11 days. Weight loss occurred in all the fetal. And it also showed that this drug had an obvious teratogenic effect and increased the proportion of stillbirths and fetal resorption. That’s to say, it has an obvious effect of abortion in mice. TCM wise, it shouldn’t be taken during women’s menstrual period and by pregnant women and people with weak physique and bleeding tendency.
a) Tian Jin Yi Yao Za Zhi (Tianjin medical magazine), 1980;(4):238;
b) Bei Jing Zhong Yi Za Zhi (Beijing Journal of Chinese Medicine), 1989;(1):21;
c) Jiang Su Zhong Yi Za Zhi (Jiangsu Journal of Chinese Medicine), 1987;8(4):11.