MLT has a long history but it is only recently that its effect mechanisms have started to be clarified. When a leech bites, hyaluronidase and collagenase allow access to the tissues and blood vessels; vasodilatation occurs by the action of histamine-like molecules; platelet functions, kinin activity, and the coagulation cascade are inhibited; and inflammatory reactions are suppressed. In addition, analgesic and antimicrobial effects are observed. Experiments on mice have shown a positive effect on wound/tissue repair.6, 9, 10, 11, 12, 13, 14
There is no consensus on the duration of application and number of simultaneously applied leeches. Medical professionals usually suggest a maximum of four or five leeches at the same time and a maximum duration of 6–8 hours, but these may vary due to physician’s clinical evaluation. The total duration of MLT is another unclarified issue. Physicians should consider the bleeding period after application, which may cause excess blood loss. Clinical monitoring and laboratory tests (blood count) are strongly recommended.7 The necessity for blood transfusion is related to the number of leeches applied, the duration of their application, patient conditions, and comorbidity.7, 53
Joint diseases such as osteoarthritis and epicondylitis, extremity vein diseases, and flap surgery (skin grafting) are major indications for MLT. MLT is also useful for soft-tissue and periorbital hematoma, purpura fulminans, macroglossia, penile replantation, postphlebitic syndrome, and ecchymosis. In addition, anticoagulants obtained from leeches are used for peripheral arterial occlusion and infectious myocarditis.9, 10, 11, 12, 13, 54, 55 Their use in dentistry has also been tested.56 MLT is not recommended when there is hemorrhagic diathesis, anticoagulant therapy, leukemia, bone narrow suppression, dialysis, cirrhosis, chemotherapy, radiotherapy, and cachexis.7
There are some potential complications with MLT. Allergies to leeches and their secretions should be considered.57 Infection is a serious condition that shows wide variability from local infections to bacteremia. Antibiotic prophylaxis significantly reduces the risk of leech-borne infections. Infectious agents vary depending on etiology, leech species, application area, and patient condition, but by far, Aeromonas spp. is the most common.7, 53, 58, 59, 60, 61, 62, 63 Furthermore, leeches can be vectors for some viruses, fungi and parasites in animals,64, 65, 66, 67 but it seems that application of leeches to humans also has infection potential.68, 69 However, these complications are rare and the most common adverse effects are itching and bleeding on the application area. These adverse effects can be eliminated by small interventions. Orthostatic hypotension and vasovagal symptoms may occur especially in elderly patients. Regional lymphadenopathy has also been reported. MLT usually leaves a scar, therefore, patients should be informed about this, especially before application to particular body parts.6, 7, 54, 70 Since this therapy has a potential risk of blood-transmitted diseases, reuse of leeches is strictly forbidden.71
In conclusion, MLT is a valuable traditional technique with strong biochemical actions. Although modes of action and bioactive substances still await further exploration, their utility in certain medical conditions is obvious. Indications and potential complications should be evaluated, including antibiotic prophylaxis and application frequency, and dosage and delivery timing depend on the patient and physician’s opinion. It must be noted that MLT is not a treatment method by itself, but it can be an important part of a multidisciplinary approach.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741396/
