The first and perhaps the most obvious use of snake venom is the production of anti-venom, the main technique used to produce anti-venom is known as the 'horse serum' method. Here the snake is milked of its venom as illustrated by the image, then a small non-lethal dose of the venom is injected into a horse. The horse is then given time to produce antibodies to the venom, a sample of blood is removed from the horse and the antibodies are extracted. This anti-venom can now be used to treat patients, although unfortunately a third of patients are allergic to this serum.

The protein contortrostatin which was extracted from the venom of the Southern Copperhead Viper Agkistrodon contortrix , has been shown to slow the growth of breast cancer cells (implanted into mice) by up to 70%². The protein is cytostatic (it prevents/slow tumour growth) rather than cytotoxic (kills tumour cells). The protein inhibits blood vessel development, the quick formation of which is essential to the rapid growth of tumour cells, this in turn prevents the growth of the tumour. 

Treatment of Blood Clots

       
 Taken from
http://animaldiversity.ummz.umich.edu/site/resources/ummz_herpetology/17.herp.jpg/view.html

Ancrod is a substance formulated from the venom of the Malayan pit viper Calloselasma rhodostoma, it inhibits fibrinogen which is involved in the production of fibrin (which forms blood clots). This enzyme is used by the snake to prevent blood clots forming in its prey whilst it is digesting them. This enzyme has played a major role in the development of ACE inhibitors (angiotensin converting enzyme inhibitors) which play a vital role in modern treatment of diseases such as strokes and heart attacks. In recent studies it was shown to improve recovery rates from strokes, 30% of patients given a placebo regained their mental faculties whilst using ancrod 40% did.

Other Areas of Interest

There are many other potential areas of research as to the use of snake venom in medicine    

for example there has been interest in the use of snake venom to treat Alzheimer's disease due to its ability to destroy nerves, and the potential use to destroy affected brain cells. Other areas of interest include the treatment of viruses as snake venom contain phospholipidases, which break down cell membranes, this could obviously be very useful in destroying viruses but it is very difficult to make this specific to viruses.