Tuesday, September 21, 2010

The Coral Snake Antivenom Shortage and the Economics of FAB and IgG Antivenoms

We are fast approaching October 31st, 2010.  Besides being Halloween, it is the day when the last batch of Coral Snake antivenom produced by Wyeth goes out of date. Wyeth is now owned by Pfizer. Coral Snake antivenom was first approved for sale in 1967. Wyeth maintained production of whole IgG coral snake antivenom for almost 40 years. However, Wyeth ceased production of antivenom (for both coral snakes and pit vipers) in 2003. Shutting down Wyeth’s antivenom production was highly questionable and surrounded by politics. Wyeth’s operation was not profitable, and the company worked with the FDA to produce a five year supply of antivenom. In 2008 the FDA extended the expiration date on the existing antivenom for a year, and extended it again for another year. Studies on other snake antivenoms have shown it remains effective well passed the expatriation date. Unfortunately, no other pharmaceutical company has come forward to produce the antivenom.

The Mexican drug manufacturer, the  Instituto Bioclon in Huehuetoca, Mexico, has a coral snake antivenom, believe by some to be more effective than Wyeth’s whole IgG antivenom.  Its brand name is  Coralmyn®, and is not currently licensed for sale by the FDA. The tests required for licensing are estimated to cost $3-5 million, and because coral snake envenomation is so rare it could be decades for Bioclon to recover its investment. Coralmyn® is an FAB antivenom, manufactured by taking the whole IgG molecule produced in a horse or sheep and digesting them with an enzyme (pepsin or papain), and then recovering the fragments that bind to the toxins in the snake venom. This type of antivenom is relatively new and is thought to reduce the probability of side effects (anaphylactoid reactions) seen with the whole IgG antivenom used for the past 110 years.

CroFab is the antivenom now used for North American pit viper bites and has been shown to be effective in serious envenomations. However, the economics of the FAB antivenoms versus the whole IgG antivenoms is highly questionable. A vial of FAB antivenom can cost US$1200, while a vial of whole IgG antivenom can be produced for as little as US$40. Whole IgG antivenoms are a century old technology that is highly effective and relatively inexpensive. There is not a lot of money to be made from the production of whole IgG antivenom in the USA because there are relatively few envenomations in any given year. However, if you are the unfortunate person to be bitten, it is your life that is at stake. This is an excellent example of the failure of the market to produce needed medicine, and why medicine for profit is a wrong-headed approach to healthcare. And, yes countries in South America, Africa, and Asia do produce whole IgG antivenoms for reasonable costs and control the side effects with epinephrine that costs about US$2.

Brown, N. and J. Landon, 2010. Antivenom: the most cost-effective treatment in the world? Toxicon 55(7):1405-1407.

Murphy, J. C. 2010. Secrets of the Snake Charmer. Bloomington, 400 pp. (Chapter 6)

Simpson, I. D. and R. L. Norris, 2009. The global snakebite crisis a public-health issue misunderstood, not neglected. Wilderness and Environmental Medicine 20:43-56.

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