King Cobra - Venom

Venom

The venom of the king cobra consists primarily of neurotoxins, but it also contains cardiotoxic and some other compounds. Similar to other venomous creatures, toxic constituents inside the venom are mainly proteins and polypeptides.

In common with those of other venomous snakes, LD₅₀ values of the king cobra venom vary with different injection methods and toxicological research, although 1.7 mg/kg of subcutaneous injection, 1.31 mg/kg of Intravenous injection and 1.644 mg/kg of Intraperitoneal injection are common data found in toxicological sources (Australian Venom and Toxin database and Dr. Bryan Grieg Fry's sources). Engelmann listed the Intravenous LD₅₀ at 0.9 mg/kg and the mean value of subcutaneous LD₅₀ of five wild-caught king cobras in Southeast Asia was determined as 1.93 mg/kg in another study. The book "Snake of medical importance" (1990) gives a datum of 0.34 mg/kg of intramuscular injection for the specimens found in China in a passing sentence. Besides, toxicity may vary among individuals coming from different geographical localities.

This species is capable of delivering a fatal bite and a large quantity of venom can be injected with a dose anywhere from 200–500 mg on average, and up to 7 ml. Engelmann and Obst (1981) list the average venom yield at 420 mg (dry weight). A large quantity of antivenom may be needed to reverse the progression of symptoms developed if bitten by a king cobra.

During a bite, venom is forced through the snake's 1.25 to 1.5 cm (0.49 to 0.59 in) fangs into the wound, and the toxins begin to attack the victim's central nervous system. Symptoms may include severe pain, blurred vision, vertigo, drowsiness, and paralysis. Envenomation progresses to cardiovascular collapse, and the victim falls into a coma. Death soon follows due to respiratory failure. Moreover, envenomation from king cobras is clinically known to cause renal failure as observed from some snakebite precedents of this species.

The mortality rate and death time resulting from a bite can vary sharply with many factors including the quantity of venom delivered, the site of bite and the health state of the victim. Data provided by different sources, which may come from different regions, could also have a significant difference: while a report mentions that many bites from king cobras involved non-fatal amounts of venom, another report of clinical statistics released by the South Indian Hospital reveals that actually two-thirds of the bitten patients received severe bites from this species. According to the University of Adelaide Department of Toxicology, an untreated bite has a mortality rate of 50-60%. Bites from a king cobra may result in a rapid fatality which can be as early as 30 minutes after envenomation, depending upon several factors including the nature and severity of the bites. A bite from a king cobra is said to be capable of bringing down an elephant.

There are two types of antivenom made specifically to treat king cobra envenomations. The Red Cross in Thailand manufactures one, and the Central Research Institute in India manufactures the other; however, both are made in small quantities and are not widely available. Ohanin, a protein component of the venom, causes hypolocomotion and hyperalgesia in mammals. Other components have cardiotoxic, cytotoxic and neurotoxic effects. In Thailand, a concoction of alcohol and the ground root of turmeric is ingested, which has been clinically shown to create a strong resilience against the venom of the king cobra, and other snakes with neurotoxic venom.

The haditoxin in the king cobra venom was discovered by Singaporean scientists to be structurally unique and can have unique pharmacological properties. Biochemical studies confirmed it existed as a noncovalent dimer species in solution. Its structural similarity to short-chain α-neurotoxins and κ-neurotoxins notwithstanding, haditoxin exhibited unique blockade of α7-nAChRs (IC50 180 nM), which is recognized by neither short-chain α-neurotoxins nor κ-neurotoxins.