Pharmacology of snake venoms

Botanical treatments for snakebite in rural Ghana: A narrative review

ETHNOPHARMACOLOGICAL RELEVANCE

In the countryside, there are some limitations with the use of venom antisera to manage snake bites. Due to poor access to healthcare and as a result of the difficulty in receiving treatment for cases of snake bites, most rural people in Ghana, a West African country, rely on plant medicine as a first aid to manage cases of venomous snakebite. This calls for more research into the species of plants used to medically manage snakebite envenomation.

AIM OF THE STUDY

This review sought to present plants that are used in managing snakebite cases and also gather data supporting their use.

METHODOLOGY

This is a systematic search and review of information obtained from textbooks and databases such as PubMed and ScienceDirect between January 1975 and August 2020.

RESULTS

A search done identified 43 plant species and these were found to belong to 25 taxonomic families with the most frequent ones being, Fabaceae, Euphorbiaceae, Apocynaceae, and Solanaceae. Experimental data gathered indicate that among the many plants identified to be used to manage snakebites, only 5 were found with anti-venom in vitro and in vivo evidence-based data.

CONCLUSION

Data collated hint that a few plant species identified namely Anacardium occidentale, Euphorbia hirta, Mimosa pudica, Musa paradisiaca and Mangifera indica, work by targeting diverse physiopathological and biochemical processes involved in the clinical manifestations of snakebites. This review has also unearthed knowledge gaps that can form the basis for broad investigations and development of these and other medicinal plants into useful anti-venom medications.

Efeitos do soro antibotrópico nas alterações hemodinâmicas induzidas em cães pelo veneno de Bothrops moojeni

Para determinar o efeito do soro antibotrópico nas alterações hemodinâmicas utilizou-se 16 cães machos mestiços, sedados e mantidos intubados sob respiração espontânea. O soro antibotrópico foi eficaz para neutralizar a ação hipotensora, bem como evitou a queda do débito cardíaco e elevação da resistência vascular pulmonar, sem elevação da resistência vascular sistêmica, da frequência cardíaca e da pressão em capilar pulmonar nas condições experimentais acima assinaladas.

Crotalid snake envenomation

Over 5000 Americans suffer from snake bites annually, and of these, nearly one quarter are from poisonous species. Although these cases are undeniably reported, death appears to occur in only a few cases each year, and often reflects delay in obtaining medical care. Two families of venomous snake indigenous to the United States account for most envenomations: Crotalidae (pit vipers or new world vipers) and Elapidae. This article focuses on the snakes of the Crotalidae family.

Venomous snake bite: current concepts of treatment

The optimal treatment of venomous snake-bites remains controversial. Because of the variables involved in treatment, an ideal, prospective clinical trial likely will never be done. The purpose of this article is to review the available treatment methods and outline the treatment methods preferred in our institution for crotalidae envenomation.

Mojave rattlesnake envenomation: prolonged neurotoxicity and rhabdomyolysis

An 11-year-old girl presented to the emergency department with hypoventilation and shock after being bitten by a Mojave rattlesnake. Intubation was required, and she improved rapidly after fluid resuscitation and antivenom administration. She was extubated four hours after envenomation and did well. The patient subsequently developed increased weakness and cranial nerve paresis and required reintubation for respiratory failure at 30 hours after envenomation despite administration of 30 vials of antivenom. She improved after administration of additional antivenom and was extubated ten hours later. Twenty-four hours after envenomation, signs of rhabdomyolysis were noted with myoglobinuria and a creatine phosphokinase level of 96,400 units/L. Myoglobinuric renal failure was treated with mannitol, hydration, and alkalinization of the urine. The patient's renal and neurological functions improved steadily during the following three to four days. Neurotoxic and myotoxic effects of Mojave venom are known to occur but are not well documented in human beings. Recognition of potential complications from envenomation such as respiratory paralysis and rhabdomyolysis with myoglobinuric renal failure is critical.

Acro-osteolysis following snake and scorpion envenomation

Three cases of acro-osteolysis are described following snake bite and three after scorpion stings. This effect is consistent with tissue necrosis secondary to the enzymatic actions of the venom.

Mechanism of defibrination in humans after envenomation by the Eastern diamondback rattlesnake

We prospectively studied the hemostatic system of ten persons bitten by the Eastern diamondback rattlesnake (Crotalus adamanteus) during 1978-1980. Blood was drawn when the patients arrived in the emergency room and every 6 hr thereafter. All envenomated victims developed incoagulable blood (defined by a thrombin time greater than or equal to 120 sec, normal less than 20 sec). Platelet counts and plasma levels of antithrombin III and factors II and VIII were not drastically altered, which distinguished this disorder from classic disseminated intravascular coagulation. Fibrinogen levels were markedly decreased (mean coagulable level of 0 mg/dl and antigenic levels of 99 mg/dl). Plasminogen levels were 20% of normal, alpha-2-plasminogen inhibitor was 17% of normal, and plasminogen activator was 20 times normal. Levels of fibrin degradation products peaked at a mean of 7,680 micrograms/ml. The magnitude and duration of the coagulopathy were proportional to the clinical severity of envenomation. Treatment with antivenin blunted the coagulopathy. Because venom from the Eastern diamondback rattlesnake does not directly activate plasminogen, we conclude that coagulopathy following envenomation by that reptile appears to be due to partial proteolysis of fibrinogen with secondary activation of plasminogen by released plasminogen activator, probably of endothelial origin.

Envenomation by the Mojave rattlesnake (Crotalus scutulatus scutulatus) in southern Arizona, U.S.A

Fifteen cases of envenomation by the Mojave rattlesnake (Crotalus scutulatus scutulatus) are reviewed. Systemic effects were observed in eight patients, consisting of early hypotension (3), decreased plasma fibrinogen (3) and platelets (2), elevated fibrinolytic split products (3) and eyelid ptosis (1). Local venom effects were most common and included swelling (15), ecchymosis (10), bleb formation (6) and necrosis (3). Effects upon neuromuscular transmission were neither common nor a clinical problem. Treatment consisted of i.v. crystalloid solution (15) and antivenin (12).

Geographical variation in Crotalus scutulatus scutulatus (Mojave rattlesnake) venom properties

Individual venom samples were analyzed from 12 specimens of Crotalus scutulatus scutulatus, from north of Tucson to the extreme southeastern region of Arizona. Six of the specimens, from north of Tucson, produced venom lethal toxicity (i.p. LD50) values in mice of 2.0-6.0 mg/kg. These coincided with the values previously reported for C. s. scutulatus in the Phoenix, Arizona, region and designated as type B venom (Glenn and Straight, 1978). In contrast, the venom LD50 of six individuals from extreme southeastern Arizona, including one individual near Tucson, ranged from 0.22-0.46 mg/kg. This corresponds to the values for C. s. scutulatus venom previously reported and designated as type A venom (Glenn and Straight, 1978). Specimens with type A venom have been collected in California, Nevada, Utah and regions of Arizona. In addition to differences in lethal toxicity, the type B venom consistently exhibits a different protein profile, greater proteolytic activity, greater hemorrhagic activity and contains little or none of the major lethal toxin, Mojave toxin, compared to the type A venom. No external morphological characteristic could be found differentiating the type A venom specimens from the type B venom specimens. These findings further confirm the geographical variation of C. s. scutulatus venom in Arizona.

Snake venom action: are enzymes involved in it?

Enzymes were the first clearly recognized components of snake venoms. When several more were discovered, attempts were made to correlate venom action with enzymic functions. The last few years have seen most successful efforts in the identification, isolation and structrual elucidation of highly toxic polypeptides present in snake venoms, in particular of 'neurotoxins' and membrane-active toxins. Following this development the polypeptides were called the true toxic components and the enzymes lost their previous central position in venom pharmacology. The time, therefore, has come re-evaluate the role of enzymes in the complex interaction between snake and prey. While highly active polypeptides indeed dominate the actionof hydrophiid venoms, they appear to play a lesser role in crotalid venom action as compared with enzyme components. Enzymes are involved in many levels of venom action, e.g. by serving as spreading factors, of by producing very active agents, such as bradykinin and lysolecithins in tissues of preys or predators. Some toxins, e.g. the membrane-active polypeptides appear to participate in the interaction between membrane phospholipids and venom phospholipases. The classical neurotoxin, beta-bungarotoxin, has been recognized as a powerful phospholipase. Several instances are known which indicate that some enzymes potentiate the toxic action of others; the analysis of a single enzyme may, therefore, not fully reveal its biofunction. For 3 enzymes,ophidian L-amino acid oxicase, ATPpyrophosphatase, and acetylcholinesterase, some of the problems pertaining to venom toxicity are discussed.