Mohave Rattle Snake Envenomation Medication

Be prepared to support the patient's cardiovascular and respiratory systems after a Mohave rattlesnake or similar envenomation.

Class Summary

This agent neutralizes toxins from snakebites. Two antivenoms are available: Crotaline Fab antivenom (CroFab) and Antivenin Crotalidae Polyvalent. CroFab has been available since December 2000. CroFab is manufactured by Protherics, Inc, Nashville, Tenn, and distributed by Fougera, Melville, NY (800-231-0206). Antivenin Crotalidae Polyvalent, manufactured by Wyeth-Ayerst, is still available on the shelves of many hospital pharmacies but is no longer being produced. Whether production of Antivenin will resume is unknown. Meanwhile, another antivenom (Antivipmyn, manufactured by Instituto Bioclon S.A. de C.V.) has been FDA approved for experimental use and is currently undergoing phase III clinical trials.^[16]

CroFab (Crotalidae Polyvalent Immune Fab Ovine)

Appears to be more specific against rattlesnake venom and less allergenic than Antivenin (Crotalidae) Polyvalent. Remarkably effective for treatment of Venom A Mohave rattlesnake envenomation, probably because it is made using venom from Venom A Mohave rattlesnakes. Usual starting dose is 4-6 vials. Reconstitute each vial with 10 mL of sterile water for USP injection and mix by continuous swirling. Once CroFab goes into solution, the vials should be further diluted into a total volume of 250 mL of NS.

The infusion should be started slowly at a rate of 50 mL/h for the first 10 min. During initial infusion, observe patient for allergic reaction. If no reaction occurs, infusion rate may be increased up to 250 mL/h until completion. Observe the patient for up to 1 h after completion to determine if initial control of envenomation has been achieved, as defined by the arrest of progression of any and all components of the envenomation syndrome (ie, no further advancement of swelling, improvement of systemic effects, and improving coagulopathy).

Crotalidae polyvalent antivenom (equine)

Manufactured by Wyeth-Ayerst.

To mix antivenom, dissolve in 10 mL of warm saline by using gentle agitation. May take at least 20-90 min to dissolve. Further dilute it 1:2-4 (eg, mix 10 dissolved vials into a total dilution of 200 mL). Start the infusion at 1 mL/min for 10 min, closely monitoring for signs of allergic reaction. If no allergic reaction occurs, increase the rate to complete the infusion over 1 h. In children, run the infusion at 10 mL/kg/h. Diluting this antivenom in a greater volume of fluid and infusing it slowly may reduce the occurrence acute adverse reactions.

Routine premedication with antihistamines (H1 and H2 blockers) is recommended. Pretreatment with epinephrine (1:1000) 0.25 mL SC was shown to reduce acute adverse reactions to antivenom in one series, although the risks of epinephrine should be considered. Pretreatment with steroids is unlikely to prevent immediate reactions but may be helpful later if continued antivenom is indicated despite allergic reaction.

Class Summary

Patients should be immunized against tetanus.

Diphtheria-tetanus toxoid (dT)

Used to induce active immunity against tetanus in selected patients. The immunizing agent of choice for most adults and children >7 y are tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life.

Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen–containing product. In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is the mid thigh laterally.

Class Summary

Prophylactic antibiotics are probably not indicated routinely, although they are widely prescribed. Common etiologic bacteria suspected in snakebite wound infections include Pseudomonas aeruginosa species, Enterobacteriaceae species, Clostridium species, and Staphylococcus epidermidis. For infected wounds, empiric therapy may include ciprofloxacin (contraindicated in pediatric patients and pregnant women) as a single agent or a combination of ceftriaxone plus amoxicillin-clavulanate, pending wound culture and sensitivity results. Retained foreign bodies (eg, fang, other tooth) are a common cause of wound infection.

Ceftriaxone (Rocephin)

Third-generation cephalosporin with broad-spectrum gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding proteins.

Class Summary

Pain control is essential to quality patient care. It ensures patient comfort and promotes pulmonary toilet. Most analgesics have sedating properties, which are beneficial for patients with painful skin lesions. Use opiates with caution in unintubated patients because Mohave rattlesnake envenomation may cause respiratory difficulties.

Morphine (Astramorph, Duramorph, MS Contin)

DOC for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone.

Morphine sulfate administered IV may be dosed in a number of ways and is commonly titrated until the desired effect is obtained

Class Summary

These agents are used to treat minor allergic reactions and anaphylaxis to antivenom or venom. Diphenhydramine may be used to pretreat patients with prior documentation of minor allergic reactions. Antihistamines are used for premedication to antivenom administration to reduce acute adverse reactions (not for direct treatment of snakebite).

Diphenhydramine (Benadryl)

Used for symptomatic relief of allergic symptoms caused by histamine released in response to allergens.