• 
• 

Three Part Question

In [well adults who have been bitten by a venomous snake] do [prophylactic antibiotics] reduce [the incidence of infection]?

Clinical Scenario

A 26 year old man attends the emergency department having been bitten on his right hand 30 minutes previously by his pet a venomous snake. Examination reveals extensive swelling of his forearm with lymphangitis, hypotension and gingival bleeding. He has no relevant previous medical history and is fully anti – tetanus immunised. You know there is the potential for infection from the snakes fangs and oropharynx, as well as contamination from the victim's skin and clothing. You thoroughly clean the wound with local wound toilet, and are happy that there is no fang left in situ. You wonder if prophylactic antibiotics are indicated to reduce the risk of infection.

Search Strategy

Medline 1966–11/01 using the OVID interface.
(exp snake bites OR snake bite$.mp) AND (exp Antibiotics OR anti-biotics OR antibiotic$.mp) LIMIT to human AND English.

Search Outcome

60 papers of which 3 were relevant to the original question.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Clark RF et al, 1993, USA	54 patients who attended with crotalid (rattlesnake) envonamations observed for signs of infection Data available for 41	Prospective observational study	Presence of infection	3% pts without antibiotics developed an infection, compared with 22% (2/9) who were receiving antibiotics	Follow up involved telephone consultation as well as direct observation Very small numbers
Kerrigan KR et al, 1997, Ecuador	114 pts – 59 randomly assigned to receive antibiotics	PRCT	Presence of infection as shown by abscess formation	10.2% of treated patients developed abscesses compared with 5.5% of the untreated P = 0.558	No blinding Not controlled for other variables e.g. anti venin administration or surgical debridement Initiation of antibiotic treatment delayed
Blaylock RS, 1999, South Africa	363 patients presenting with snake bites – both venomous and non venomous (12%) (310 files available) requiring admission to hospital with swelling	Prospective trial	% receiving antiobiotics	84.8% of pts received no antibiotics	Not PRCT ?Comparable groups Extrapolation and interpretation of results is controversial Very little raw result data provided
			Compared the length of stay in the 2 groups, (antibiotics vs no antibiotics) further subdivided and analysed depending on main symptomatology – swelling, weakness	No difference in length of stay between the groups - this is interpreted as reflecting no difference in infection rate

Comment(s)

Most of the trials involved small numbers and were affected by the use of antivenin, which in itself has antibactericidal activity. There is concern that use of antibiotics prophylacticaly will have little impact on further infection but may give rise to side effects, is not cost effective and may select out more resistant organisms. These studies again confirm the low event rate for infection following snakebite from venomous snakes.

Clinical Bottom Line

Prophylactic antibiotics are not required in snake bites from venomous snakes.

References

1. Clark RF, Selden BS, Furbee B. The incidence of Wound Infection Following Crotalid Envenomation. J Emerg Med 1993;11(5):583–6.
2. Kerrigan KR, Mertz BL, Nelson SJ et al. Antibiotic Prophylaxis for Pit Viper Envenomation: Prospective, Controlled Trial. World J Surg 1997:21(4)369-73.
3. Blaylock RS. Antibiotic Use and Infection in Snakebite Victims. South African Med J 1999;89(8):874-6.