Category Archives: spider

Brown Recluse Bites

Last October, a report of death by loxoscelism was reported in Annals.  It’s a sad story about a previously healthy 3 year old girl who was bitten by a witnessed brown recluse in Tennessee.  She went to a rural ED, was evaluated and discharged.  Only physical finding at that time was small red patch on the right breast.  Later that evening she developed signs of systemic loxoscelism, then the following morning evidence of myoglobinuria.  Went to Vanderbilt ED, where her initial labs of WBC 20.7, Hgb 9.5, 2+ spherocytes, and platelets of 54 were concerning.  INR was 1.8.  CMP was hemolyzed of course. They started transfusing, but sadly, she became apneic and pulseless shortly after, and was unable to be resuscitated.  Autopsy was consistent with systemic loxoscelism.

Emergency Department Death from Systemic Loxoscelism

Thankfully, loxoscelism deaths are rare (or rarely diagnosed!) in the US.  Current recommendations for treatment of systemic loxoscelism are aggressive supportive care, with blood products as needed.  No antivenom available in the US, but may help those in South America.

What about treating the more common incidences of cutanous loxoscelism? Sadly, the literature abounds with interesting if not useful papers that misdiagnose MRSA (and other) cutaneous abscesses as recluse bites.  Thus, it is hard to get good data on appropriate treatment as there are so many confounders.  Things that may work for all other necrotic wounds may not work for cutaneous loxoscelism and vice versa. The list of potential treatments is large, and the following list is not all-encompassing:

  • Cold packs
  • Heat packs
  • Electric shock
  • Hyperbarics
  • Nitroglycerin
  • Steroids
  • Surgical excision
  • Symptomatic treatment
  • Dapsone

So what does work? Truthfully, not a lot.  Very little human evidence for any treatments.

Cold packs might help, and heat packs might worsen lesions.  Not a lot of data to this effect, and in one letter to the editor the authors reference their other papers, which doesn’t mention heat or cold at all.

Brown recluse spider bites: Stay cool

Electric shock certainly isn’t helpful in animal studies, but probably is entertaining.  Why every type of envenomation needs a trial of electric shock is beyond me.

Dapsone or electric shock therapy of brown recluse spider envenomation?

Hyperbaric oxygen therapy helps many wounds.  Unclear benefit in humans, in animal studies no benefits were observed. This paper doesn’t have clearly identified spider bites, and has a small sample size.

Brown Recluse Spider Bites: Beneficial Effects of Hyperbaric Oxygen.

Topical nitroglycerin has theoretical benefit of decreased vasoconstriction, but no actual benefit in rabbits. It may actually worsen systemic effects by dispersing venom instead of keeping it localized.

A controlled trial of topical nitroglycerin in a New Zealand white rabbit model of brown recluse spider envenomation.

Steroids don’t decrease ulcer size, but may help with systemic symptoms such as pruritis.

North American Loxoscelism: Necrotic Bite of the Brown Recluse Spider.

Surgical excision helps if done late (like, 6 weeks later), but will cause worsening local effects if done early in the process.

Brown recluse spider bites. A comparison of early surgical excision versus dapsone and delayed surgical excision.

Dapsone is the old standby.  Theoretically prevents PMN infiltration, but in practice is incredibly harmful.  It causes hemolysis in all patients, as well methemoglobinemia to a degree in all, profound in certain patients.  It also has side effects of headaches, GI upset, hepatitis, exfoliative dermatitis, agranulocytosis, and motor neuropathy.  There have also not been any prospective trials on humans with any benefit.  Just don’t use it.


Symptomatic treatment, e.g. antihistamines and analgesics, are probably most effective at what they do, but they don’t do much for ulcers or systemic pathology. Just don’t expect a lot of evidence on their behalf.

So what to do if someone comes in and says they have a brown recluse bite?  If you live in an endemic area, 99 times out of 100 it’s still MRSA.  If you live somewhere they don’t live, which is anywhere east of Tennessee, north of Missouri, or the small region near the Mexican border from Texas to California, it’s always MRSA.  In the off chance you do have an identified spider and a small red lesion, rest assured that it will become necrotic less than 10% of the time.  However, you may want to check a urine as it’s an easy and non-invasive way to check for hemolysis.  While you’re at it, put a cold pack on the area.  And by cold pack I mean ice pack, not the chemical variety.  Beyond that, the evidence for anything is lacking.  Just supportive care.

Along came a spider

Black widow spider bites, while rare enough in the actual world, are often present at ABEM General.  How many know what to do for these patients when they present to the ED?

The most common answer given is IV calcium gluconate. Well, according to Clark et al., the NNT is 25 as only 4% got relieve with that treatment.  Given that it can be caustic to veins, and the benefit is neglible, you probably don’t want to be giving it.
Benzos and opioids are more effective for treatment of the pain and muscle spasm.  Antivenin is even more effective, as well as significantly decreasing length of stay in the hospital.  However, the cost of the antivenom may be more than the cost of hospitalization, so you may want to reserve it for people with other systemic medical problems.  Be wary of the allergic or atopic patient, as the only death in that series was an asthmatic who was given IV push antivenom instead of the usual drip.

“Clinical presentation and treatment of black widow spider envenomation: a review of 163 cases.”

For those that didn’t know, the current equine latrodectus antivenom is so old that it predates the FDA, and thus has grandfathered approval. It does appear significantly safer than the old Wyeth equine crotalid antivenom.

A word about magnesium.  You aren’t a real emergency doctor if you haven’t seen a medical condition and thought, “yeah, a little magnesium could treat that.” Well, the literature is lacking for magnesium, so don’t expect an endorsement here. The only paper I’ve found that I can read (my German and Russian is lacking) isn’t even on pubmed, so you have to look for it.  And then when you read it, you don’t get that part of your life back, as it is a 4 patient case series that shouldn’t be practice changing.

Cesareo DA. 1934. “Red back” spider bite and magnesium sulphate treatment. Am. J. Trop. Med. Hyg. 14:33–44