Anti-venom shortage for black widow spider bites may be ending

Publish date: 2024-07-13

Amid the worsening nationwide shortage of an estimated 300 drugs is a longtime one for a rare, but extremely painful, bite — that of the black widow spider.

The anti-venom pain-relieving drug Antivenin (Latrodectus mactans) is not commonly used, making it less impactful than the other shortages, yet “it is extremely concerning for someone who would benefit from the treatment,” said Michael Ganio, senior director of pharmacy practice and quality at the American Society of Health-System Pharmacists. Still, “that doesn’t mean patients should panic,” he said.

Merck, the company that makes Antivenin, now says that the drug is available and that it has “taken a number of steps to ensure uninterrupted supply.” Merck sells only between 300 to 800 vials of Antivenin each year.

The drug is made by injecting horses with the venom, then extracting antibodies the animals produce, and it should not be given to anyone with an allergy to horses.

Black widow spiders — so named because the females sometimes devour their partners after mating — are the creepy stuff of the imagination and pop culture. The menacing hype, however, doesn’t match the reality.

Their bite can become extremely painful, but it’s almost never fatal.

“Black widows freak people out — they are the queens of spider terror — and an endless source of fascination,” said Kurt Kleinschmidt, a toxicologist and professor of emergency medicine at UT Southwestern Medical Center. “But the truth is that while they can cause a lot of misery, they’re very unlikely to kill you.”

Creepy, but eco-friendly, spiders

The black widow spider, distinguished by the red hourglass pattern on its abdomen, is among the most feared venomous spiders in the United States and is found throughout North America, including the Mid-Atlantic region, but especially in the South and West.

They most often live in dark places, in woodpiles, under eaves or fences, in garages and outdoor toilets, and in areas with considerable debris. They are considered eco-friendly because they eat pests and other insects that harm plants.

“They generally stay outdoors and are very helpful around a community to assist in eating flies and mosquitoes that may be in the environment,” said Richard Clark, director of toxicology at the University of California at San Diego.

They usually bite humans in self-defense — when they feel threatened — and leave two characteristic puncture marks in the skin. They secrete a neurotoxin that can produce localized discomfort or can spread to the chest, abdomen, even the entire body, causing more severe pain.

There were about 1,000 reported bites in 2021, roughly half of them treated in health-care facilities, according to the annual report of the National Poison Data System. The number increased to 1,137 in 2022, said Shireen Banerji, director of the Rocky Mountain Poison Center and clinical assistant professor of clinical pharmacy at the University of Colorado, who took last year’s statistics from the NPDS database.

“That number is not huge, but if you are bitten and you are in agony, then the shortage is a real problem,” she said. “We have been challenged with this anti-venom shortage intermittently for years.”

Black widow spider bites are infrequent in the area covered by the National Capital Poison Center, which includes D.C., Northern Virginia, and Montgomery and Prince Georges’ counties in Maryland.

Since 2013, there have been 139 reported bites, and none required the use of anti-venom, said Kelly Johnson-Arbor, a medical toxicologist and co-director of the center, who stressed their rarity. “In almost 20 years of practicing medical toxicology, I have not taken care of a patient with a black widow spider bite,” she said.

Symptoms of a bite

Black widow bites can range from uncomfortable to excruciatingly painful, experts said.

If someone gets “a lot of venom, they can have a large amount of pain all over their body, in your muscles, your chest and your abdomen,” said Daniel Colby, an emergency medicine physician at UC Davis Health.

The symptoms, experts said, can include:

Moderate to severe pain
Sweating around the bite
Mild redness to a targetlike appearance
Central blanching with a redder ring around bite site
Painful cramping that may travel to the chest, back or abdomen
Twitching of muscles near the bite site
Elevated blood pressure and heart rate, vomiting and headache in extreme cases

Sometimes the pain is misdiagnosed if the patient doesn’t realize they have been bitten, Banerji said.

Treatment for a black widow spider bite

Call the national poison control hotline at 1-800-222-1222 if you are bitten for an assessment of the bite and guidance about what to do and whether to head to an emergency room.

“I recommend cleaning the area of the bite, even though infections are not common after their bites,” Clark said. “If there is pain, use over-the-counter analgesics like acetaminophen or ibuprofen.”

Don’t try to catch the spider that bit you. “Leave it alone,” Colby said.

Pain usually starts within several hours. If the medications don’t help, go to an urgent care or hospital emergency department, Clark said. “For the most part, bites by black widows are not fatal and, even in the worst situations, lead to severe pain for one to two days,” he said.

How and when to use the anti-venom

The first line of treatment in a hospital emergency setting should always be pain medication and — if there are muscle spasms — muscle relaxers, experts said. Anti-venom — administered intravenously — should be used only when other medications fail and the pain is unbearable, they said. Even then, clinicians should be very cautious because life-threatening allergic reactions can occur.

“Some think you should go straight to the anti-venom because it works very well, and patients look and feel better sooner,” said S. Rutherfoord Rose, professor of emergency medicine at Virginia Commonwealth University and director of the Virginia Poison Center. “But people like me think you can safely manage most cases with muscle relaxers and pain medication, and not give the anti-venom.”

Kleinschmidt said he has never used the anti-venom. “People have died after receiving it,” he said. “The question is: what’s more dangerous? The bite or the treatment? In terms of pain, the anti-venom has been helpful, but you generally don’t die from pain.”

The reports about the shortage have provoked needless worry, but “for almost all Black Widow” poisonings “in the United States, the risk of anti-venom treatment outweighs the potential benefit most of the time,” said Aaron Skolnik, an emergency room physician at the Mayo Clinic in Phoenix.

Most hospitals don’t even routinely stock it, although Merck has supplied it in the past in emergencies, said James Leonard, director of clinical services at the Maryland Poison Center and associate professor at the University of Maryland School of Pharmacy. “We had a patient a few years ago who wasn’t responding, so we asked the company for it and got it fairly quickly,” he said. “We ended up not using it because the patient started getting better — and the company asked for it back.”

The drug is safe and effective, but it should be used with care, Clark said. It comes with a skin test for allergies, but it is not “100 percent predictive of a reaction,” he said. Anyone with a horse allergy probably shouldn’t receive it, and “caution should probably also be used before giving it to someone with a history of asthma or allergies to a lot of other environmental things,” he said.

The best way to prevent a bite

Experts suggested these precautions:

Know where the spiders hang out.
Don’t reach where you can’t see.
Wear gloves, especially when carrying wood from a woodpile.
“If you leave your gardening shoes in the tool shed, turn them over, tap on them, and look inside before you put them on,” Rose said.

“We can coexist with them,” he said, “but when you are in their environment — be careful.”

correction

An earlier version of this article said that the black widow spider was one of two venomous spiders in the United States. It is among several venomous spiders in the United States. This version has been corrected.