Spider Bite (Black Widow)MANAGEMENT

ENVIRONMENTAL AND EXPOSURE PRESENTATIONS · 12 SECTIONS

⚲

649 items

☷ Legend

⚲

Cardiovascular Presentations71▾

Respiratory Presentations52▾

Neurological Presentations83▾

Gastrointestinal Presentations74▾

Genitourinary and Reproductive Presentations48▾

Infectious Disease Presentations148▾

Trauma Presentations89▾

Toxicologic Presentations80▾

Psychiatric Presentations26▾

Musculoskeletal and Rheumatologic Presentations96▾

Dermatology Presentations23▾

Environmental and Exposure Presentations27▾

Acute Mountain Sickness Arterial Gas Embolism Bee-Wasp Sting (Anaphylaxis)Chilblains Ciguatera Fish Poisoning Coral Cut Decompression Sickness Electrical Burn Injury Envenomation (snake, spider, insect)High Altitude Cerebral Edema (HACE)High Altitude Pulmonary Edema (HAPE)High-altitude illness Hypothermia Hypothermia (Mild)Hypothermia (Severe)Immersion Foot Lightning Strike Injury Scombroid Fish Poisoning Scorpion Envenomation Sea Urchin Injury Shark Bite Snake Envenomation Spider Bite (Black Widow)Spider Bite (Brown Recluse)Stingray Spine Injury Tick paralysis White Phosphorus Burn

Hematologic and Oncologic Presentations36▾

Pediatric-Specific Presentations19▾

Endocrine and Metabolic Presentations45▾

ENT and Maxillofacial Presentations27▾

Ophthalmologic Presentations19▾

Obstetric Presentations23▾

Systemic and Miscellaneous Presentations17▾

01Approach to the Critical Patient/attcp59

Immediate priorities

›Airway and breathing assessment

›Respiratory distress in severe envenomation (Grade 3)

›Children and elderly at highest risk

›Accessory muscle use

›If respiratory compromise, escalate to resuscitation bay

›Supplemental oxygen titration

›Prepare for airway intervention if deteriorating

›Cardiovascular threats

›Hypertensive urgency or emergency

›SBP > 180 mmHg with end organ symptoms

›Chest pain with ECG changes

›Cardiac involvement indicators

›Myocarditis with arrhythmia

›Takotsubo-like cardiomyopathy

›Pulmonary edema

›If hemodynamic instability, initiate continuous cardiac monitoring and IV access

›12-lead ECG for chest pain

›Troponin sampling

›Envenomation severity grading

›Grade 1 — local pain only

›No systemic symptoms

›Bite site findings only

›Grade 2 — regional pain and mild systemic features

›Back or abdominal cramping

›Diaphoresis limited to bite region

›Grade 3 — generalized pain, autonomic instability, abnormal vitals

›Hypertension and tachycardia

02History/hx58

Bite circumstances

›Exposure context

›Outdoor activity in shady enclosed spaces

›Woodpiles and sheds

›Rock piles and yard debris

›Gardening equipment and outdoor toilets

›Time of bite and elapsed time since envenomation

›Symptom onset relative to bite time

›Progression rate

›Spider identification

›Shiny black body with ventral red hourglass marking

›Markings may be absent or atypical in some species (L. hesperus)

›Bring spider specimen if safely captured

Symptom characterization

›Pain pattern

›Initial pinprick sensation at bite site

›Proximal migration over minutes to hours

›Crampy and spasmodic quality

›Generalized distribution

›Abdominal pain — most common chief complaint

›Back and leg pain

›Chest tightness

›Wave-like pattern continuing 48 to 72 hours

›Intermittent escalation

›Gradual resolution with treatment

›Autonomic symptoms

›Diaphoresis pattern

›Localized to bite site

03Physical Exam/exam58

Vital signs

›Hemodynamic snapshot

›Blood pressure

›Hypertension hallmark of Grade 3 envenomation

›SBP > 180 mmHg triggers urgent management

›Heart rate

›Tachycardia associated with severe envenomation

›Bradycardia unusual, raises alternative diagnosis

›Temperature

›Afebrile in uncomplicated latrodectism

›Fever raises concern for superinfection or alternative diagnosis

›Respiratory rate

›Elevated in severe chest wall rigidity

›Children: respiratory distress triggers escalation

Skin and bite site

›Local findings

›Bite site appearance

›Solitary papule or puncture wound

›Target lesion with central erythema

›Local erythema possible

›Absence of necrosis

›Distinguishes from brown recluse (Loxosceles) bite

›No spreading skin breakdown or eschar

›Diaphoresis distribution pattern

›Pathognomonic asymmetric or localized sweating

›Below-knee bilateral pattern distinctive

Musculoskeletal and abdominal exam

›Muscle rigidity findings

04Differential Diagnosis/ddx49

Life-threatening mimics

›Cardiovascular emergencies

›Acute coronary syndrome

›ICD-10 I24.9

›Chest pain with hypertension and tachycardia overlap

›ECG and troponin differentiate

›Hypertensive emergency

›ICD-10 I16.1

›Elevated BP with end organ damage

›Exposure history and rigidity absent

›Takotsubo cardiomyopathy

›Stress-triggered LV dysfunction

›Increasingly recognized complication of Latrodectus envenomation

›Abdominal emergencies

›Acute peritonitis

›ICD-10 K65.9

›True rebound tenderness and absent bowel sounds distinguish

›CT abdomen may be needed when diagnosis uncertain

›Ruptured ectopic pregnancy

›Peritoneal signs and hemodynamic instability

›Beta-hCG in reproductive-age females

Toxicologic and infectious mimics

›Toxidromes

›Organophosphate poisoning

›Cholinergic toxidrome: SLUDGE and DUMBELS

›Miosis and bronchorrhea distinguish

›Serotonin syndrome

›Muscle rigidity, autonomic instability, diaphoresis overlap

05Laboratory Tests/lt40

Core labs

›Cardiac evaluation

›Troponin I or T

›Indicated for chest pain or suspected cardiac involvement

›Myocarditis and demand ischemia screen

›Serial measurement at 0 and 3 hours if initial negative

›CK and CK-MB

›Rhabdomyolysis screen in severe envenomation

›Myocardial injury marker adjunct

›12-lead ECG

›Arrhythmia detection

›ST and T-wave changes in myocarditis

Metabolic and renal labs

›Renal function panel

›Creatinine and BUN

›Baseline renal function

›Rhabdomyolysis-associated AKI risk

›Electrolytes

›Sodium and potassium in severe diaphoresis or vomiting

›Calcium and magnesium not useful for guiding treatment

›Glucose

›Adrenergic excess can elevate blood glucose

›Muscle injury markers

›CK (creatine kinase)

›Elevation supports rhabdomyolysis diagnosis

›Threshold for IV fluids: CK > 1000 U/L in symptomatic patient

›Urinalysis

›Myoglobinuria (tea-colored urine)

06Diagnostic Tests/dt65

Scoring Systems

›Envenomation severity grading

›Grade 1 (mild)

›Local pain at bite site

›No systemic symptoms

›Normal vital signs

›Grade 2 (moderate)

›Regional muscular pain

›Diaphoresis limited to bite area

›Vital signs near normal

›Grade 3 (severe)

›Generalized muscular pain (back, abdomen, chest)

›Diaphoresis remote from bite site

›Hypertension or tachycardia

›Grade 3 is the primary trigger for antivenom consideration

›Clinical decision framework

›No validated point scoring system exists for latrodectism

›Grading system is descriptive, not point-based

›Clinical trajectory and response to analgesia guide management

›Poison control severity assessment

›Integrate poison control guidance for antivenom eligibility

›ACEP Level C recommendation for grading-guided antivenom use

MRI

›MRI role in latrodectism

›Not routinely indicated for spider envenomation

›Diagnosis is clinical

›No neuroimaging finding pathognomonic for latrodectism

›MRI brain indications

07Disposition/dispo44

Admission indications

›Inpatient admission criteria

›Grade 3 envenomation

›Generalized pain and autonomic instability

›Abnormal vital signs

›Cardiac involvement

›Troponin elevation

›ECG changes or arrhythmia

›Pulmonary edema

›Antivenom administration

›Post-antivenom monitoring for 4 to 6 hours minimum

›Anaphylaxis risk and delayed serum sickness monitoring

›Extremes of age with any systemic symptoms

›Children under 5 years

›Elderly with cardiovascular comorbidities

›Rhabdomyolysis with AKI

›IV hydration and monitoring requirement

ICU indications

›Critical care level criteria

›Hypertensive emergency with end organ damage

›Encephalopathy or stroke symptoms

›Acute pulmonary edema

›Hemodynamic instability

›Shock physiology requiring vasopressors

›Cardiogenic shock from myocarditis

›Respiratory failure

›Children with chest wall rigidity and respiratory compromise

›Intubation required

08Treatment/t94

Supportive care and analgesia

›Grade 1 management

›Local wound care

›Wound cleansing with soap and water

›Tetanus prophylaxis if not up to date

›Oral analgesia

›Ibuprofen 400 to 600 mg PO every 6 to 8 hours

›With food to reduce GI risk

›Avoid if renal impairment or pregnancy

›Acetaminophen 650 to 1000 mg PO every 6 hours

›Maximum 4 g per day

›Hepatic dose adjustment when indicated

›Grade 2 to 3 parenteral analgesia

›Opioid analgesia

›Morphine 0.1 mg/kg IV or 4 to 8 mg IV in adults

›Titrate every 15 to 30 minutes to pain control

›Monitor respiratory status

›Hydromorphone 0.015 mg/kg IV as alternative

›1 to 2 mg IV in adults

›Reassess in 15 to 30 minutes

›Antiemetics for nausea and vomiting

›Ondansetron 4 mg IV every 6 hours PRN

›QT prolongation review in cardiac involvement

›Metoclopramide 10 mg IV as alternative

Muscle spasm management

›Benzodiazepines

›Diazepam IV or PO

›Diazepam 5 to 10 mg IV for acute muscle spasm

›Repeat every 15 to 30 minutes as needed

›Maximum 30 mg in adults

›Diazepam 5 to 10 mg PO for mild to moderate spasm

›Sedation risk in elderly

›Lorazepam alternative

›1 to 2 mg IV every 4 to 6 hours

›Shorter duration of action than diazepam

›No demonstrated superiority in clinical trials

›Evidence basis

›No RCT data support benzodiazepines for latrodectism muscle spasm

›Anecdotal and observational benefit reported

›ACEP Level C recommendation

›Agents not recommended

›Calcium gluconate — no demonstrated benefit

›Previously used but shown ineffective in controlled studies

›Not recommended by current guidelines

›Magnesium sulfate — no demonstrated benefit

›Anecdotal reports only

›Not part of standard care

Antivenom

›Antivenin Latrodectus mactans (equine-derived)

›Indications

›Grade 3 envenomation refractory to opioids and benzodiazepines

›Persistent generalized pain

›Autonomic instability unresponsive to supportive care

›Extremes of age with moderate to severe symptoms

›Children under 5 years

›Elderly with cardiovascular comorbidities

›Pregnancy with severe envenomation

›Cardiac complication (myocarditis, arrhythmia)

›Dosing

›One vial (2.5 mL) IV in 50 to 100 mL normal saline over 15 to 30 minutes

›Second vial if symptoms persist after 30 to 60 minutes

›Dilution reduces anaphylaxis risk

›IM route no longer preferred — IV preferred for predictable absorption

›Pre-treatment

›Skin testing historically recommended but now discouraged

›Skin testing does not reliably predict anaphylaxis

›Have epinephrine 0.3 mg IM immediately available

›Pre-medication with diphenhydramine 25 to 50 mg IV

›Reduces minor hypersensitivity reactions

›Efficacy

›RCT of purified F(ab')2 antivenom demonstrated reduced treatment failures vs. placebo

›No serious drug-related adverse events in RCT

›Symptom relief typically within 30 to 60 minutes of IV administration

›Adverse effects

›Anaphylaxis risk up to 5%

›Immediate hypersensitivity reaction with urticaria, bronchospasm, hypotension

›Epinephrine treatment and resuscitation preparation required

›Delayed serum sickness

›Onset 7 to 21 days after antivenom

›Fever, urticaria, arthralgias, lymphadenopathy

›Treat with corticosteroids and antihistamines

›Availability

›Limited availability in the United States

›Contact poison control center for sourcing and indication guidance

Hypertension management

›Antihypertensive strategy

›Calcium channel blockers

›Amlodipine 5 mg PO for moderate hypertension

›Onset 1 to 2 hours

›Does not treat underlying spasm mechanism

›Nifedipine 10 mg PO short-acting for urgent lowering

›Hydralazine IV for acute severe hypertension

›10 to 20 mg IV every 20 to 30 minutes

›Titrate to SBP < 160 mmHg

›Reflex tachycardia possible

›Antivenom is the definitive treatment for autonomic-driven hypertension

›Antihypertensives are temporizing

›Reassess need after antivenom administration

09Special Populations/sp64

Pregnancy

›Pregnancy-specific considerations

›Envenomation risk profile

›Severe envenomation has been associated with preterm labor

›Uterine contractions may be triggered by autonomic excess

›Antivenom use in pregnancy

›Antivenom recommended for Grade 3 envenomation in pregnancy

›Benefits outweigh risk of anaphylaxis in severe cases

›Equine-derived antivenom crosses placenta minimally

›Fetal monitoring initiated after administration

›Analgesic considerations

›Opioids: morphine or hydromorphone IV acceptable acutely

›Neonatal respiratory depression risk with near-term exposure

›NSAIDs avoided after 30 weeks gestation

›Premature closure of ductus arteriosus risk

›Benzodiazepines: use with caution

›Neonatal sedation and withdrawal risk

›Obstetric consultation

›Indicated for Grade 2 to 3 envenomation in viable pregnancy

›Continuous fetal monitoring when gestation > 24 weeks

Geriatric

›Older adult considerations

›Higher severity risk

›Cardiovascular comorbidities amplify cardiac complication risk

›Myocarditis, Takotsubo, and arrhythmia more common

›Analgesic dosing adjustments

›Morphine: start at lower doses (2 to 4 mg IV)

›Increased sensitivity to opioid CNS and respiratory effects

10Background/b58

Epidemiology

›Frequency and distribution

›More than 2500 Latrodectus-related poison control calls annually in the United States

›Mortality rare with modern supportive care

›Fatal cases predominantly involve children, elderly, or untreated cardiac complications

›Five Latrodectus widow species found in the United States

›L. mactans (southern black widow) — most common

›L. hesperus (western black widow) — western US

›L. variolus, L. geometricus, L. bishopi

›Geographic distribution expanding northward

›Climate change associated range shift

›Demographics

›58% of reported cases involve males

›Peak exposure in summer and early fall (September peak)

›Occupational exposure: agricultural, construction, military

Pathophysiology

›Mechanism of toxicity

›Alpha-latrotoxin — primary venom component

›Binds presynaptic neurexin and CIRL receptors

›Forms cation pore in presynaptic membrane

›Massive exocytosis of neurotransmitter vesicles

›Neurotransmitter release

›Excess acetylcholine release at neuromuscular junction

›Sustained muscle contraction and spasm

›Fasciculations and rigidity

›Excess norepinephrine and catecholamine release

›Hypertension and tachycardia

›Diaphoresis

11Patient Discharge Instructions/pdi33

copy discharge instructions

›Spider bite home care instructions

›Keep bite site clean and dry

›Wash gently with soap and water daily

›Watch for signs of infection (increasing redness, warmth, swelling, pus)

›Take medications as prescribed

›Ibuprofen or acetaminophen for pain relief

›Take with food to avoid stomach upset

›Rest and hydration

›Drink plenty of fluids especially if you were sweating heavily

›Avoid strenuous activity for 48 hours

›Warning signs — return to emergency department immediately

›Return to ER if any of the following develop

›Severe cramping pain in abdomen, back, or chest

›Profuse sweating spreading to whole body

›Shortness of breath or difficulty breathing

›Racing or irregular heartbeat

›Nausea or vomiting that prevents keeping fluids down

›Muscle stiffness or weakness getting worse

›Swelling around eyes or facial changes

›Symptoms not improving after 24 hours

›Follow up instructions

›Primary care or clinic follow up within 48 to 72 hours

›Review wound healing

›Review any lab results if obtained

›If antivenom was given, watch for delayed reaction

›Fever, rash, joint pain, or swollen glands 7 to 21 days after treatment

›Return to ER or contact physician promptly if these occur

12References/r27

Guidelines and key sources

›Primary guidelines and reviews

›American Family Physician review on spider bites and envenomation management

›Grading system for latrodectism (Grade 1 to 3)

›Antivenom indications and dosing

›The Lancet clinical review on latrodectism

›Pathophysiology and clinical features

›International treatment perspectives

›Annals of Pharmacotherapy epidemiologic data

›US poison center call rates and demographic analysis

›Evidence sources

›RCT of purified F(ab')2 antivenom (Anavip) for latrodectism

›Reduced treatment failures vs. placebo

›No serious antivenom-related adverse events

›Military Medicine case series

›Occupational exposure and rhabdomyolysis reports

›American Journal of Emergency Medicine

›Cardiac complications including Takotsubo-like cardiomyopathy

›Toxicon and Emergency Medicine case reports

›Latrodectus facies and pediatric presentations

›Coding references

›ICD-10 coding

›T63.311A Toxic effect of venom of black widow spider, initial encounter

›T63.312A Toxic effect of venom of other spider, initial encounter

›ICD-10 Z77.098 Contact with venomous arthropods

›SNOMED CT

›Latrodectism disorder concept

›Spider envenomation clinical finding

Learn More: Spider Bite (Black Widow)→

Comprehensive Clinical Review

Structured, evidence-informed, long-form analysis for deeper understanding.

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed August 18, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.