What to do after an injection of unknown medication?

Management After Injection of Unknown Medication

Immediately assess for signs of anaphylaxis or severe infusion reaction, establish IV access with normal saline, monitor vital signs continuously, and prepare emergency equipment including epinephrine—most life-threatening reactions occur within the first 30 minutes but can be delayed up to 24 hours. 1

Immediate Assessment (First 5-15 Minutes)

Evaluate the ABCs (airway, breathing, circulation) and level of consciousness immediately. 1

Critical Signs Requiring Emergency Intervention

Monitor for anaphylaxis criteria—any ONE of the following constitutes anaphylaxis requiring immediate epinephrine 1:

• Acute onset with skin/mucosal involvement (hives, flushing, angioedema) PLUS respiratory compromise (dyspnea, wheeze, stridor) OR hypotension 1
• Two or more organ systems involved rapidly after exposure: skin-mucosal changes, respiratory compromise, hypotension, or persistent gastrointestinal symptoms 1
• Hypotension alone after known allergen exposure 1

Vital Signs and Positioning

• Position patient in Trendelenburg if hypotensive, sitting upright if respiratory distress, or recovery position if unconscious 1
• Maintain IV access with normal saline running—do NOT remove the line 1
• Administer oxygen if oxygen saturation <94% or respiratory distress present 1

Emergency Treatment Protocol

For Confirmed Anaphylaxis (Grade 3-4 Reaction)

Administer epinephrine 0.01 mg/kg (maximum 0.5 mg of 1:1000 dilution) intramuscularly into the lateral thigh immediately—this is the single most critical intervention. 1

• Repeat epinephrine every 5-15 minutes if inadequate response 1
• Begin rapid fluid resuscitation with 1-2 liters normal saline at 5-10 mL/kg in first 5 minutes, followed by 20 mL/kg boluses 1
• Administer combined H1 and H2 antihistamines: diphenhydramine 25-50 mg IV slowly PLUS ranitidine 50 mg IV over 5 minutes 1
• Give corticosteroids (methylprednisolone 1-2 mg/kg IV or equivalent) to prevent biphasic reactions, though not critical for acute management 1

For Mild-Moderate Reactions (Grade 1-2)

Stop or slow the infusion immediately if medication is still being administered 1, 2:

• Provide symptomatic treatment: acetaminophen 650-1000 mg for fever, diphenhydramine 25-50 mg for pruritus/urticaria 2
• Monitor vital signs every 5-15 minutes for progression 2
• Most mild reactions are self-limiting and resolve within 15-30 minutes 2

Observation Period and Delayed Reactions

All patients must be observed for minimum 30 minutes after any injection, but extend to 1-2 hours if any symptoms occurred. 1, 2

Critical Timeframes

• 77% of severe reactions occur during first exposure, but reactions can occur at any time 2
• 38% of systemic reactions occur 30 minutes to 6 hours after injection 1
• Biphasic reactions (recurrence after initial resolution) occur in 10-23% of cases, typically within 2-24 hours 1

Post-Discharge Instructions

Educate patient about delayed reaction symptoms that can occur up to 24 hours post-injection 2:

• Flu-like symptoms, fever, arthralgias, myalgias 2
• Instruct patient to return immediately or call 911 for: difficulty breathing, chest tightness, severe rash/hives, dizziness, or swelling of face/throat 1
• Consider prescribing epinephrine auto-injector for high-risk patients to carry for 24-48 hours 1

Special Considerations Based on Injection Type

If Accidental Epinephrine Injection (e.g., into digit)

Accidental epinephrine injection into fingers/toes causes vasoconstriction and potential necrosis—treat immediately with warming, topical nitroglycerin cream, or locally injected phentolamine. 1

If Suspected Contaminated Injection

Assess for signs of infection: redness, swelling, tenderness at injection site 3:

• 48% of people who inject drugs develop injection site infections with redness, swelling, and tenderness 3
• Initiate antibiotics if cellulitis, abscess, or systemic signs of infection present 3
• Educate about seeking care early—44-45% delay seeking treatment ≥5 days, increasing morbidity 3

If Opioid Overdose Suspected

Administer naloxone 0.4-2 mg IV/IM/SC immediately if respiratory depression, decreased consciousness, or pinpoint pupils present 4:

• Repeat every 2-3 minutes if no response, up to 10 mg total 4
• If no response after 10 mg, question opioid-induced toxicity diagnosis 4
• Duration of naloxone (30-90 minutes) is shorter than many opioids—repeated doses or continuous infusion may be required 4

Documentation and Reporting Requirements

Document the following immediately 1, 5:

• Exact time of injection and symptom onset 1
• Description of medication if known (appearance, color, source) 1
• All vital signs and physical examination findings 1
• Treatment administered and patient response 1

If unsafe injection practice identified (syringe reuse, medication mishandling), facility leadership must be notified immediately for potential patient notification event. 5

Prevention of Future Events

Verify medication labels before EVERY injection to avoid wrong medication errors 1:

• Never reuse syringes or needles between patients—this accounts for 66,748 patient notification events from 2012-2018 5
• Clean injection ports with alcohol for 15-30 seconds using friction before accessing 1
• Discard used syringes immediately after use—never leave in drug trays with other equipment 1

Common Pitfalls to Avoid

• Do NOT delay epinephrine administration while waiting for IV access—give IM immediately if anaphylaxis suspected 1
• Do NOT discharge patients before 30-minute observation period, even if asymptomatic 1
• Do NOT assume mild initial symptoms will remain mild—rapid progression to severe anaphylaxis can occur within minutes 1
• Do NOT treat bradycardia in anaphylaxis with epinephrine alone—give atropine 600 mcg IV 1
• Do NOT use beta-blockers in patients receiving allergen immunotherapy—increases risk of treatment-resistant anaphylaxis 1