15.2 Adverse Drug Reactions

Adverse drug reactions in the infusion context

Quick Answer: An adverse drug reaction (ADR) is a harmful or unintended response to a medication at normal doses or during therapeutic use. In infusion nursing, prioritize recognition, severitying severity, stopping the culprit infusion, and escalating for airway/breathing/circulation threats. Anaphylaxis treatment centers on intramuscular epinephrine plus airway support and IV fluids—not antihistamines alone.

Domain 3I.2 sits next to rate-related problems and hazardous-drug safety because many ADRs present during or shortly after parenteral administration. The exam expects more than “call the doctor”: it expects a ordered emergency sequence, correct allergy documentation, and the ability to separate local tissue injury from systemic reaction.

Type I hypersensitivity and anaphylaxis vs anaphylactoid reactions

Type I (IgE-mediated) hypersensitivity

Type I reactions involve antigen cross-linking of IgE on mast cells and basophils with rapid release of histamine and other mediators. Prior sensitization is typical (though patients may not recall a prior mild exposure). Clinical spectrum ranges from urticaria to anaphylaxis.

Anaphylaxis is a severe, potentially fatal, systemic hypersensitivity reaction usually of rapid onset. Clues include:

• Skin/mucosal: urticaria, pruritus, flushing, angioedema
• Respiratory: dyspnea, wheeze, stridor, throat tightness, hypoxia
• Cardiovascular: hypotension, tachycardia, syncope, shock
• Gastrointestinal: crampy pain, vomiting, diarrhea
• Sense of impending doom

Not every feature must be present. Hypotension plus known allergen exposure, or skin findings plus respiratory compromise, should trigger anaphylaxis thinking.

Anaphylactoid (non–IgE-mediated) reactions

Anaphylactoid reactions produce a similar clinical picture through direct mast-cell activation or other non–IgE pathways (examples in concept: some contrast reactions, rapid vancomycin flushing-syndrome physiology, certain opioid histamine effects). From the bedside, severe presentations are treated supportively like anaphylaxis when airway or perfusion is threatened. Mechanism matters later for allergy labeling, skin testing, and rechallenge decisions—but do not withhold epinephrine in a crashing patient because you are debating IgE vs non-IgE.

Cytokine release and delayed reactions

Cytokine-release reactions

Cytokine release (including cytokine release syndrome concepts with some biologics and immunotherapies) may present with fever, chills, rigors, myalgias, hypotension, and capillary leak–type physiology during or after infusion. These are not always classic IgE allergy. Management is protocol-driven: slow or stop the infusion, supportive care, antipyretics, fluids, and sometimes corticosteroids or other ordered therapies per specialty pathway. Know that first doses and dose escalations are higher-risk windows for many biologics.

Delayed reactions

Not all ADRs are immediate. Delayed hypersensitivities (e.g., delayed maculopapular rashes, some severe cutaneous adverse reactions, serum sickness–like patterns) may appear hours to days later. Nursing implications: teach patients what to report after discharge, document timed onset carefully, and do not restart the agent without provider/allergy guidance. Delayed severe cutaneous reactions (e.g., concepts of SJS/TEN) are emergencies requiring immediate drug cessation and specialty care—exam stems may test “stop and escalate,” not home antihistamine alone.

Grading: mild, moderate, severe

Use a practical severity frame (facility infusion-reaction scales may be more granular):

Grading drives decisions. Mild isolated itching is not managed the same as stridor and hypotension. Document grade language your facility uses so the next clinician understands severity.

Anaphylaxis emergency pathway (high-yield sequence)

When anaphylaxis is suspected during an infusion:

1. STOP the drug/infusion immediately. Do not leave the culprit running “a little longer.”
2. Call for help / activate rapid response or code per severity and setting.
3. Maintain airway; high-flow oxygen as indicated; prepare for advanced airway if obstruction evolves.
4. Epinephrine IM (anterolateral thigh preferred conceptually) is first-line for anaphylaxis—do not delay for IV start, steroids, or antihistamines.
5. Place patient supine (or position for comfort/respiration); elevate legs if hypotensive and no respiratory contraindication per emergency guidance.
6. Establish/maintain IV access and infuse 0.9% sodium chloride for hypotension as ordered/protocol.
7. Remove other ongoing allergens if identifiable; monitor continuously (SpO2, BP, HR, mentation).
8. Adjuncts after epinephrine as ordered: antihistamines, bronchodilators, corticosteroids—these are adjuncts, not substitutes for epinephrine in true anaphylaxis.
9. Observe for biphasic recurrence; admit/observe per protocol even if early improvement occurs.
10. Document and update allergy records before the next shift administers the same agent.

Exam traps for anaphylaxis

• Giving diphenhydramine first and “watching” while the patient is hypotensive and wheezing
• Leaving the infusion at a “keep-open” rate of the same drug
• Confusing mild vancomycin flushing syndrome with full anaphylaxis—or the reverse: dismissing hypotension and stridor as “just flushing syndrome”
• Forgetting IM epinephrine route concepts in favor of slow IV push epinephrine without emergency indication/protocol

Documentation, allergy labeling, and rechallenge

Documentation must capture: drug name and dose, lot if relevant, route and rate, exact time of onset, signs/symptoms by system, interventions and times, patient response, notifications, and teaching. Vague notes (“had a reaction”) fail the next caregiver.

Allergy labeling in the EHR and medication administration record should reflect the agent, reaction type/severity when known, and date. Distinguish true allergy from intolerance (e.g., nausea alone) when the history supports it—but when anaphylaxis occurred, label clearly to prevent re-exposure.

Rechallenge (including desensitization) is not a bedside improvisation. It occurs only under controlled protocols—often allergy/immunology or specialty order sets—in settings prepared for anaphylaxis. Home or casual unit rechallenge after severe reaction is an exam wrong answer.

Distinguishing extravasation (local) from systemic ADR

This distinction is a CRNI favorite because both can present “during the IV med.”

Both require stopping the infusion. After stop, branch: tissue pathway vs systemic emergency pathway. Some patients can have both (e.g., allergic reaction plus a bad site)—treat the life threat first while protecting tissue.

Prevention and readiness

• Allergy history before high-risk infusions; reconcile EHR allergies
• First-dose monitoring policies for agents with known reaction risk
• Bedside emergency equipment: oxygen, suction, epinephrine, airway tools, IV fluids
• Know which infusions need premedication per protocol (not as a substitute for rate control or true allergy avoidance)
• Educate patients to report itching, throat tightness, dyspnea, or dizziness immediately

Master the mental model: classify the reaction → grade severity → stop the drug → treat anaphylaxis with epinephrine-first care when indicated → document and label → rechallenge only under protocol → never confuse local extravasation with systemic ADR. That model converts chaotic bedside events into defensible CRNI answers.