Pharm Basics

Side Effects vs. Adverse Reactions

Pharmacology Basics

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All drugs can produce effects beyond their intended action. Knowing the difference between an expected side effect and a true adverse reaction is critical.

Side Effect
Adverse Drug Reaction (ADR)
Predictability
Predictable, dose-related
Often unpredictable
Severity
Usually mild
Can be severe or life-threatening
Action
Manage symptomatically — usually continue drug
Often requires stopping the drug
Example
Drowsiness from diphenhydramine
Stevens–Johnson syndrome from sulfonamides

Anaphylaxis — Emergency

Recognize

  • Hives, flushing, itching
  • Wheezing, stridor, throat tightness
  • Facial / tongue swelling (angioedema)
  • Hypotension, tachycardia
  • Nausea, vomiting, dizziness

Respond

  1. 1STOP the drug immediately
  2. 2Call for help / activate rapid response
  3. 3Maintain airway — give oxygen
  4. 4Administer IM epinephrine 0.3–0.5 mg (anterolateral thigh)
  5. 5IV fluids for hypotension
  6. 6Adjuncts: antihistamines, corticosteroids, bronchodilators
  7. 7Document and update allergy list

Types of Adverse Reactions

Allergic

Immune-mediated; ranges from rash to anaphylaxis (penicillin allergy)

Idiosyncratic

Genetically determined, unpredictable response (G6PD hemolysis)

Toxic

Dose-dependent organ damage (acetaminophen → liver failure)

Teratogenic

Fetal harm (warfarin, ACE inhibitors, isotretinoin)

Key Pearls

  • Always assess allergies BEFORE administration — document the reaction type
  • GI upset is intolerance, NOT a true allergy
  • Penicillin and cephalosporin cross-reactivity ~1–10%
  • Black-box warnings = FDA's most serious safety alerts

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.