Internal Medicine · Year 3 · from Internal Medicine

Case 3: Drug Fever

Patient Presentation

A 38-year-old woman was admitted 8 days ago for community-acquired pneumonia and was started on ceftriaxone and azithromycin. Her pneumonia clinically improved, and she has been afebrile since day 3. On day 7, she developed a new fever to 38.6°C despite resolution of her respiratory symptoms. She feels well otherwise and denies new symptoms.

Vital Signs

  • Blood Pressure: 118/72 mmHg
  • Heart Rate: 78 bpm
  • Respiratory Rate: 14/min
  • Oxygen Saturation: 98% on room air
  • Temperature: 38.7°C

Physical Examination

  • General: Comfortable, appears well
  • HEENT: Clear oropharynx
  • Cardiovascular: Regular rhythm, no murmurs
  • Pulmonary: Clear to auscultation, improved from admission
  • Abdomen: Soft, non-tender
  • Skin: Faint maculopapular rash on trunk
  • Extremities: No edema, IV site without erythema

Initial Workup

  • CBC: WBC 9,800/μL with 8% eosinophils (elevated)
  • BMP: Normal
  • Repeat chest X-ray: Improved infiltrate
  • Blood cultures: No growth (drawn day 7)
  • Urinalysis: Normal

Clinical Image

Figure 3: Maculopapular drug eruption, commonly associated with beta-lactam antibiotics and often accompanying drug fever.

Image Source: Educational illustration for teaching purposes.

Questions

  1. What clinical features suggest drug fever?
  • A) High fever, rigors, elevated WBC
  • B) Relative bradycardia, eosinophilia, rash, patient appears well
  • C) Fever immediately after drug administration
  • D) Fever with hypotension and altered mental status
  1. Which medication class is most commonly associated with drug fever?
  • A) Fluoroquinolones
  • B) Beta-lactam antibiotics
  • C) Macrolides
  • D) Aminoglycosides
  1. What is the typical time course for development of drug fever?
  • A) Within hours of first dose
  • B) 7-10 days after starting medication (or earlier with re-exposure)
  • C) After completing the full course
  • D) Only with intravenous medications
  1. What is the most appropriate management?
  1. How quickly should fever resolve after discontinuing the offending agent?

Answers

  1. B) Relative bradycardia, eosinophilia, rash, patient appears well - Drug fever classically presents with a patient who "looks too good for their fever." Relative bradycardia, peripheral eosinophilia, and concurrent rash are supportive findings.
  1. B) Beta-lactam antibiotics - Beta-lactams (penicillins, cephalosporins) are the most common cause of drug fever. Other common culprits include sulfonamides, anticonvulsants, and allopurinol.
  1. B) 7-10 days after starting medication (or earlier with re-exposure) - Drug fever typically develops 7-10 days after initiation of a new medication. With prior sensitization, fever can develop within hours of re-exposure.
  1. Management:
  • Discontinue the suspected offending agent (ceftriaxone)
  • If antibiotics are still needed, switch to a different class
  • Supportive care; antipyretics are not typically necessary
  • Monitor for resolution of fever
  • Drug fever is a diagnosis of exclusion; ensure no other source
  1. Resolution timeline:
  • Fever typically resolves within 48-72 hours of discontinuing the offending drug
  • May take longer (up to 5-7 days) for drugs with long half-lives
  • Rapid resolution supports the diagnosis
  • Persistent fever beyond 72 hours should prompt evaluation for alternative causes

Learning Points

  1. Classic FUO requires temperature >38.3°C for >3 weeks without diagnosis after adequate workup; major categories include infectious, neoplastic, autoimmune, and miscellaneous causes.
  1. Neutropenic fever is a medical emergency requiring prompt empiric broad-spectrum antibiotics; anti-pseudomonal beta-lactam monotherapy is first-line.
  1. Drug fever should be suspected when fever develops 7-10 days after starting a new medication, especially with relative bradycardia, eosinophilia, and rash.
  1. Systematic approach to fever includes thorough history (travel, exposures, medications), physical examination, and targeted workup based on clinical suspicion.
  1. Specific fever patterns (e.g., Pel-Ebstein in Hodgkin lymphoma, tertian in malaria) may provide diagnostic clues but are rarely pathognomonic.

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