Is Benadryl (diphenhydramine) bad for pneumonia?

Diphenhydramine (Benadryl) in Pneumonia Management

Diphenhydramine (Benadryl) should generally be avoided in patients with pneumonia as it can worsen respiratory outcomes by thickening secretions and suppressing cough, which is an important protective mechanism for clearing the airways.

Mechanism and Concerns

Diphenhydramine affects pneumonia management in several problematic ways:

1. Suppression of protective cough reflex:

   • While diphenhydramine has been shown to inhibit cough reflex sensitivity in patients with acute viral respiratory infections 1, this effect is counterproductive in pneumonia.
   • Cough is a critical defense mechanism that helps clear secretions and pathogens from the lungs.

2. Anticholinergic effects:

   • First-generation antihistamines like diphenhydramine have strong anticholinergic properties that can thicken respiratory secretions.
   • This makes it more difficult for patients to clear infected mucus from their lungs.

3. Sedative effects:

   • The sedative properties of diphenhydramine may reduce respiratory drive and awareness.
   • This is particularly concerning in patients with respiratory compromise.

Evidence-Based Recommendations

Current pneumonia treatment guidelines do not recommend diphenhydramine as part of pneumonia management:

• The American Thoracic Society and Infectious Diseases Society of America guidelines focus on appropriate antimicrobial therapy with beta-lactams, macrolides, or fluoroquinolones depending on the clinical scenario 2.

• For respiratory secretion management in pneumonia, guidelines recommend:

  • Selective (M1, M3) receptor anticholinergic drugs to reduce secretions, relax airway smooth muscle, and improve pulmonary ventilation 3.
  • Not first-generation antihistamines like diphenhydramine.

Appropriate Pneumonia Management

Instead of diphenhydramine, pneumonia management should focus on:

1. Appropriate antimicrobial therapy:

   • For community-acquired pneumonia: beta-lactam plus macrolide or fluoroquinolone monotherapy 3, 2.
   • Treatment duration typically 5-7 days for uncomplicated cases, 10-14 days for more severe cases 3, 2.

2. Supportive care:

   • Oxygen therapy to maintain SaO2 >92% 2.
   • Adequate hydration and rest 2.
   • Analgesics for pleuritic pain if needed 3.

3. Secretion management:

   • Proper hydration to maintain thin secretions.
   • Selective anticholinergics when indicated 3.
   • Positioning and appropriate airway clearance techniques.

Special Considerations

Patients with neuromuscular disorders or other conditions affecting cough strength are at particularly high risk when given medications that suppress cough reflex:

• These patients already have ineffective cough and are predisposed to respiratory infections 4.
• Cough suppression with diphenhydramine could further compromise their ability to clear secretions.

Bottom Line

Diphenhydramine should be avoided in patients with pneumonia. While it may provide symptomatic relief for cough in simple upper respiratory infections, its anticholinergic and cough-suppressive properties can interfere with the body's natural defense mechanisms needed to recover from pneumonia, potentially leading to worsened outcomes, including respiratory failure.

If symptom management is needed for pneumonia patients, consult with a healthcare provider about safer alternatives that won't compromise respiratory function or recovery.