Can diphenhydramine and diazepam be given to a patient with nothing by mouth (NPO) status before a coronary angiogram?

Administration of Diphenhydramine and Diazepam in NPO Patients Before Coronary Angiography

Both diphenhydramine and diazepam can be safely administered to patients with NPO status before coronary angiography, as these medications do not increase procedural risks and may help manage anxiety and allergic reactions.

Medication Administration During NPO Status

General Considerations

• NPO (nothing by mouth) status is typically required before coronary angiography to reduce aspiration risk
• However, certain medications may still be given depending on their importance and risk profile
• Small sips of water with essential medications are generally permitted even during NPO status

Specific Recommendations for Pre-Angiography Medications

Diphenhydramine (Benadryl)

• Can be safely administered before coronary angiography for:

  • Prophylaxis in patients with prior anaphylactoid reactions to contrast media
  • Management of anxiety or mild sedation

• Administration guidelines:

  • Typically given as part of a premedication regimen (50 mg orally 1 hour before procedure) 1
  • For patients with strict NPO status, parenteral (IV/IM) administration is preferred

Diazepam (Valium)

• Can be safely administered before coronary angiography for:

  • Anxiolysis and conscious sedation
  • Management of agitation

• Administration guidelines:

  • Oral administration (typically 5-10 mg) if NPO restrictions allow small sips of water
  • IV administration (2-5 mg) is preferred for strict NPO patients

Evidence-Based Rationale

Safety Considerations

• Neither medication increases risk of procedural complications during coronary angiography
• The 2011 ACCF/AHA guidelines for PCI specifically mention that patients with prior anaphylactoid reactions to contrast media should receive appropriate steroid and antihistamine prophylaxis before contrast administration 1
• The combination of diazepam and diphenhydramine has been shown to be effective for sedation 2

Timing Considerations

• If oral administration is permitted with small sips of water:

  • Diphenhydramine should be given 1 hour before the procedure
  • Diazepam should be given 30-60 minutes before the procedure

• For strict NPO patients:

  • IV administration is preferred for both medications
  • Diphenhydramine 25-50 mg IV
  • Diazepam 2-5 mg IV (slow administration)

Special Situations

Contrast Reaction Prophylaxis

• For patients with history of contrast reactions, a regimen including diphenhydramine is recommended:
  • 50 mg of diphenhydramine 1 hour before procedure
  • 50 mg of prednisone administered 13 hours, 7 hours, and 1 hour before procedure 1
  • In practice, 60 mg of prednisone the night before and morning of procedure plus 50 mg of diphenhydramine 1 hour before is often used 1

Common Pitfalls to Avoid

1. Oversedation: Excessive sedation may compromise patient cooperation and respiratory status
2. Delayed administration: Ensure medications are given with sufficient time to take effect
3. Withholding necessary medications: Do not withhold these medications when indicated simply due to NPO status
4. Ignoring alternative routes: Use IV/IM routes when oral administration is not possible

Recent Evidence on Fasting Requirements

Recent research (CORO-NF study) suggests that shorter fasting periods before coronary angiography (as little as 2 hours) may be safe and associated with higher patient satisfaction without increased complications 3. This suggests that oral medications may be safely administered closer to procedure time than previously thought.

In conclusion, both diphenhydramine and diazepam can be safely administered to patients with NPO status before coronary angiography when clinically indicated, with preference for parenteral routes in strict NPO situations.