What alternatives are available if oral medications are not tolerated?

Alternative Routes of Medication Administration When Oral Medications Are Not Tolerated

When oral medications cannot be tolerated, parenteral routes (intravenous, subcutaneous, transdermal, or rectal) should be used as alternatives to ensure medication delivery and maintain therapeutic efficacy. 1

Common Reasons for Oral Medication Intolerance

• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Dysphagia or swallowing difficulties
• Bowel obstruction
• Severe mucositis
• Unconscious or sedated patients
• Severe oral pain or inflammation

Alternative Administration Routes

Intravenous (IV) Administration

• First-line alternative for most medications requiring rapid onset or when other routes aren't feasible
• Particularly important in:
  • Small bowel obstruction 1
  • Severe vomiting
  • Critical illness requiring precise dosing
• Examples of commonly used IV medications:
  • Antibiotics (e.g., ceftriaxone 2, vancomycin 3)
  • Pain medications (morphine, hydromorphone)
  • Antiemetics

Subcutaneous Administration

• Useful for:
  • Opioid pain management in palliative care 4
  • When IV access is difficult
  • Long-term medication delivery
• Common medications administered subcutaneously:
  • Morphine, hydromorphone
  • Metoclopramide for nausea 4
  • Octreotide for diarrhea control 4

Transdermal Administration

• Provides sustained drug delivery through skin
• Particularly useful for:
  • Pain management (fentanyl, buprenorphine) 4
  • Patients with stable medication requirements
• Benefits:
  • Avoids first-pass metabolism
  • Provides steady drug levels
  • Reduces pill burden

Rectal Administration

• Alternative when oral and IV routes unavailable
• Useful for:
  • Antiemetics
  • Antipyretics
  • Some pain medications
  • Laxatives

Special Considerations by Clinical Scenario

Palliative Care Setting

• For patients unable to take oral medications, transdermal fentanyl or buprenorphine are preferred for stable pain 4
• For breakthrough pain, subcutaneous morphine or hydromorphone should be used 4
• For nausea/vomiting, consider rectal antiemetics or subcutaneous metoclopramide 4

Small Bowel Obstruction

• All oral medications should be discontinued 1
• IV route is preferred for all necessary medications
• Avoid antimotility agents as they may worsen obstruction 1

Severe Infection Requiring Antibiotics

• IV antibiotics are the standard of care when oral route is compromised 4
• For intra-abdominal infections with oral intolerance, IV options include:
  • Meropenem 1g q6h by extended infusion
  • Imipenem/cilastatin 500mg q6h
  • For beta-lactam allergy: eravacycline 1mg/kg q12h 4

Medication-Specific Considerations

Pain Management

• For moderate to severe pain when oral medications aren't tolerated:
  • Transdermal fentanyl or buprenorphine for stable pain
  • IV or subcutaneous morphine for acute pain or titration 4
  • The average relative potency ratio of oral to IV morphine is between 1:2 and 1:3 4

Antiemetics

• For persistent nausea/vomiting:
  • IV or subcutaneous metoclopramide
  • IV ondansetron
  • Rectal prochlorperazine suppositories

Antibiotics

• Most antibiotics have IV formulations
• Some antibiotics have incompatibilities with other IV medications:
  • Vancomycin is incompatible with ceftriaxone in admixtures 2
  • Administer sequentially with thorough flushing between medications

Common Pitfalls and Caveats

1. Medication compatibility issues: Always check compatibility when administering multiple IV medications 2

2. Conversion errors: Use appropriate conversion ratios when switching from oral to parenteral routes (e.g., oral to IV morphine ratio is 1:2 to 1:3) 4

3. Inappropriate route selection: Not all medications have equivalent bioavailability across different routes

4. Administering oral medications through NG tubes in bowel obstruction: This can worsen patient outcomes and should be avoided 1

5. Overlooking drug-specific considerations: Some medications require special handling when changing routes (e.g., extended-release formulations cannot be crushed for NG administration) 1

By selecting appropriate alternative routes when oral medications cannot be tolerated, clinicians can ensure continued effective treatment while minimizing patient discomfort and potential complications.