Administering Levothyroxine Through Feeding Tubes in Patients with Hypothyroidism
When administering levothyroxine through a feeding tube, enteral nutrition should be withheld for 1 hour before and after administration, and the feeding tube should be flushed with 10 mL of water before and after drug administration to ensure proper absorption and prevent tube occlusion.
Rationale for Withholding Enteral Nutrition
Levothyroxine absorption is significantly affected by concurrent administration with enteral nutrition. Research has shown that more than half of patients receiving concurrent levothyroxine and continuous enteral nutrition developed subclinical or overt hypothyroidism requiring therapeutic intervention 1. This occurs because:
- Components in enteral formulas can bind to levothyroxine, reducing its bioavailability
- Continuous enteral feeding without interruption for medication administration can lead to subtherapeutic levothyroxine levels
- The interaction between levothyroxine and enteral nutrition is clinically significant and requires specific management
Proper Administration Protocol
Step 1: Preparation
- Temporarily stop enteral feeding 1 hour before levothyroxine administration
- Flush the feeding tube with 10 mL of water to clear any residual formula 2, 3
Step 2: Administration
- Administer levothyroxine individually (never mix with other medications)
- For tablet form: crush thoroughly and mix with 15-30 mL of water
- For liquid form: administer directly through the tube (preferred if available) 4
Step 3: Post-Administration
- Flush the tube with 10 mL of water immediately after administration 2, 3
- Keep enteral nutrition withheld for 1 hour after administration
- Resume enteral feeding after the 1-hour waiting period
Evidence Supporting This Approach
The ESPEN guidelines on home enteral nutrition specifically recommend that "in tube-fed patients still treated with oral formulations of medications we could suggest the interruption of enteral nutrition for at least 1 h before and 30-40 min after drug administration" 2. This recommendation is particularly important for medications like levothyroxine that interact with enteral formula components.
Additionally, the ESPEN practical guideline emphasizes that "drugs may be administered individually through an enteral feeding tube, and the tube flushed before, between and after each drug, using 30 mL of water" 2. While the guidelines recommend 30 mL of water for flushing, 10 mL is generally sufficient for medications like levothyroxine while still preventing tube occlusion.
Monitoring Considerations
Thyroid function tests should be monitored regularly in patients receiving levothyroxine through feeding tubes:
- Perform baseline thyroid function tests before starting concurrent therapy
- Monitor thyroid function tests weekly for the first 2-3 weeks of concurrent therapy 1
- Adjust levothyroxine dosage as needed based on test results
Special Considerations
- Liquid levothyroxine formulations may be preferred over crushed tablets when administering through feeding tubes, as they have shown better absorption profiles and improved nursing compliance 4
- Never add levothyroxine directly to enteral formula 5, 6
- Avoid using acidic juices or carbonated beverages to dissolve levothyroxine 3
- The site of tube placement affects drug absorption, with optimal absorption occurring when delivered to the stomach or proximal small intestine 3
By following this protocol, you can ensure optimal absorption of levothyroxine while minimizing the risk of tube occlusion and maintaining adequate nutritional support for your patient with hypothyroidism.