Can heparin be formulated in normal saline?

Heparin Can Be Safely Formulated in Normal Saline

Yes, heparin can be safely formulated in normal saline (0.9% sodium chloride) and this is actually the preferred diluent for heparin solutions. 1, 2, 3

Evidence for Heparin in Normal Saline

Stability and Effectiveness

• Heparin maintains its stability and anticoagulant activity for at least 24 hours when diluted in normal saline and stored in plastic containers 2
• Studies have demonstrated that heparin activity remains stable in normal saline for up to 24 hours, whereas there can be a 40-55% inactivation when formulated in solutions containing dextrose or lactate 3

Clinical Applications

• Normal saline is routinely used as a diluent for heparin in various clinical settings:
  • For catheter flushing and locking solutions
  • For continuous intravenous infusions
  • For preparation of heparin-containing solutions

Guidelines for Heparin Use with Normal Saline

The ESPEN guidelines on parenteral nutrition provide clear recommendations:

1. For catheter maintenance:

   • Most central venous access devices can be safely flushed and locked with saline solution when not in use (Grade B) 1
   • When heparin is used for locking catheters, proper flushing with saline before heparinization is more important than the heparin concentration itself 1

2. For parenteral nutrition administration:

   • Since heparin may facilitate precipitation of lipids, saline flushing is mandatory during parenteral nutrition with lipids before any flushing with heparin (Grade B) 1
   • A saline flush should always be interposed between lipid-containing PN admixtures and heparin 1

Heparin Concentration Considerations

• For heparin-lock maintenance, a concentration as low as 10 USP units of sodium heparin per milliliter of normal saline solution is effective for maintaining patency without affecting clotting parameters 4
• For catheter locking, most authors suggest using a concentration between 50 and 500 units per mL (Grade C) 1
• When using heparin for continuous infusion, normal saline is the preferred diluent 2, 3

Important Precautions

1. Compatibility with other medications:

   • While heparin in normal saline is compatible with certain penicillins (benzylpenicillin, ampicillin, methicillin), it may not be compatible with all antibiotics 3
   • Vancomycin and gentamicin in heparin/saline solutions maintain stability for up to 4 weeks when refrigerated 5

2. Storage considerations:

   • Plastic containers are preferred over glass when storing heparin solutions for extended periods 2
   • pH changes (3.5-10.0) have minimal effect on heparin stability in solution 2

3. Potential adverse effects:

   • Be aware of potential complications of heparin use including bleeding, thrombocytopenia, allergic reactions, and osteoporosis 1
   • In premature newborns, there may be increased risk of intraventricular hemorrhage 1

Recent Trends in Practice

Recent guidelines suggest that normal saline alone (without heparin) may be sufficient for maintaining catheter patency:

• The 2023 ESPEN practical guideline for home parenteral nutrition recommends: "Sodium chloride 0.9% instead of heparin should be used to lock long-term CVAD" (Grade B) 1
• This recommendation is based on evidence that normal saline flushing is not inferior to heparin flushing regarding catheter occlusion, and has a lower risk of biofilm formation in the catheter lumen 1

In conclusion, heparin can be safely and effectively formulated in normal saline, and this combination is widely used in clinical practice. For many applications, normal saline alone may be sufficient and even preferable to heparin-containing solutions.