How to dilute injectable morphine from 15 mg/mL?

Dilution of Injectable Morphine 15 mg/mL

For injectable morphine 15 mg/mL, dilute with sterile normal saline (0.9% sodium chloride) or sterile water for injection without preservatives, using the specific dilution ratio determined by your target concentration and clinical indication.

General Dilution Principles

The dilution method depends entirely on your target concentration and route of administration. Here are the most common clinical scenarios:

For Intravenous Infusion (1:1000 dilution for continuous infusion)

• Add 1 mL of morphine 15 mg/mL to 250 mL of D5W to create a 60 mcg/mL (0.06 mg/mL) solution for continuous IV infusion 1
• This allows precise titration at 1-4 mcg/min initially, increasing to maximum 10 mcg/min 1
• Alternative: Add 1 mg (approximately 0.067 mL of your 15 mg/mL solution) to 100 mL saline for a 1:100,000 solution, administered at 30-100 mL/h 1

For Intrathecal Administration

• Target concentration: 0.5-1.0 mg/mL for single-step dilution 2
• From your 15 mg/mL solution: withdraw 0.1 mL and add 1.4 mL sterile preservative-free normal saline to achieve approximately 1 mg/mL 2
• Single-step dilution is significantly more accurate than double-dilution techniques (P = 0.047) 2
• Critical: Use only preservative-free diluents for intrathecal use 2, 3

For Fortified Ophthalmic Use (if applicable)

While not standard for morphine, the dilution technique mirrors other ophthalmic preparations: calculate total volume needed based on desired final concentration, then add appropriate volume of sterile diluent 1

Diluent Selection

Preferred diluents in order of priority:

• 0.9% sodium chloride for injection USP (preservative-free) - most stable and compatible 1, 3
• Sterile water for injection (preservative-free) - acceptable alternative 3, 4
• D5W - acceptable for IV infusions only 1

Avoid: Lactated Ringer's solution (may contribute to metabolic acidosis) 1

Stability Considerations

• pH adjustment: Solutions should be adjusted to pH 3.2 for optimal stability during storage 5
• Oxygen exposure: Eliminate oxygen by flushing vials with nitrogen before sealing if storing diluted solutions 6, 5
• Temperature: Store at room temperature (20-25°C); avoid refrigeration (risk of precipitation) and heat (risk of water evaporation in polymer containers) 6
• Light protection: Store in light-protected containers 6, 4
• Expiration: Properly prepared preservative-free solutions stable for 6 months when compounded under sterile conditions 3
• Diluted solutions retain >95% potency for up to 3 months under ambient conditions when oxygen is excluded 6

Critical Safety Points

For intrathecal use:

• Dilution errors range from 25 mcg to 289 mcg when targeting 100 mcg doses 2
• Use prediluted solutions whenever possible to minimize dosing variability 2
• Never use preserved solutions intrathecally 2, 3

For IV bolus administration:

• Morphine can be given undiluted for IV bolus in emergency situations 1
• Starting dose for opioid-naïve adults: 2 mg IV bolus, repeated every 15 minutes as needed 1
• If already on morphine infusion and symptomatic: give bolus equal to 2× the hourly infusion rate 1

Sterile technique:

• All dilutions must be performed using aseptic technique 1, 3
• Filter through 0.22-micrometer filters if compounding batches 3

Practical Calculation Method

1. Determine target dose in mg
2. Determine target volume in mL
3. Calculate target concentration = dose (mg) ÷ volume (mL)
4. Calculate volume of 15 mg/mL stock needed = target dose (mg) ÷ 15 mg/mL
5. Calculate diluent volume = target volume - stock volume
6. Mix stock with calculated diluent volume