How is intravenous (IV) morphine injection prepared and administered?

Preparation and Administration of Intravenous Morphine

Intravenous morphine should be prepared from single-dose vials (typically 4 mg/mL concentration), inspected for discoloration or precipitate, and administered as a slow IV bolus over several minutes to avoid chest wall rigidity and respiratory depression. 1

Preparation

• Use single-dose vials containing morphine sulfate 4 mg/mL for intravenous administration 1
• Inspect the solution visually before administration for particulate matter and discoloration—do not use if the color is darker than pale yellow, discolored in any other way, or contains precipitate 1
• Store at room temperature (20°C to 25°C or 68°F to 77°F) and protect from light 1
• Do not freeze or heat-sterilize the solution 1
• Discard any unused portion as the vials contain no preservative or antioxidant 1
• Avoid dosing errors by clearly communicating both the total dose in mg AND the total volume when prescribing 1

Administration Technique

• Administer slowly via direct IV injection to prevent chest wall rigidity, which can occur with rapid administration 1
• Have naloxone and resuscitative equipment immediately available whenever initiating morphine therapy 1
• Limit administration to personnel familiar with managing respiratory depression, as this is the primary risk 1

Dosing Guidelines

Standard Adult Dosing

• Initial dose: 0.1 to 0.2 mg/kg every 4 hours as needed for pain management 1
• The FDA label specifies this as the usual starting dose in adults 1

Rapid Titration for Severe Pain

• For severe cancer pain emergencies: 2 mg boluses every 2 minutes until significant analgesia is achieved or adverse effects occur 2
• Alternative protocol: 1.5 mg boluses every 10 minutes until pain relief is total or drowsiness develops 3
• For acute severe pain: 0.1 mg/kg initial dose, then 0.05 mg/kg every 5 minutes provides faster relief than lower-dose protocols 4

Breakthrough Pain in Opioid-Tolerant Patients

• Use one-fifth (20%) of the total daily oral morphine dose, converted to IV using a 1:3 ratio (IV:oral) 5
• This provides pain relief within approximately 15-20 minutes 5
• Rescue doses can be given every 15-30 minutes during titration 6

Special Population Considerations

Renal or Hepatic Impairment

• Start with lower doses and titrate slowly while carefully monitoring for side effects 1
• Consider fentanyl or buprenorphine as safer alternatives in chronic kidney disease stages 4-5 (eGFR <30 mL/min) due to reduced risk of metabolite accumulation 7

Elderly or Debilitated Patients

• Use reduced doses as these patients have increased risk of respiratory depression 1
• Elderly patients may require lower doses due to altered pharmacokinetics 8

Pharmacokinetic Profile

• Peak effects occur within 15-30 minutes after IV administration 7, 6
• Duration of action is approximately 4 hours, which should guide dosing intervals 6, 8
• Elimination half-life is 1.5 to 2 hours in normal subjects 1

Critical Safety Warnings

• Respiratory depression is the primary risk, especially in patients with COPD, decreased respiratory reserve, or pre-existing respiratory depression 1
• High doses can cause CNS excitation and convulsions 1
• Rapid IV administration may result in chest wall rigidity, making ventilation difficult 1
• Monitor for cardiovascular instability with high doses, which can cause sympathetic hyperactivity 1
• Common adverse effects include nausea, vomiting, sedation, and constipation 6, 1

Conversion Ratios

• The oral to IV morphine ratio is 1:2 to 1:3 (meaning 20-30 mg oral morphine equals approximately 10 mg IV morphine) 7, 8
• When converting from oral to IV, divide the oral dose by 3 for roughly equianalgesic effect, then adjust as needed 7
• The IV to subcutaneous ratio is 1:1 (same potency by both parenteral routes) 7

Common Pitfalls to Avoid

• Do not confuse different morphine concentrations when prescribing or administering—this can result in accidental overdose and death 1
• Do not use buccal, sublingual, or nebulized routes as absorption is unpredictable with no clinical advantage 7, 6
• A single 0.1 mg/kg dose is insufficient for controlling severe acute pain in the majority of patients—67% will have less than 50% pain reduction 9
• Avoid using morphine in patients with renal failure without dose adjustment due to accumulation of active metabolites 7