From the Guidelines
The half-life of morphine is approximately 2-4 hours, as indicated by the most recent and highest quality study available 1. This means that after this time period, half of the drug has been eliminated from the body. The elimination half-life of morphine is an important consideration in clinical practice, as it affects the dosing frequency and the risk of accumulation or withdrawal. Some key points to consider when using morphine include:
- The plasma elimination half-life of morphine is 2–4 hours, with steady state achieved within 4–5 half-lives (24 hours) 1
- The duration of pain relief from a single dose is shorter, usually 3-4 hours for immediate-release formulations 1
- Morphine is metabolized primarily in the liver and excreted through the kidneys, so patients with liver or kidney impairment may experience prolonged half-lives and drug effects
- Age can also affect morphine's half-life, with elderly patients and neonates typically experiencing longer half-lives due to reduced clearance 1 The relatively short half-life of morphine explains why it is often dosed multiple times per day when treating acute pain, and why extended-release formulations were developed for chronic pain management. In clinical practice, the half-life of morphine should be taken into account when determining the dosing schedule and monitoring for potential side effects or interactions. For example, patients with renal impairment may require more frequent monitoring and dose adjustments to avoid accumulation of the drug 1. Overall, understanding the half-life of morphine is crucial for safe and effective use of this medication in clinical practice.
From the FDA Drug Label
The effective terminal half-life of morphine sulfate after IV administration is reported to be approximately 2 hours.
- The half-life of morphine is approximately 2 hours after IV administration, as stated in the drug label 2.
- Note that the half-life may vary depending on the specific population or administration method.
From the Research
Morphine Half-Life
- The half-life of morphine is reported to be around 2 to 3 hours 3
- Another study found the elimination half-life of morphine to be 4.4 hours 4
- A study on morphine pharmacokinetics and metabolism in humans found the half-life of morphine to be 15.1 +/- 6.5 hours 5
- The half-life of morphine can vary depending on the individual and the method of administration
Factors Affecting Morphine Half-Life
- Age does not appear to influence morphine half-life 3
- Surgical anesthesia may not markedly influence morphine half-life and disposition 3
- The metabolism of morphine to its metabolites, such as morphine-3-glucuronide and morphine-6-glucuronide, can affect its half-life 4, 5
- Enterohepatic cycling of morphine and its metabolites can also affect its half-life 5
Comparison with Other Studies
- A study on the relationship of pharmacokinetics to pharmacological activity found similar half-lives for morphine in normal volunteers and anesthetized patients 3
- Another study found that the half-life of morphine was not significantly affected by the administration of gabapentin 6
- A pilot study on the metabolism of codeine to morphine found that the half-life of codeine was affected by the administration of diazepam 7