What is the half-life of kratom?

Half-Life of Kratom

The terminal half-life of mitragynine, the primary active alkaloid in kratom, is approximately 23.24±16.07 hours (about 1 day) in humans. 1

Pharmacokinetic Profile of Kratom

Kratom (Mitragyna speciosa) contains multiple alkaloids with varying pharmacokinetic properties. The most recent and comprehensive human pharmacokinetic studies reveal important characteristics:

Primary Alkaloids and Their Properties

• Mitragynine (3S configuration):

  • Terminal half-life: 23.24±16.07 hours 1
  • Time to maximum concentration: 1-2 hours 2
  • Volume of distribution: 38.04±24.32 L/kg 1
  • Follows a two-compartment oral model 1

• Other 3S Configuration Alkaloids (speciogynine, paynantheine):

  • Terminal half-life: 24-45 hours 2
  • Higher volume of distribution (960-12,700 L) 2
  • Shorter time to maximum concentration (1-2 hours) 2

• 3R Configuration Alkaloids (mitraciliatine, speciociliatine, isopaynantheine):

  • Shorter terminal half-life: 12-18 hours 2
  • Lower volume of distribution (46-130 L) 2
  • Longer time to maximum concentration (2.5-4.5 hours) 2

Clinical Implications of Kratom's Half-Life

Metabolism and Elimination

• Only 0.14% of mitragynine is excreted unchanged in urine 1
• The FDA has warned against kratom use due to its potential for serious adverse effects 3

Drug Interactions

• Kratom alkaloids can inhibit CYP2D6 and CYP3A enzymes, potentially leading to dangerous drug interactions 4
• These interactions may contribute to polyintoxications when kratom is combined with other substances 4

Withdrawal Considerations

• The relatively long half-life of mitragynine (approximately 1 day) means withdrawal symptoms may be delayed
• For patients with kratom use disorder, buprenorphine has been used successfully as a treatment option 5

Comparison to Other Substances

For context, kratom's half-life can be compared to other substances:

• Methadone: 8 to >120 hours 3
• Fentanyl: 30-60 minutes 3
• Midazolam: 15-80 minutes 3
• Flumazenil: 0.7-1.3 hours 3

Safety Concerns

The Society for Perioperative Assessment and Quality Improvement (SPAQI) recommends against the use of kratom due to its potential for serious adverse effects 3. If a patient is using kratom, it should ideally be discontinued before elective procedures.

The pharmacokinetic linearity and long half-life of kratom's primary alkaloids contribute to both its therapeutic potential and its risk profile, requiring careful consideration in clinical settings.