Ketamine for chronic pain: risks and benefits

Area of Science:

• Anesthesiology
• Pain Management
• Pharmacology

Background:

• Ketamine is an anesthetic used for chronic pain, particularly neuropathic pain.
• Its analgesic effects are primarily attributed to N-methyl-D-aspartate receptor inhibition, with possible contributions from descending inhibition and anti-inflammatory actions.
• While short-term ketamine infusions provide analgesia during administration, prolonged infusions (4-14 days) suggest sustained pain relief for up to 3 months.

Purpose of the Study:

• To review the efficacy and safety of ketamine for chronic neuropathic pain.
• To evaluate the duration of analgesic effects from prolonged ketamine infusions.
• To discuss the risks and benefits of ketamine use in clinical settings versus recreational abuse.

Main Methods:

• Review of current clinical data on ketamine infusions for chronic pain syndromes.
• Analysis of studies investigating short-term and prolonged ketamine administration.
• Comparison of side effect profiles in clinical use versus recreational ketamine abuse.

Main Results:

• Low-dose ketamine demonstrates potent analgesia in neuropathic pain states.
• Prolonged ketamine infusions show potential for long-term pain relief extending beyond the infusion period.
• Clinical ketamine use is associated with side effects including psychedelic symptoms, nausea, somnolence, and cardiovascular stimulation; hepatotoxicity is noted in a minority of patients.
• Recreational ketamine abuse carries significant risks, including bladder/renal complications and persistent psychiatric issues, but direct extrapolation to clinical settings is challenging.

Conclusions:

• Ketamine is effective for therapy-resistant severe neuropathic pain, with prolonged infusions offering extended benefits.
• While generally well-tolerated in clinical settings with appropriate monitoring and management of side effects (e.g., using benzodiazepines), careful patient observation for CNS, hemodynamic, renal, hepatic, and abuse-related symptoms is mandatory.
• Further research is needed to definitively establish the risk-benefit ratio, and ketamine use should be reserved for severe, refractory neuropathic pain until conclusive evidence is available.