Ketamine

1. Introduction

Ketamine is a dissociative anaesthetic with sedative, analgesic, and amnestic properties. It acts primarily as an NMDA receptor antagonist, altering perception, pain, and consciousness. Ketamine is used in various medical fields, including anaesthesia, pain management, and mental health treatments.

2. Indications

  • Approved Indications:
    • Induction and maintenance of general anaesthesia.
    • Procedural sedation (short diagnostic or surgical procedures).
    • Severe acute pain (e.g., trauma, burns).
  • Off-Label Uses:
    • Treatment-resistant depression (TRD).
    • Suicidal ideation (rapid-acting intervention).
    • Chronic pain syndromes (e.g., complex regional pain syndrome, neuropathic pain).
    • Palliative care (analgesia and sedation).

3. Dosage

  • Anaesthesia (IV/IM):
    • Induction:
      • IV: 1–4.5 mg/kg (typical dose: 2 mg/kg).
      • IM: 6–13 mg/kg.
    • Maintenance:
      • IV infusion: 10–45 mcg/kg/min.
      • Intermittent IV boluses: 0.5–2 mg/kg as needed.
  • Procedural Sedation (IV/IM):
    • IV: 1–2 mg/kg over 1 minute.
    • IM: 4–5 mg/kg.
  • Treatment-Resistant Depression (Intranasal or IV):
    • Intranasal (Esketamine): 56–84 mg twice weekly.
    • IV: 0.5 mg/kg over 40 minutes, repeated weekly or biweekly.
  • Pain Management (Sub-anaesthetic Doses):
    • IV infusion: 0.1–0.5 mg/kg/hour.

4. Administration

  • Administer under medical supervision in a controlled setting.
  • IV Use: Administer slowly to avoid respiratory depression.
  • IM Use: For rapid onset, administer into a large muscle.
  • Intranasal Use: Administer as per the manufacturer’s instructions (Esketamine).

5. Forms Available

  • Injectable solution: 10 mg/mL, 50 mg/mL, 100 mg/mL.
  • Intranasal spray: 28 mg per spray (Esketamine).

6. Side Effects

6.1. Common Side Effects

  • Dissociation (altered sense of time, space, or reality).
  • Drowsiness or dizziness.
  • Nausea and vomiting.
  • Increased blood pressure and heart rate.

6.2. Less Common Side Effects

  • Hallucinations or vivid dreams.
  • Blurred vision.
  • Anxiety or restlessness.

6.3. Rare but Serious Side Effects

  • Respiratory depression (high doses or rapid IV administration).
  • Increased intracranial pressure.
  • Emergence reactions (confusion, agitation on waking).
  • Bladder dysfunction (with chronic use).

7. Warnings

  • Emergence Phenomenon: Patients may experience vivid dreams, hallucinations, or confusion as they awaken. Pre-medication with a benzodiazepine can reduce this risk.
  • Hypertension: Use cautiously in patients with poorly controlled high blood pressure.
  • Substance Misuse: Ketamine has the potential for abuse and dependence due to its dissociative and euphoric effects.

8. Precautions

  • Use cautiously in patients with:
    • Cardiovascular disease (risk of increased heart rate and blood pressure).
    • Psychiatric disorders (risk of worsening psychosis).
    • Increased intracranial pressure or head injury.
  • Avoid abrupt discontinuation in long-term use for depression or chronic pain.

9. Interactions

  • Drug-Drug Interactions:
    • Benzodiazepines: May reduce the psychotomimetic effects of ketamine.
    • CNS depressants (e.g., opioids, alcohol): Increased risk of respiratory depression.
    • Antihypertensives: Enhanced blood pressure-lowering effects.
  • Drug-Food Interactions:
    • Avoid food 6–8 hours before anaesthesia to reduce the risk of aspiration.

10. Monitoring Parameters

  • Blood pressure and heart rate during administration.
  • Respiratory rate and oxygen saturation.
  • Mental status during recovery (to monitor for emergence reactions).

11. Use in Children

  • Safe and commonly used for sedation and anaesthesia in paediatrics. Doses should be carefully adjusted by weight.

12. Use in Pregnancy

  • Category C: Use only if the potential benefits outweigh risks. May cause neonatal depression if used during labour or near delivery.

13. Use in Elderly

  • Safe for use but start with lower doses due to increased sensitivity and comorbid conditions.

14. Use in Kidney Disease

  • No significant dose adjustments required, as ketamine is primarily metabolised in the liver.

15. Use in Liver Disease

  • Use cautiously in patients with severe liver impairment, as ketamine metabolism may be affected.

16. Patient Counselling Points

  • Explain the potential for dissociation or vivid dreams during or after treatment.
  • Avoid operating machinery or driving for 24 hours after administration.
  • For depression treatment: Attend all scheduled follow-ups and report any worsening symptoms.
  • Avoid alcohol or recreational drugs while undergoing ketamine therapy.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
Ketalar (injection)Pfizer$50–100 (10 mL, 50 mg/mL)
Spravato (Esketamine nasal spray)Janssen Pharmaceuticals$590–885 per dose
Generic KetamineVarious manufacturers$20–50 (10 mL, 50 mg/mL)

18. FAQs (15 Questions)

  1. What is ketamine used for?
    It is used for anaesthesia, pain management, and treatment-resistant depression.
  2. How does ketamine work?
    It blocks NMDA receptors in the brain, altering pain perception, consciousness, and mood regulation.
  3. How is ketamine administered?
    It can be administered via IV, IM, or intranasal routes under medical supervision.
  4. What are common side effects of ketamine?
    Dissociation, nausea, increased blood pressure, and vivid dreams are common.
  5. Can ketamine cause hallucinations?
    Yes, hallucinations or vivid dreams can occur, especially at higher doses.
  6. Is ketamine addictive?
    Yes, ketamine has potential for abuse and dependence if misused.
  7. How long does ketamine take to work for depression?
    Effects on mood may begin within hours, with peak benefits within 24–48 hours.
  8. Can ketamine cause respiratory depression?
    Yes, but this is rare at therapeutic doses and usually occurs with rapid or high-dose IV administration.
  9. Is ketamine safe for children?
    Yes, it is widely used for paediatric anaesthesia and sedation.
  10. Can I drive after receiving ketamine?
    No, avoid driving or operating heavy machinery for at least 24 hours after administration.
  11. Does ketamine cause high blood pressure?
    Yes, it can increase blood pressure and heart rate temporarily.
  12. Is ketamine safe during pregnancy?
    Use cautiously, as it may affect the foetus. Consult your doctor before use.
  13. What is esketamine, and how is it different from ketamine?
    Esketamine is a nasal spray form of ketamine, approved specifically for depression. It has a slightly different chemical structure.
  14. Can ketamine treat chronic pain?
    Yes, it can be used in low doses to manage chronic pain, such as in complex regional pain syndrome.
  15. How should ketamine be stored?
    Store at room temperature, away from light and moisture.