Usage
- Ketamine is prescribed for the induction and maintenance of general anesthesia, procedural sedation (e.g., for painful procedures like wound debridement, fracture reduction), and increasingly for treatment-resistant depression and other mental health conditions like anxiety and PTSD. It also finds use as an analgesic for acute pain management, particularly in prehospital and emergency settings.
- Pharmacological classification: Dissociative anesthetic, analgesic, antidepressant.
- Mechanism of Action (brief): Ketamine primarily acts as an NMDA receptor antagonist, blocking the action of the excitatory neurotransmitter glutamate. It also interacts with other receptors, including opioid, monoaminergic, and muscarinic receptors, contributing to its complex effects.
Alternate Names
- Ketalar, Ketaject
- Brand names: Ketalar, Ketaset
How It Works
- Pharmacodynamics: Ketamine produces a dissociative state characterized by analgesia, amnesia, and altered perception of reality. It also exhibits bronchodilatory and sympathomimetic effects.
- Pharmacokinetics:
- Absorption: Rapid absorption following IV, IM, or intranasal administration. Oral absorption is slower and subject to first-pass metabolism.
- Metabolism: Primarily hepatic, via N-demethylation to norketamine (also active, but less potent). CYP3A4 is the primary enzyme involved.
- Elimination: Renal excretion of metabolites.
- Mode of Action: Ketamine’s primary mechanism involves non-competitive antagonism of the NMDA receptor, a subtype of glutamate receptor. This blockade of excitatory neurotransmission is thought to underlie its anesthetic and analgesic effects. It also modulates other receptors, including opioid, monoaminergic (serotonin, dopamine), and muscarinic cholinergic receptors.
- Receptor Binding/Enzyme Inhibition: NMDA receptor antagonist, also interacts with opioid, monoaminergic, and muscarinic receptors.
- Elimination Pathways: Primarily hepatic metabolism followed by renal excretion.
Dosage
Standard Dosage
Adults:
- Anesthesia (IV): Induction: 1-4.5 mg/kg over 60 seconds; Maintenance: 0.1-0.5 mg/min infusion or intermittent boluses.
- Anesthesia (IM): 6.5-13 mg/kg.
- Procedural Sedation (IV): 0.5-2 mg/kg, with or without adjunctive agents.
- Treatment-Resistant Depression (IV): 0.5 mg/kg over 40 minutes, typically twice weekly.
Children:
- Anesthesia (IV): Similar to adults, but doses may be adjusted based on age and weight.
- Procedural Sedation: 1.5-2 mg/kg IV over 30-60 seconds, with incremental doses as needed.
Special Cases:
- Elderly Patients: Start with lower doses and titrate cautiously.
- Patients with Renal Impairment: No specific FDA recommendations, but caution is advised. Consider dose reduction.
- Patients with Hepatic Dysfunction: No specific FDA recommendations, but caution is advised.
- Patients with Comorbid Conditions: Careful consideration is required for patients with cardiovascular, respiratory, or psychiatric conditions.
Clinical Use Cases
- Intubation: 1-2 mg/kg IV.
- Surgical Procedures: Dose depends on the procedure and desired level of anesthesia. See adult and pediatric dosing above.
- Mechanical Ventilation: Continuous infusion titrated to effect.
- Intensive Care Unit (ICU) Use: Analgesia and sedation: titrated to effect.
- Emergency Situations: Variable, depending on the specific situation.
Dosage Adjustments
- Dose adjustments may be needed based on patient response, renal/hepatic function, and concomitant medications.
Side Effects
Common Side Effects
- Nausea, vomiting, dizziness, hallucinations, confusion, increased blood pressure, increased heart rate.
Rare but Serious Side Effects
- Laryngospasm, respiratory depression, anaphylaxis, emergence delirium.
Long-Term Effects
- Cognitive impairment, bladder toxicity (with chronic use).
Adverse Drug Reactions (ADR)
- Severe emergence reactions, hypersensitivity reactions.
Contraindications
- Hypersensitivity to ketamine, severe cardiovascular disease (e.g., unstable angina, uncontrolled hypertension), increased intracranial pressure.
Drug Interactions
- Alcohol, benzodiazepines, other CNS depressants, halothane, thyroid hormone.
Pregnancy and Breastfeeding
- FDA Category C. Use with caution during pregnancy only if the benefits outweigh the risks.
- Limited data available on breastfeeding. Exercise caution.
Drug Profile Summary
- Mechanism of Action: NMDA receptor antagonist.
- Side Effects: Nausea, vomiting, dizziness, hallucinations, emergence delirium.
- Contraindications: Hypersensitivity, severe cardiovascular disease, increased intracranial pressure.
- Drug Interactions: Alcohol, benzodiazepines, halothane.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: See detailed dosing section above.
- Monitoring Parameters: Heart rate, blood pressure, respiratory rate, oxygen saturation.
Popular Combinations
- Midazolam (to reduce emergence reactions).
- Opioids (for enhanced analgesia).
Precautions
- General Precautions: Monitor vital signs, airway, and oxygenation.
- Specific Populations: See special cases under dosage.
- Lifestyle Considerations: Avoid alcohol and operating machinery after receiving ketamine.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Ketamine?
A: Dosage varies depending on the indication and route of administration. Refer to the detailed dosage section above.
Q2: How is Ketamine administered?
A: Ketamine can be administered intravenously (IV), intramuscularly (IM), intranasally (IN), orally (PO), and subcutaneously (SC).
Q3: What are the common side effects of Ketamine?
A: Common side effects include nausea, vomiting, dizziness, hallucinations, confusion, increased blood pressure, and increased heart rate.
Q4: What are the contraindications for Ketamine use?
A: Contraindications include hypersensitivity to ketamine, severe cardiovascular disease, increased intracranial pressure, and active psychosis.
Q5: How does Ketamine work in treatment-resistant depression?
A: Ketamine’s antidepressant effects are thought to be related to its ability to rapidly increase synaptic plasticity and modulate glutamate neurotransmission.
Q6: Does Ketamine interact with other medications?
A: Yes, ketamine can interact with other medications, including CNS depressants, halothane, and thyroid hormone.
Q7: Is Ketamine safe to use during pregnancy?
A: Ketamine is FDA Pregnancy Category C. Use with caution during pregnancy only if the benefits outweigh the risks.
Q8: What are the monitoring parameters for patients receiving Ketamine?
A: Monitor heart rate, blood pressure, respiratory rate, oxygen saturation, and level of consciousness.
Q9: How long do the effects of Ketamine last?
A: The duration of ketamine’s effects depends on the dose and route of administration. Generally, the effects of a single dose last for 30-60 minutes, but the antidepressant effects can persist for days or weeks.
This information is current as of February 16, 2025, and is intended for use by qualified medical professionals in India. Medical practices and guidelines are subject to change, so it is essential to consult the latest available resources and individualize treatment decisions based on patient needs.
