Ketamine is a rapid-acting, non-barbiturate, phencyclidine derivative dissociative anesthetic agent. It is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist. In the Indian context, it is a critical drug used primarily for induction and maintenance of anesthesia, procedural sedation, and analgesia, especially in resource-limited settings due to its favorable hemodynamic profile and minimal respiratory depression. The 50mg/ml concentration is a standard injectable formulation.
Adult: IV Induction: 1-2 mg/kg (0.5-1.5 mg/kg when combined with other agents). IV Maintenance: 0.5-1 mg/kg as needed. IM: 4-6 mg/kg for procedural sedation. Infusion for analgesia: 0.1-0.5 mg/kg/hr.
Note: For IV use: Administer as a slow IV injection over 60 seconds to minimize cardiovascular stimulation and emergence reactions. For IM use: Inject deeply into a large muscle mass. Must be administered by trained healthcare professionals in a setting equipped for airway management and resuscitation. Premedication with an anticholinergic (e.g., atropine/glycopyrrolate) reduces secretions. A benzodiazepine (e.g., midazolam) premedication reduces emergence reactions.
Ketamine produces a functional and electrophysiological dissociation between the thalamocortical and limbic systems, leading to a trance-like cataleptic state. The patient appears awake but is detached from the environment and unresponsive to painful stimuli.
Pregnancy: Category B (Animal studies show no risk, human studies inadequate). Use only if clearly needed, especially in the 3rd trimester, as it may cause fetal depression. Can be used for cesarean section; rapidly crosses placenta.
Driving: Patients must NOT drive, operate machinery, or make important decisions for at least 24 hours after administration due to residual sedation, dizziness, and possible perceptual disturbances.
| Theophylline, Aminophylline | Increased risk of seizures | Major |
| Halothane | Potentiates halothane's cardiac depressant effects and may increase risk of arrhythmias | Major |
| Benzodiazepines (e.g., Midazolam, Diazepam) | Reduces emergence reactions and prolongs sedation. Pharmacodynamic synergy. | Moderate |
| Opioids (e.g., Fentanyl, Morphine) | Enhanced respiratory and CNS depression. Synergistic analgesia. | Major |
| Sympathomimetics (e.g., Epinephrine) | Additive hypertensive and tachycardic effects | Major |
| Thyroid hormones | Potentiates hypertensive and tachycardic effects | Moderate |
| CNS Depressants (Alcohol, Barbiturates) | Additive CNS and respiratory depression | Major |
| CYP3A4 Inhibitors (e.g., Clarithromycin, Ketoconazole, Ritonavir) | Increased ketamine plasma levels, prolonged effect | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | Decreased ketamine plasma levels, reduced effect | Moderate |
Same composition (Ketamine (50mg/ml)), different brands: