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 10mg oral formulation, it is primarily used as an adjunctive treatment for treatment-resistant depression (TRD) and chronic neuropathic pain, under strict medical supervision. It produces a trance-like state providing pain relief, sedation, and amnesia. Its unique mechanism provides rapid antidepressant effects, often within hours, unlike conventional antidepressants.
Adult: For Treatment-Resistant Depression (Oral/Sublingual, off-label): Typically 0.5 mg/kg to 1 mg/kg, administered 2-3 times per week initially. A 10mg dose is on the very low end and would be part of a titrated regimen, e.g., starting at 0.5 mg/kg (for a 70kg person = 35mg). Dosing is highly individualized. For Neuropathic Pain (Oral): 0.5 mg/kg to 1 mg/kg every 8-12 hours, titrated to effect. Maximum daily oral dose rarely exceeds 3 mg/kg/day.
Note: Oral 10mg tablets are typically used off-label. They may be administered sublingually (placed under the tongue to dissolve) to improve bioavailability and reduce first-pass metabolism. Patient should not eat or drink for 15 minutes before and after sublingual administration. Administration must occur in a clinical setting where vital signs (BP, HR, SpO2) and mental state can be monitored for at least 2 hours post-dose. Patient MUST NOT drive or operate machinery for 24 hours.
Ketamine's primary mechanism is the non-competitive antagonism of the N-methyl-D-aspartate (NMDA) receptor, an ionotropic glutamate receptor. This blockade, particularly in the thalamo-neocortical and limbic systems, leads to a functional dissociation between the thalamus and the limbic cortex, producing a 'dissociative anesthetic' state. Its rapid antidepressant effect is believed to involve a cascade: NMDA receptor blockade on GABAergic interneurons leads to disinhibition of glutamatergic neurons, resulting in a surge of glutamate. This activates AMPA receptors, triggering downstream pathways (BDNF release, mTOR activation) that promote synaptogenesis and reverse the synaptic deficits associated with depression.
Pregnancy: FDA Pregnancy Category: Not formally assigned, but often considered Category D (positive evidence of human fetal risk). Ketamine crosses the placenta. Use only if the potential benefit justifies the potential risk to the fetus, typically limited to essential surgical anesthesia. Not indicated for psychiatric use during pregnancy.
Driving: ABSOLUTELY CONTRAINDICATED for at least 24 hours after a dose. Ketamine impairs judgment, thinking, motor skills, and reaction time. Effects may be unpredictable and linger.
| Theophylline, Aminophylline | Increased risk of seizures when used concurrently with ketamine. | Major |
| CNS Depressants (e.g., Alcohol, Benzodiazepines, Opioids, Barbiturates) | Additive CNS and respiratory depression. However, benzodiazepines (e.g., midazolam) are often used prophylactically to reduce emergence reactions. | Major |
| Sympathomimetics (e.g., Epinephrine, Dopamine) | Additive hypertensive and tachycardic effects. | Major |
| Thyroid Hormones | Increased risk of hypertension and tachycardia. | Moderate |
| CYP3A4 Inhibitors (e.g., Clarithromycin, Ketoconazole, Ritonavir) | Increase ketamine plasma levels, potentiating its effects and side effects. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | Decrease ketamine plasma levels, potentially reducing efficacy. | Moderate |
| Neuromuscular Blocking Agents (e.g., Succinylcholine, Vecuronium) | Ketamine may potentiate their neuromuscular blocking effect. May increase risk of bradycardia with succinylcholine. | Moderate |
| Halothane | Increased risk of bradycardia, arrhythmias, and reduced cardiac output. | Major |