Ketamine with Gabapentin

Ketamine + Gabapentin can cause:

1. Neurochemical interactions: Ketamine blocks NMDA receptors (especially on interneurons, leading to an increase in glutamatergic AMPA activity) and has a slight affinity for opioid receptors. Gabapentin binds to the α₂δ subunit of Ca²⁺ channels and thereby enhances the GABAerg inhibitory effect (reduces glutamate release). The mechanisms of action are therefore different. There is no known direct pharmacodynamic interaction between NMDA blockade and GABA modulation. Theoretically, gabapentin acts complementarily as an additional inhibitor, whereas ketamine produces stimulating glutamate effects.

2. Therapeutic effect: Both agents have analgesic and sedative properties. In the context of depression or PTSD, gabapentin can promote sleep and relaxation, while ketamine has a rapid antidepressant effect. A few case reports suggest that both ketamine and gabapentin can contribute to the treatment of chronic pain and anxiety. There appears to be no negative effect on each other's antidepressant action; some clinical experiences show no diminished effect when they are combined. However, gabapentin may alleviate potential mental side effects of ketamine.

3. Danger or risks: Case reports show that there is little evidence of additive CNS depression. A public report (case report) concludes that gabapentin and ketamine not significantly synergistic cause respiratory depression or sedation. Nevertheless, caution is always advised: both substances cause dizziness and coordination disorders, so when combined there is a risk of falls or confusion. Overdosing on gabapentine can lead to bradycardia and hypoventilation, and ketamine can cause hallucinations or tachycardia; the combined occurrence of these effects is rare but possible. Serotonin syndrome is not an issue, as neither substance acts serotonergically. In practice, ketamine is used without stopping gabapentine, as there are no serious contraindications. However, a short discontinuation period of gabapentine may sometimes be preferred.