Intranasal Ketamine May Be an Alternative to IV in Refractory Depression
At the 2013 meeting of the American Academy of Child and Adolescent Psychiatry, Kyle Lapidus of Mount Sinai Hospital reviewed the literature from controlled studies on the efficacy of intravenous (IV) ketamine at a dosage of 0.5 mg/kg over a 40-minute infusion for adults with treatment-resistant depression (with consistent response rates of 50% or more), and suggested that intranasal ketamine may also be effective.
Ketamine is a strong blocker of the glutamate NMDA receptor. At high doses (6 to 12 mg/kg) it is an anesthetic, at slightly lower doses (3 to 4 mg/kg) it is psychotomimetic (causing psychotic symptoms) and is sometimes used as a drug of abuse, and at very low doses it is a rapidly acting antidepressant, often bringing about results within 2 hours. Antidepressant effects typically last 3 to 5 days, so the question of how to sustain these effects is a major one for the field.
Murrough et al. reported in Biological Psychiatry in 2012 that five subsequent infusions of ketamine sustained the initial antidepressant response and appeared to be well tolerated by the patients. Another NMDA antagonist, riluzole (used for the treatment of ALS or Lou Gehrig’s disease), did not sustain the acute effects of ketamine, and now lithium is being studied as a possible strategy for doing so.
The bioavailability of ketamine in the body depends on the way it is administered. Compared to IV administration, intramuscular (IM) administration is painful but results in 93% of the bioavailability of IV ketamine. Intranasal (IN) administration results in 25-50% of the bioavailability of IV administration, while oral administration results in only 16-20% of the bioavailability of IV administration, so Lapidus chose to study the IN route. He compared intranasal ketamine at doses of 50mg (administered in a mist ) to 0.5 ml of intranasal saline. Both were given in two infusions seven days apart. Lapidus observed good antidepressant effects and good tolerability. Papolos et al. had reported earlier that intranasal ketamine had good effects in a small open trial in treatment-resistant childhood onset bipolar disorder.
Editor’s Note: Further studies of the efficacy and tolerability of intranasal ketamine are eagerly awaited.
