Background: Ketamine, administered in subanesthetic doses, is an effective off-label treatment for severe and even treatment-refractory depression; however, despite dozens of studies across nearly 2 decades of research, there is no definitive guidance on matters related to core practice issues.
Methods: This article presents a qualitative review and summary about what is known about ketamine dosing, rate of administration, route of administration, duration of treatment, and frequency of sessions.
Results: Ketamine is most commonly administered in the dose of 0.5 mg/kg, but some patients may respond to doses as low as 0.1 mg/kg, and others may require up to 0.75 mg/kg. The ketamine dose is conventionally administered across 40 minutes; however, safety and efficacy have been demonstrated in sessions ranging between 2 and 100 minutes in duration. Bolus administration is safe and effective when the drug is administered intramuscularly or subcutaneously. Whereas the intravenous route is the most commonly employed, safety and efficacy have been described with other routes of administration, as well; these include oral, sublingual, transmucosal, intranasal, intramuscular, and subcutaneous routes. Patients may receive a single session of treatment or a course of treatment during the acute phase, and treatment may rarely be continued for weeks to years to extend and maintain treatment gains in refractory cases. When so extended, the ideal frequency is perhaps best individualized wherein ketamine is dosed a little before the effect of the previous session is expected to wear off.
Conclusions: There is likely to be a complex interaction between ketamine dose, session duration, route of administration, frequency of administration, and related practice. Until definitive studies comparing different doses, rates of administration, routes of administration, and other considerations are conducted, firm recommendations are not possible. From the point of view of clinical practicability, subcutaneous, intranasal, and oral ketamine warrant further study. If domiciliary treatment is considered, the risk of abuse must be kept in mind.
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