Evaluating oral ketamine's adverse side effects in chronic pain patients

Ketamine has been shown to be an effective treatment at sub-anesthetic doses for various chronic pain conditions. This study assesses the relationship between oral ketamine and the incidence of adverse side effects in patients receiving long-term, moderate to high-dose tablets for chronic pain.

All adult patients given prescriptions for oral ketamine from November 2019 to October 2023 were identified for our initial cohort. Patients were excluded if they failed to reach at least 80 mg per day during their treatment period or if their treatment periods lasted less than 90 days. Demographic variables, comorbidities, prescription information, and patient-reported side effects were recorded.

This study identified 193 patients who received oral ketamine prescriptions at our institution. One hundred forty-nine patients received 80 mg-159 mg per day, 24 patients received 160 mg-199 mg per day, and 20 patients received 200 mg-240 mg per day. In Group 1, 9 of the 149 patients (6.0%) reported 12 instances of side effects; in Group 2, 2 of the 24 patients (8.3%) reported 6 instances of side effects; in Group 3, 2 of the 20 patients (10%) reported 2 instances of side effects. The maximum average daily dosage was not associated with the number of reported side effects (P = 0.10). Age was the only covariate associated with the number of adverse side effects (P = 0.04).

Our results suggest that at daily doses above 80 mg and up to 240 mg, oral ketamine does not show a dose-dependent relationship in predicting the number of patient-reported side effects.