Background and Importance Chronic pain lasts more than three months and includes primary and neuropathic pain. Ketamine provides analgesia and amnesia at a subanaesthetic dose, therefore proposing its use as chronic pain treatment when it is refractory to the standard based on tricyclic antidepressants (TCAs), gabapentinoids, and opioids.
Aim and Objectives To analyse the use of an oral formulation of ketamine prepared and dispensed by hospital pharmacy at a third-level hospital in chronic refractory pain (CRP) treatment.
Material and Methods Observational retrospective study including a cohort of patients with CRP treated with an oral 10 mg/ml ketamine solution at a third-level hospital between January 2021 to December 2021. All of them signed informed consent. A tolerance test with intravenous ketamine was performed on every patient before initiating treatment. Data were collected from clinical history and pharmacy programs. For statistical analysis, continuous variables were categorised according to median (range) or percentage values.
Results 30 patients were included (67% men, median age 48.5 years (18–73)). Chronic pain type was neuropathic in all cases, cancer-associated (37%), trauma-caused neuronal damage (33%), demyelinating (17%), and 14% to other causes. Patients received oral ketamine during a median of 20 months (1–58) and daily dosage varied from 40 mg to 150 mg, the most frequent being 60 mg/d (40%), 90 mg/d (27%) and 120 mg/d (23%). 80% were in adjuvant treatment with opioids; of them, 88% took major opioids. 40% had reached the therapeutic limit by being treated with opioids, TCAs and gabapentinoids without any differences in pain origin. 43% had not included TCAs in treatment.
Treatment was discontinued in 5 patients (17%); 4 due to adverse effects (dizziness, cognitive alterations, tachycardia, hypertension), and 1 due to death unrelated to treatment.
Conclusion and Relevance This study shows oral ketamine analgesic use in neuropathic CRP treatment at 40–150 mg/d; the most frequent 60 mg/d and 90 mg/d. Inferior to those referred to in the literature (up to 400 mg/d). Good tolerance and an acceptable safety profile were observed (17% discontinued) without serious adverse events. As to adjuvant treatment, 80% received opioids and 40% the combination of opioids, gabapentinoid, and TCAs. More studies are needed to evaluate the long-term effectiveness and safety of oral ketamine treatment and to position it in CRP management.
Conflict of Interest No conflict of interest
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