Long-term safety and efficacy of sublingual ketamine troches/lozenges in chronic non-malignant pain management.

Abstract

Chronic non-malignant pain is a disabling condition that results in a reduction in function and quality of life when inadequately managed. Sublingual ketamine has been shown to be efficacious for use in chronic pain. Despite its use for decades in chronic non-malignant pain, there is no published long-term data on safety, side-effects or adverse drug reactions. The aim of this case-series is to provide the initial evidence for safety and efficacy in this patient group. We present a retrospective review of 29 (n = 29) patients from a metropolitan tertiary pain service who have been receiving sublingual ketamine troches/lozenges between the period of 2012 and 2019. Patients were identified from the outpatient pain clinic, who had been admitted for inpatient subcutaneous ketamine infusions as part of opiate detoxification or management of central sensitisation due to a chronic neuropathic pain syndrome. An initial review was performed to check the patient started taking the ketamine troches. Each of these medical records was reviewed manually to extract information to a datasheet. There was a wide range of dosages used from 25 to 600 mg in divided doses. The duration of treatment ranged 2-89 months. There was no association with either the dosage or duration of treatment and frequency of side-effects. There was an overall reduction in the use of opioids, gabapentinoids or benzodiazepines in 59% of patients with 39% having a complete cessation of an analgesic agent. Side-effects were reported in 24%, but only 7% discontinued the treatment due to the side-effect (drowsiness). There were no reports of renal impairment, cystitis or hepatotoxicity. This retrospective case-series has demonstrated that sublingual ketamine is a safe and effective analgesic agent to use in chronic non-malignant pain management. It is indicated in a variety of chronic pain conditions and has an excellent safety profile, with no association between the frequency in side-effects and duration of therapy or total daily dosages. The study has also shown that the 'safe' dose may be higher than the previous consensus.