Substance Use

Medical Cannabinoids Systematic Review

Yet another review weighs in to dispel hype and marketing from the huge cannabis industry.

The conclusion is: There is reasonable evidence that cannabinoids improve nausea and vomiting after chemotherapy. They might improve spasticity (primarily in multiple sclerosis). There is some uncertainty about whether cannabinoids improve pain, but if they do, it is neuropathic pain and the benefit is likely small. Adverse effects are very common, meaning benefits would need to be considerable to warrant trials of therapy.

No matter, the anecdotal based evidence will continue to be pushed by vested interests.

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Ultrarestrictive Opioid Policy

This study in gynecologic oncology surgery implemented a policy whereby patients undergoing ambulatory or minimally invasive surgery (laparoscopic or robotic approach) were not prescribed opioids at discharge unless they required more than 5 doses of oral or intravenous opioids while in the hospital, and patients who underwent a laparotomy were provided a 3-day opioid pain medication supply at discharge.

Importantly the reduction in opioid use was not accompanied by an increase in pain scores. Such policies mirror the use of opioid free (or sparing) anesthetic techniques which are increasingly employed. 

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Buprenorphine Peri-Operatively

A review on managing Buprenorphine in the perioperative period notes the disparate views and protocols in use ranging from continuing it to weaning off and replacing with full agonists. The overall conclusion is that the ‘main impetus for discontinuation, i.e., inadequate pain management, may be based on expert opinion and not on the existing evidence’…”no evidence against continuing buprenorphine perioperatively, especially when the dose is < 16 mg SL daily.

The authors recommend that future studies require standardized reporting of median doses, details on the route of delivery, dosing schedules and any dosing changes, and rates of addiction relapse, including long-term morbidity and mortality where possible”.

Consultation with the prescribing expert in substance use would seem highly advisable when such patients present to us to balance the probable greater need for analgesics with safety and relapse potential.

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Ketamine for Depression

Ketsmine has recently enjoyed a surge in popularity in Anesthesia and Emergency Medicine as part of multimodal anesthesia/analgesia and for opioid sparing respectively. In addition, Ketamine clinics are appearing for regular Ketamine treatments for refractory depression. Postulated mechanisms include NMDA antagonism, catecholamine effects, anti-inflammatory or opioid receptor effects.  While there is some evidence of short and medium term beneficial effect, much remains to be elucidated and the practice may be ahead of the evidence for this off-label use. More evidence is also needed about potential side effects, like dependence, hepatic, cognitive and renal effects, especially the severe intractable bladder dysfunction reported in recreational users. This article reviews Ketamine’s use for depression.

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Cannabinoids for Pain

The British Pain Society adds a rational voice to the debate and hype re cannabis and cannabinoids for pain. It confirms what studies and meta-analyses have generally found, that the evidence base for effectiveness is weak. Concerns are expressed for potential side effects especially in terms of misuse, and effects on cognition and mental health (experts have consistently warned on the dangers in teenagers and use during pregnancy).

The Society feels that there is no evidence to support routine use in pain management but acknowledges their use when other modalities fail, and provides strict advice on monitoring and supporting such patients, with a plan to withdraw them when shown ineffective.

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Acute Pain in Buprenorphine-Maintained Patients

Buprenorphine is increasingly encountered as a maintenance agent in substance use disorders rather than Methadone. Analgesia in such patients is challenging due to the complex partial agonist and antagonist properties of this agent.  Strategies include continuing buprenorphine for minor surgeries – often dividing the daily dose, or stopping it before surgery and using other opioids for analgesia in major surgery.

This study found that in those maintained on 12-16mg daily with last dose c. 17 hours ago,  up to 32mg of either IV Hydromorphine or Buprenorphine was effective. “However, the use of hydromorphone for analgesia in buprenorphine-maintained individuals confers greater abuse liability and side effects than does supplemental intravenous buprenorphine”. Analgesia requirement, side effects, drug interactions and factors like whether Buprenorphine is stopped or continued must all be taken into account.

Discontinuing Long-term Opioids in Chronic Pain

Judicious weaning and even discontinuing long term opioids in chronic pain is an option to discuss with patients. Whereas pain may not be fully controllable, quality of life is just as important and that includes the potential harms of opioids – addiction, overdose and death, falls, fractures, constipation, reduced libido, infertility, osteoporosis, sleep-disordered breathing, depression and motor vehicle accidents (link)

This retrospective review suggests that pain is no worse after discontinuing long term opioids especially in mild or moderate pain and may in fact slightly improve. Mechanisms involved may include tolerance and/or hyperalgesia.  The authors caution that nonetheless such patients may remain at risk for mental illness or suicide and careful psychosocial follow up is mandatory, as well as multimodal pain management strategies including non-pharmacological methods.

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