The ‘dark side’ of adjuvant analgesic drugs

Amitriptyline in Neuropathic Cancer Pain in Patients on Morphine Therapy: A Randomized Placebo-controlled, Double-blind Crossover Study

Aims and Background

Amitriptyline is the most common analgesic adjuvant used in cancer patients with neuropathic pain, even though no specific studies have demonstrated a benefit. A randomized placebo-controlled, double-blind crossover study was designed to evidence the effects of amitriptyline in patients with neuropathic cancer pain.

Methods

Sixteen advanced cancer patients with neuropathic pain on systemic morphine therapy, no longer receiving oncologic treatment, presenting moderate pain (about 4 or more, but less than 7, on a numerical scale of 0-10) in the last week, and given a stable morphine dose in the last 2 days were admitted to the study. During the first week of study, patients were administered 25 mg of amitriptyline or equivalent drops of placebo at night for 3 days and 50 mg for the following 4 days. Doses for patients aged more than 65 years were 15 mg (first 3 days) and 30 mg (3 days after). After a week, a crossover took place for the second week, with the other treatment at an inverse sequence. Opioid consumption, pain intensity, symptoms and adverse effects, mood, sleep, patient's preference, quality of life before starting the study, the first week after and the second week after were recorded.

Results

No significant benefits in analgesia were found in the global pain intensity of the previous week of treatment, the least pain intensity or the pain evaluated just after a week of treatment, at the moment of the visit, when amitriptyline was compared with placebo. A significant difference was evidenced for the worst pain (P < 0.035). No differences in opioid doses during the period of study were found. Drowsiness, confusion and dry mouth were significantly more intense with amitriptyline than with placebo (P < 0.036, 0.003, and 0.034, respectively). There were no substantial differences between the two treatments in Spitzer's quality of life score and for each item. No differences in patients' preference for the two treatment periods were found. The analgesic effects of amitriptyline were slight and associated with adverse effects.

Conclusions

In light of the results obtained in the study, the extensive use of the drug for cancer pain should be questioned.

The panorama of opioid-related cognitive dysfunction in patients with cancer: a critical literature appraisal

BACKGROUND

Opioids have an essential role in the management of pain in cancer patients, particularly those with advanced disease. Cognitive dysfunction is a recognized complication of opioid use. However, misconceptions and controversy surround the nature and prevalence of its occurrence. A projected increase in the aging cancer population highlights the need for a better understanding of this phenomenon.

METHODS

A critical appraisal of the literature evidence in relation to the pattern, pathophysiology, assessment, impact, and management of cognitive dysfunction due to opioid use in cancer pain management is given.

RESULTS

Studies in cancer patients with less advanced disease reveal subtle evidence of cognitive impairment, largely related to initial dosing or dose increases. In advanced cancer, opioid-induced cognitive dysfunction usually occurs in the form of delirium, a multifactorial syndrome. The presence of both cognitive impairment and delirium frequently is misdiagnosed or missed. Potential risk factors include neuropathic and incidental pain, opioid tolerance, somatization of psychologic distress, and a history of drug or alcohol abuse. Elevation of opioid metabolites with renal impairment may contribute to cognitive dysfunction. Recognition of opioid-related cognitive dysfunction is improved by objective screening. Successful management requires either dose reduction or a change of opioid, in addition to addressing other reversible precipitants such as dehydration or volume depletion.

CONCLUSIONS

Opioid-related cognitive dysfunction tends to be subtle in the earlier stages of cancer, whereas delirium, a more florid form with behavioral disturbance is likely to be present in the advanced cancer population. In patients with advanced disease, an optimal management approach requires careful clinical assessment, identification of risk factors, objective monitoring of cognition, maintenance of adequate hydration, and either dose reduction or switching to a different opioid.

The uses of psychotropics in symptom management in advanced cancer

Approximately 50% of patients diagnosed with cancer die because of progressive disease. Psychotropic drugs are frequently used for the management of physical and psychosocial symptoms in these patients. Thalidomide, cannabinoids and melatonin are emerging agents for the management of cachexia. Psychostimulants have a defined role in the management of opioid-induced sedation. Haloperidol, tricyclic anti-depressants and newer anti-depressants also have an established role in the management of neuropsychiatric symptoms such as delirium or depression. Cancer patients present unique challenges for successful psychotropic therapy including older age, malnutrition, autonomic failure, borderline cognition, opioid and psychotropic therapy. A practical clinical approach which defines a specific target symptom, an outcome latency period, expected side effects, and reviews possible drug interactions, and frequent monitoring is outlined. Continued research is needed to further define the role of psychotropics in the management of the different physical and psychosocial symptoms in advanced cancer patients.