European Pain Management Discussion Forum

ABSTRACT

Queries from European physicians about analgesic pharmacotherapy and responses from the author are presented. The topics addressed in this issue pertain to fibromyalgia, adverse effects of opioids, and the identification and management of restless leg syndrome.

KEYWORDS :

• Adverse effects
• central sensitization
• fibromyalgia
• opioids
• restless leg syndrome

QUESTION

Is there a difference in the degree of tolerance to the side effects of opioids?

ANSWER

Opioids have numerous potential adverse effects (AEs), (1) some of which are common, such as drowsiness, dizziness, nausea, and bowel dysfunction, including constipation. Less common AEs include itch, confusion, perspiration, urinary retention, respiratory depression, and dependence. Some AEs tend to decline over time, whereas others do not. Studies on opioid-induced constipation, which appears to be the most prevalent AE, clearly show that it does not decline over time. In contrast, nausea, drowsiness, and dizziness usually appear soon after treatment initiation or dose escalation and lessen over time. The same is true for respiratory depression. This rare yet serious AE has been reported in the context of acute pain management, but is not a problem in chronic opioid therapy. No tolerance is expected in the case of itch, confusion (especially in elderly patients), perspiration, and urinary retention.

QUESTION

An otherwise healthy, 45-year-old woman has an uncomfortable sensation in her legs, especially at night, which is somewhat relieved by moving her legs. Nerve conduction tests ruled out neuropathy, and lumbar spine imaging was normal. What might cause this?

ANSWER

The most likely diagnosis is restless leg syndrome (RLS). RLS is characterized by painful legs, typically noticeable at rest, which eases with motion of the legs. Patients may also describe it as an irresistible urge to move the legs at night. RLS usually progresses slowly.

Its pathophysiology is unclear although it has been associated with conditions such as pregnancy, iron deficiency, and chronic renal failure, and various medications (antiemetics, antihistamines, and others). A family history is reported in more than half of patients, suggesting a genetic form of the disorder (1).

Although it is not uncommon, RLS is thought to be underdiagnosed, as there is no single diagnostic test and it has to be diagnosed clinically, based on history and symptoms. Treatment consists of managing any associated medical condition; decreasing or eliminating consumption of caffeine, alcohol, and tobacco (2); and medication, usually dopaminergic agents (1).