Time to Pain Relief After Immediate-Release Morphine in Episodic Pain

Sublingual Versus Swallowed Morphine: A Comparison

BACKGROUND

The optimal route for immediate-release morphine administration is controversial. The known physical characteristics of morphine that allow absorption are counter to the unproven belief that sublingual morphine is absorbed more quickly.

OBJECTIVE

The aim of this study was to compare swallowed and sublingual morphine for effects on plasma morphine concentrations (PMCs), pain relief, and taste.

METHODS

Ten participants with cancer (mean age, 50 ± 12 years) received a 10-mg morphine tablet in a randomized crossover design with repeated premeasure and postmeasure for 60 minutes. Measures included PMC and visual analog scale (100 mm) scores for pain relief and taste.

RESULTS

Interindividual variability in maximum PMC was 25-fold (2.2-55 ng/mL). At 60 minutes, sublingual and swallowed routes were not significantly different for mean area under the curve for PMC (swallowed, 329 ± 314 ng/mL; sublingual, 314 ± 299 ng/mL) or for mean pain relief scores (swallowed, 81 ± 32; sublingual, 78 ± 31). Taste scores at 5 (P < .05), 10 (P < .04), 15 (P < .02), and 20 (P < .04) minutes after swallowed doses were significantly less unpleasant than after sublingual doses.

CONCLUSION

In this crossover design, between-group PMCs were similar for sublingual and swallowed morphine and resulted in a similar level of pain relief. Given the 25-fold across-participant differences in PMC after the same dose, additional research is warranted to identify the sources of this tremendous variability in PMC.

IMPLICATIONS FOR PRACTICE

Because of unpleasant taste, which could influence adherence and subsequent analgesia, clinicians should encourage patients to swallow their morphine doses and restrict use of sublingual morphine to individuals who are unable to swallow.

End-of-dose pain in chronic pain: does it vary with the use of different long-acting opioids?

A large percentage of patients with chronic pain on around-the-clock (ATC) opioids may experience increased pain occurring at the end of a scheduled dose, also known as end-of-dose pain. Despite the significant prevalence and impact of end-of-dose pain in patients using extended-release (ER) opioids, there are no detailed analyses examining how the frequency of end-of-dose pain is linked to the formulations of long-acting opioids. Consequently, we performed a systematic review to evaluate how many published studies on patients with chronic cancer or noncancer pain identified end-of-dose pain. As only a few studies mentioned end-of-dose pain explicitly, we used breakthrough pain (BTP) as a surrogate parameter. We determined if any opioid formulation had a greater association with the frequency of BTP, the use of rescue medication for BTP, and the frequency of end-of-dose pain. Of the 39 studies entered in the final analysis, 14 studies across different formulations showed that ER opioids were effective in the prevention of BTP. The opioids most frequently studied were hydromorphone (26%), followed by morphine (23%), and transdermal buprenorphine (23%). Only 5% of the studies used immediate-release preparations. Overall, most studies showed that patients using ER preparations experienced fewer episodes of BTP compared with patients on placebo or an active comparator. This could reflect the favorable duration of action of these opioids compared with short-acting formulations. Future studies should examine the incidence of end-of-dose pain and use of rescue medicine in a longitudinal manner in patients with chronic pain taking short- vs. long-acting ATC opioids.

Management of breakthrough pain due to cancer

Breakthrough pain is defined as the transient exacerbation of pain occurring in a patient with otherwise stable, persistent pain. It is estimated to affect over 50% of patients, particularly those with moderate to severe background pain. Breakthrough pain is one of the most difficult pain syndromes to treat. There are several types of breakthrough cancer pain: incidental type involves flares of pain associated with movement or activity; idiopathic type is transitory pain unrelated to a specific activity; and in end-of-dose failure pain occurs when blood levels of medications fall below an analgesic threshold at the end of a dosing interval. Persistent and breakthrough pain are distinct components of cancer pain and require separate management. Successful management of breakthrough pain may require a combination of pharmacological and non-pharmacological treatment strategies. Supplemental analgesia, known as rescue medication, is a common pharmacological treatment option. Breakthrough pain is treated with supplemental short-acting opioid use, as needed, e.g. short-acting morphine, intranasal fentanyl and buccal tablets of fentanyl.