Abstract
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.