Oxycodone is associated with dose‐dependent QTc prolongation in patients and low‐affinity inhibiting of hERG activity in vitro

WHAT IS ALREADY KNOWN

AIMS

During recent years some opioids have been associated with prolonged QT interval and torsade de pointes (TdP). In vitro patch clamp testing has shown that most opioids can block human ether‐a‐go‐go related gene (hERG) channels that are known to underlie cardiac repolarizing I_Kr current. This indicates that QT prolongation and TdP could be a more general problem associated with the use of these drugs. The aims of this study were to evaluate the association between different opioids and the QTc among patients and measure hERG activity under influence by opioids in vitro.

METHODS

One hundred chronic nonmalignant pain patients treated with methadone, oxycodone, morphine or tramadol were recruited in a cross‐sectional study. The QTc was estimated from a 12‐lead ECG. To examine hERG activity in the presence of oxycodone, electrophysiological testing was conducted using Xenopus laevis oocytes and HEK293 cells expressing hERG channels.

RESULTS

There were no differences in gender distribution or age between the treatment groups. The known association between methadone dose and QTc was confirmed (R² = 0.09; P = 0.02). Higher oxycodone dose was also associated with longer QTc (R² = 0.21; P = 0.02). A 100 mg higher oxycodone dose was associated with a 10 ms^1/2 (95% CI 2–19) longer QTc. Neither morphine nor tramadol dose was associated with the QTc. Electrophysiological testing revealed low‐affinity inhibition of the potassium current through hERG channels expressed in HEK293 cells (IC₅₀ = 171 µM oxycodone).

CONCLUSIONS

Among patients treated with methadone or oxycodone, higher doses were associated with longer QTc. Oxycodone is capable of inhibiting hERG channels in vitro.

DOI: 10.1111/j.1365-2125.2008.03327.x

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